簡評:以雷射燒烤矽晶表面創造"針狀抗反射結構"...好技術--但是貴!
Aug. 4, 2008
Solar cells of the future may look totally black to the human eye because they absorb light so efficiently. That's the promise of new research from an interdisciplinary team at the University of Virginia being funded by a new U.Va. Collaborative Sustainable Energy Seed Grant worth about $30,000.While current solar cells reflect about 30 percent of the light energy that reaches their surface, the U.Va. team will use lasers to create tiny nanoscale surface textures that reduce that energy loss to less than 1 percent, over the entire solar spectrum and irrespective of the angle at which sunlight strikes the cell.While increasing the ultimate efficiency of solar cells, this laser texturing process could also drive down manufacturing costs. Because lasers are already used in the manufacturing of solar cells, the texturing process can be automated, eliminating the need for dangerous chemical treatments currently used to reduce reflectance.Team member Mool C. Gupta, a professor of electrical and computer engineering, developed this laser texturing process, patented through the U.Va. Patent Foundation. The resulting texture of 'nanospikes,' said Gupta, is like the sand on sandpaper — the added hills and valleys greatly increase the surface area and reduce the reflection of light. However, the 'nanospikes' are many times smaller than the sand of sandpaper (nanospikes range in height from 10 to 100 millionths of a meter) and are more precisely shaped.The 30 percent gain in light absorption from the nanospike surface may enable the creation of solar cells that are ultimately 2 percent to 3 percent more efficient than current technology, Gupta said. That may not sound like much, but "in the solar industry a 1 percent efficiency improvement is a big deal," noted Gupta, who is also the director of the National Science Foundation's Laser Industry/University Cooperative Research Center. "I'll be happy if we can get 2 to 3 percent more efficiency."Such incremental gains in efficiency and reduced manufacturing cost are helping drive the rapid growth of solar energy, a market that is growing about 40 percent per year in recent years, spurred in part by rising oil prices, Gupta said.Even with such rapid growth, solar power still only accounts for a tiny fraction of the world energy supply. "It's not like solar is trying to take the place of oil," Gupta said. "But if, in 20 to 30 years, solar can provide 5 to 10 percent of the world energy supply, then solar would be a huge industry – bigger than the entire microelectronics industry," which includes all the computer chips in today's cars, phones, appliances and buildings, as well as the chips in computers.Gupta's U.Va. partners in this research are Keith Williams, an assistant professor of physics with expertise in measuring the characteristics of surfaces, and Joe Campbell, a professor of electrical and computer engineering, member of the National Academy of Engineering and an expert in optics and electronics fabrication.Gupta's team will use the research results enabled by this seed grant to create a better application for larger grants from the Department of Energy and the National Science Foundation. "It's important to have some initial data to demonstrate the promise of the research, beyond just a theory," said Gupta, who hopes that his tiny 'nanospikes' can be a part of the solutions to the grave energy issues of our time. "The scientific community really needs to gear up to address energy issues that have a big impact on our society."
2008年7月29日 星期二
Novel industrial approaches in solar-cell production
簡評:
Scribing is required to obtain a monolithic series connection of modules.6 This essential technology has both allowed economically feasible solar-cell production and enabled the strong growth market for thin-film photovoltaic applications. Thin-film solar cells can be made using different material combinations. The substrate can either be glass, plastic foil, or metal foil. Generally, the cell itself consists of a back contact, a front-contact layer, and an absorber material in between. For the contacts, transparent conductive oxides (TCOs) or metals are used. Commonly used absorber materials include silicon, cadmium telluride, copper-indium di-selenide (CIS), and other combinations with copper indium, such as CIGS or CIGSSe. The layers are typically up to several microns thick. In Figure 4, a thin-film solar-cell cross-section is shown. Common referencing to the laser processes includes ‘patterning 1’ or P1 for the first contact, P2 for the absorber, and P3 for the second contact.
Thin-film solar-cell scribing is, in essence, based on the different transmissivities of the film materials at the laser wavelengths used. The deposition and scribing processes are shown schematically in Figure 5. The first TCO layer deposited can be zinc oxide, tin dioxide, or indium-tin oxide. Usually, when glass is used as the substrate, scribing is done from the glass side. An example is shown in Figure 6. Silicon as the absorber material is usually scribed with a laser wavelength of 532nm. For this setup, TCO is transparent, and silicon absorbs radiation in a thin layer. Scribing of the third layer can be done using the same laser wavelength as for the absorber. In this case, the second absorption layer is also removed. This is not necessary, but it does not affect the solar-cell function either.
In summary, the role of laser technology in the solar photovoltaic industry is gaining importance. Laser applications enable economic and technical feasibility of new design concepts. To achieve the required performance quality in acceptably short processing times, further technological system development is necessary. Both system and process development of newly emerging laser sources and their applications are the subject of future research at our institute.
雷射在太陽能電池產業的用途,請多參考--本資料很有用處!
------------------------------
Aart Schoonderbeek and Andreas Ostendorf
Laser technology applications are indispensable in the photovoltaic industry, allowing both enhanced energy-generating efficiency and reduced costs.
The photovoltaic industry has experienced enormous growth in recent years. However, for solar-cell technology to become competitive in the long term, both an increase in energy-generating efficiency and a reduction in production costs is required. Several laser applications for solar-cell production are shown in Figure 1, of which three—hole drilling for back-contacted solar cells, silicon dioxide (SiO2) removal for making grooves, and scribing of thin-film cells—are described here in more detail.
Hole drilling for back-contacted cells
Laser drilling is a key technology used in many new back-contact solar-cell production concepts because alternative economically feasible drilling processes are not yet available.1–4 Square 6in-wide (156×156mm2) and 250μm−thin wafers are standard in industry. Common industrial photovoltaic cells have a screen-printed contact layer on the front, which blocks 5–7% of the incoming light by shadowing. To overcome this performance degradation, many new cell concepts are being developed, usually with the emitter contact either completely or partially on the rear. This results in higher cell efficiencies for energy generation. For these emitter wrap-through (EWT) cells, laser drilling is the only suitable method to create the necessary holes from the front to the back. Typically, a drilling efficacy of 15,000 80μm-diameter holes is required.1 Figure 2 shows a typical hole. Up to several thousand holes can be drilled per second.
Laser drilling is a key technology used in many new back-contact solar-cell production concepts because alternative economically feasible drilling processes are not yet available.1–4 Square 6in-wide (156×156mm2) and 250μm−thin wafers are standard in industry. Common industrial photovoltaic cells have a screen-printed contact layer on the front, which blocks 5–7% of the incoming light by shadowing. To overcome this performance degradation, many new cell concepts are being developed, usually with the emitter contact either completely or partially on the rear. This results in higher cell efficiencies for energy generation. For these emitter wrap-through (EWT) cells, laser drilling is the only suitable method to create the necessary holes from the front to the back. Typically, a drilling efficacy of 15,000 80μm-diameter holes is required.1 Figure 2 shows a typical hole. Up to several thousand holes can be drilled per second.
Figure 1. Laser applications for solar-cell production: hole drilling of back-contact solar cells, SiO2 removal for groove production, laser welding/soldering of contacts, edge isolation, wafer cutting, removal of dielectric layers for improved contact performance, texturing to increase the absorption of sunlight and therefore to enhance the efficiency of the cell, scribing of thin-film cells, and edge deletion.
Figure 2. A typical hole drilled with a pulsed-fiber laser, characterized by a burst of 20 pulses and a pulse energy of 1mJ (after etching). A human hair illustrates the small diameter of the holes.
SiO2 removal for grooves
For wafer-based solar cells, grooves are used in several novel designs.1,5 Grooves typically have a depth of up to several tens of microns. The groove is obtained in two steps. First, a barrier layer, such as SiO2 or silicon nitride (SiNx), is removed using a laser beam. Subsequently, a chemical etching process is applied to remove the laser-damaged silicon and to obtain the desired depth. The residual SiO2 or SiNx layer functions as a barrier during the etching process. Figure 3 shows a typical groove result.
For wafer-based solar cells, grooves are used in several novel designs.1,5 Grooves typically have a depth of up to several tens of microns. The groove is obtained in two steps. First, a barrier layer, such as SiO2 or silicon nitride (SiNx), is removed using a laser beam. Subsequently, a chemical etching process is applied to remove the laser-damaged silicon and to obtain the desired depth. The residual SiO2 or SiNx layer functions as a barrier during the etching process. Figure 3 shows a typical groove result.
Figure 3. Groove processed with an excimer laser at a wavelength of 248nm. The rectangular laser spot is shown in the processed area. The groove depth is about 20μm. The laser-processed surface is smooth after chemical etching, and does not contain any debris.
Figure 4. Cross-section of a thin-film solar cell (not to scale). The layers are typically up to several microns thick. The different layers, P1–P3 (transparent conductive oxides or absorber material), are successively deposited and scribed during the production process. The current flow is shown by the arrows.
Figure 5. Deposition and scribing for a thin-film solar cell. (1) Substrate, (2) TCO deposition, (3) P1 TCO scribing, (4) absorber deposition, (5) P2 absorber scribing, (6) TCO deposition, and (7): P3 TCO scribing.Scribing of thin-film cells
Scribing is required to obtain a monolithic series connection of modules.6 This essential technology has both allowed economically feasible solar-cell production and enabled the strong growth market for thin-film photovoltaic applications. Thin-film solar cells can be made using different material combinations. The substrate can either be glass, plastic foil, or metal foil. Generally, the cell itself consists of a back contact, a front-contact layer, and an absorber material in between. For the contacts, transparent conductive oxides (TCOs) or metals are used. Commonly used absorber materials include silicon, cadmium telluride, copper-indium di-selenide (CIS), and other combinations with copper indium, such as CIGS or CIGSSe. The layers are typically up to several microns thick. In Figure 4, a thin-film solar-cell cross-section is shown. Common referencing to the laser processes includes ‘patterning 1’ or P1 for the first contact, P2 for the absorber, and P3 for the second contact.
Thin-film solar-cell scribing is, in essence, based on the different transmissivities of the film materials at the laser wavelengths used. The deposition and scribing processes are shown schematically in Figure 5. The first TCO layer deposited can be zinc oxide, tin dioxide, or indium-tin oxide. Usually, when glass is used as the substrate, scribing is done from the glass side. An example is shown in Figure 6. Silicon as the absorber material is usually scribed with a laser wavelength of 532nm. For this setup, TCO is transparent, and silicon absorbs radiation in a thin layer. Scribing of the third layer can be done using the same laser wavelength as for the absorber. In this case, the second absorption layer is also removed. This is not necessary, but it does not affect the solar-cell function either.
Figure 6. Example of TCO scribing of P1 with a diode-pumped solid-state laser at a wavelength of 1047nm.
In summary, the role of laser technology in the solar photovoltaic industry is gaining importance. Laser applications enable economic and technical feasibility of new design concepts. To achieve the required performance quality in acceptably short processing times, further technological system development is necessary. Both system and process development of newly emerging laser sources and their applications are the subject of future research at our institute.
-------------------------------
About Writer
Aart Schoonderbeek
Production and Systems Department
Technologies for Non-Metals Group
Laser Zentrum Hannover e.V.
Hannover, Germany
http://www.lzh.de/
Aart Schoonderbeek obtained his PhD at the Netherlands Center for Laser Research in 2005, supported by the chairs of Applied Laser Technology and of Laser Physics and Nonlinear Optics, both at the University of Twente (Netherlands). He was subsequently employed as a research scientist at the Laser Zentrum Hannover. He works on process technologies for nonmetals, concentrating on laser processing of glass and silicon.
Production and Systems Department
Technologies for Non-Metals Group
Laser Zentrum Hannover e.V.
Hannover, Germany
http://www.lzh.de/
Aart Schoonderbeek obtained his PhD at the Netherlands Center for Laser Research in 2005, supported by the chairs of Applied Laser Technology and of Laser Physics and Nonlinear Optics, both at the University of Twente (Netherlands). He was subsequently employed as a research scientist at the Laser Zentrum Hannover. He works on process technologies for nonmetals, concentrating on laser processing of glass and silicon.
--------------------------------
References:
1. P. Engelhart, A. Teppe, A. Merkle, R. Grischke, R. Meyer, N.-P. Harder, R. Brendel, The RISE-EWT solar cell: new approach towards simple high efficiency silicon solar cells, Proc. 15th PVSEC, pp. 802-803, 2005.
2. J. M. Gee, W. K. Schubert, P. A. Basore, Emitter wrap-through solar cell, Proc. 23rd IEEE Photovolt. Specialists Conf., pp. 265-270, 1993.
3. F. Clement, M. Lutsch, T. Kubera, M. Kasemann, W. Kwapil, C. Harmel, N. Mingirulli, D. Erath, H. Wirth, D. Biro, R. Preu, Processing and comprehensive characterisation of screen-printed mc-Si Metal Wrap Through (MWT) solar cells, Proc. 22nd EU-PVSEC, pp. 1399-1402, 2007.
4. I. Romijn, M. Lamers, A. Stassen, A. Mewe, M. Koppes, E. Kossen, A. Weeber, ASPIRE: a new industrial MWT cell technology enabling high efficiencies on thin and large mc-Si wafers, Proc. 22nd EU-PVSEC, pp. 1043-1049, 2007.
5. K. C. Heasman, A. Cole, M. Brown, S. Roberts, S. Devenport, I. Baistow, T. M. Bruton, Process development of laser grooved buried contact solar cells for use at concentration factors up to 100x, Proc. 22nd EU-PVSEC, pp. 1511-1512, 2007.
6. S. Haas, A. Gordijn, H. Stiebig, High speed laser processing for monolithical series connection of silicon thin-film modules, Progr. Photovolt., pp. 195-203, 2007. doi:10.1002/pip.792
1. P. Engelhart, A. Teppe, A. Merkle, R. Grischke, R. Meyer, N.-P. Harder, R. Brendel, The RISE-EWT solar cell: new approach towards simple high efficiency silicon solar cells, Proc. 15th PVSEC, pp. 802-803, 2005.
2. J. M. Gee, W. K. Schubert, P. A. Basore, Emitter wrap-through solar cell, Proc. 23rd IEEE Photovolt. Specialists Conf., pp. 265-270, 1993.
3. F. Clement, M. Lutsch, T. Kubera, M. Kasemann, W. Kwapil, C. Harmel, N. Mingirulli, D. Erath, H. Wirth, D. Biro, R. Preu, Processing and comprehensive characterisation of screen-printed mc-Si Metal Wrap Through (MWT) solar cells, Proc. 22nd EU-PVSEC, pp. 1399-1402, 2007.
4. I. Romijn, M. Lamers, A. Stassen, A. Mewe, M. Koppes, E. Kossen, A. Weeber, ASPIRE: a new industrial MWT cell technology enabling high efficiencies on thin and large mc-Si wafers, Proc. 22nd EU-PVSEC, pp. 1043-1049, 2007.
5. K. C. Heasman, A. Cole, M. Brown, S. Roberts, S. Devenport, I. Baistow, T. M. Bruton, Process development of laser grooved buried contact solar cells for use at concentration factors up to 100x, Proc. 22nd EU-PVSEC, pp. 1511-1512, 2007.
6. S. Haas, A. Gordijn, H. Stiebig, High speed laser processing for monolithical series connection of silicon thin-film modules, Progr. Photovolt., pp. 195-203, 2007. doi:10.1002/pip.792
A cool light bulb
簡評:
這兩個高麗棒子的研究還真不賴!
------------------------------
Shawn-Yu Lin and Yong-Sung Kim
A photonic band-pass filter enclosing the filament recycles infrared emissions, reducing temperature and producing an eight-fold increase in energy efficiency.
Since the time of Thomas Edison, incandescent light bulbs have been the dominant light source for illumination. Today, incandescent bulbs still hold crucial advantages. They produce a warm white light and can be dimmed easily using inexpensive controls. They have a relatively inexpensive first-cost per lumen, a long-established infrastructure, and do not contain hazardous materials such as mercury. However, because of their relatively low energy efficiency, incandescent bulbs are being replaced rapidly in many areas. It is time to re-visit the fundamental limit of the incandescent bulb and to improve its efficiency.
Incandescent bulbs emit light in a manner closely resembling Plank's law of blackbody radiation. The law describes how a body capable of absorbing all radiation contacting it (a blackbody) will emit at a given range of wavelengths dependant on its temperature. The inefficiency inherent in an incandescent bulb is due to the fact that it emits both infrared and visible light at temperatures between 2000 and 3000K. Specifically, the infrared portion of the radiation consumes about 88% of the input electric energy and becomes wasted heat (see Figure 1). Hence, recycling infrared light into useful visible light would improve incandescent efficiency.
Figure 1. A blackbody radiation curve at T=2800K, which is a typical operating temperature of a 100W incandescent bulb. Approximately 88% of the light is emitted in the infrared region. BB: blackbody.
Recycling processes have previously been developed in the form of reflecting envelopes using either a dielectric metal film stack1,2 or a dielectric multi-layered film.3 However, for both structures the reflectance in the near-infrared region is not high enough to bounce back all the infrared light. To overcome these limitations, we employed a two-dimensional metallic photonic band gap (PBG) filter architecture to enclose the incandescent filament. The filter acts as a perfect transmitter for the useful visible light and a perfect reflector for the undesirable infrared light. The reflected light is re-absorbed which, in turn, helps to heat up the filament. This infrared recycling process has two major energy consequences. First, it reduces the amount of electricity required to maintain a hot filament and thus improves electric-to-optical conversion efficiency. Second, it reduces the thermal radiation of the bulb as infrared photons cannot escape. With this approach, the energy efficacy of an incandescent light bulb can be improved by as much as eight times. Accordingly, the cost of a million-lumen-hour is reduced to $1.00–$2.00. We used silver as the metallic material because it has a low intrinsic absorption in the visible and near infrared wavelengths. The low absorption of silver is key to simultaneously achieving a high transmittance in the visible and a high reflectance in the infrared regions. A metallic PBG filter is also more practical to use as it is robust against thermal stress at high temperatures.
Figure 2. (a) The photon recycling scheme. (b) Schematic of the 2D metallic photonic crystal where 'a' is the pitch, 'd' is the size of the air opening, 'w' is the bar width, and 'h' is the thickness. Silver is used as the metal due to its low absorption in the visible and near infrared wavelengths. rf: radius of the filter. rb: radius of the blackbody filament, here a sphere.
To illustrate the validity of our approach, we have employed an ideal system that has a spherical blackbody filament enclosed by the filter: see Figure 2(a). The maximum luminous efficacy reaches 125lm/W. The details of the calculation were reported recently.4 For general purpose illumination, not only the efficiency but also the color quality is important in evaluating a bulb. The color quality of a bulb is commonly characterized by the correlated color temperature (CCT), used to categorize color tone, and the color rendering index (CRI), which measures the ability of a bulb to reproduce the true color of objects. If the CCT is lower than 3300K the color is categorized as a warm tone, whereas if the CCT is higher than 5300K the color is categorized as a cool tone. The CCT of our incandescent bulb did not exceed 3500K, indicating the filtered light is in the desired warm range. The CRI has a range between 0 and 100, with 0 being the minimum and 100 being the maximum color rendering capability. The color rendering index of our new light bulb is calculated to be between 68 and 90, better than that of a standard fluorescent lamp with a CRI of approximately 60.
Photon recycling via a metallic PBG filter is a promising new route to creating a ‘cool’ light bulb. Our next step is to study a cylindrical filter geometry that is comparable to the commonly used tungsten-filament configuration.
We would like to acknowledge the financial support of DOE-BES under grant number DE-FG02-06ER46347
------------------------
About Writer
Shawn-Yu Lin, Yong-Sung Kim
Physics
Rensselaer Polytechnic Institute
Troy, NY
Shawn-Yu Lin is an institute constellation professor and professor of physics at Rensselaer Polytechnic Institute. His expertise is in the interaction of light with hierarchy nanostructure. He is a fellow of the American Physical Society, a fellow of the Optical Society of America, and a distinguished member-of-technical-staff at Sandia National Laboratories
Yong Sung Kim specializes in electromagnetic wave modeling of three-dimensional photonic crystal structures including finite difference time domain, dispersion calculation and transfer matrix methods.
-------------------------------------------
References:
1. J. Brett, R. Fontana, P. Walsh, S. Spura, L. Parascandola, Development of high energy-conserving incandescent lamps, J., J. Illuminating Eng. Soc. 214, pp. 93, 1980.
2. R. Fontanta, I. Goldstein, L. Thorington, R. Howson, The design, construction and performance of an incandescent light source with a transparent heat mirror, Lighting Tech. 18, pp. 93, 1986.
3. R. Bergman, T. Parham, Application of thin film reflecting coating technology to tungsten filament lamps, IEE Proceedings-A 140, pp. 418, 1993.
4. Y. S. Kim, S. Y. Lin, A. Chang, J. H. Lee, K. M. Ho, Analysis of photon recycling using metallic photonic crystal, J. Appl. Phys. 102, pp. 063107, 2007.doi:10.1063/1.2779271
這兩個高麗棒子的研究還真不賴!
------------------------------
Shawn-Yu Lin and Yong-Sung Kim
A photonic band-pass filter enclosing the filament recycles infrared emissions, reducing temperature and producing an eight-fold increase in energy efficiency.
Since the time of Thomas Edison, incandescent light bulbs have been the dominant light source for illumination. Today, incandescent bulbs still hold crucial advantages. They produce a warm white light and can be dimmed easily using inexpensive controls. They have a relatively inexpensive first-cost per lumen, a long-established infrastructure, and do not contain hazardous materials such as mercury. However, because of their relatively low energy efficiency, incandescent bulbs are being replaced rapidly in many areas. It is time to re-visit the fundamental limit of the incandescent bulb and to improve its efficiency.
Incandescent bulbs emit light in a manner closely resembling Plank's law of blackbody radiation. The law describes how a body capable of absorbing all radiation contacting it (a blackbody) will emit at a given range of wavelengths dependant on its temperature. The inefficiency inherent in an incandescent bulb is due to the fact that it emits both infrared and visible light at temperatures between 2000 and 3000K. Specifically, the infrared portion of the radiation consumes about 88% of the input electric energy and becomes wasted heat (see Figure 1). Hence, recycling infrared light into useful visible light would improve incandescent efficiency.
Figure 1. A blackbody radiation curve at T=2800K, which is a typical operating temperature of a 100W incandescent bulb. Approximately 88% of the light is emitted in the infrared region. BB: blackbody.
Recycling processes have previously been developed in the form of reflecting envelopes using either a dielectric metal film stack1,2 or a dielectric multi-layered film.3 However, for both structures the reflectance in the near-infrared region is not high enough to bounce back all the infrared light. To overcome these limitations, we employed a two-dimensional metallic photonic band gap (PBG) filter architecture to enclose the incandescent filament. The filter acts as a perfect transmitter for the useful visible light and a perfect reflector for the undesirable infrared light. The reflected light is re-absorbed which, in turn, helps to heat up the filament. This infrared recycling process has two major energy consequences. First, it reduces the amount of electricity required to maintain a hot filament and thus improves electric-to-optical conversion efficiency. Second, it reduces the thermal radiation of the bulb as infrared photons cannot escape. With this approach, the energy efficacy of an incandescent light bulb can be improved by as much as eight times. Accordingly, the cost of a million-lumen-hour is reduced to $1.00–$2.00. We used silver as the metallic material because it has a low intrinsic absorption in the visible and near infrared wavelengths. The low absorption of silver is key to simultaneously achieving a high transmittance in the visible and a high reflectance in the infrared regions. A metallic PBG filter is also more practical to use as it is robust against thermal stress at high temperatures.
Figure 2. (a) The photon recycling scheme. (b) Schematic of the 2D metallic photonic crystal where 'a' is the pitch, 'd' is the size of the air opening, 'w' is the bar width, and 'h' is the thickness. Silver is used as the metal due to its low absorption in the visible and near infrared wavelengths. rf: radius of the filter. rb: radius of the blackbody filament, here a sphere.
To illustrate the validity of our approach, we have employed an ideal system that has a spherical blackbody filament enclosed by the filter: see Figure 2(a). The maximum luminous efficacy reaches 125lm/W. The details of the calculation were reported recently.4 For general purpose illumination, not only the efficiency but also the color quality is important in evaluating a bulb. The color quality of a bulb is commonly characterized by the correlated color temperature (CCT), used to categorize color tone, and the color rendering index (CRI), which measures the ability of a bulb to reproduce the true color of objects. If the CCT is lower than 3300K the color is categorized as a warm tone, whereas if the CCT is higher than 5300K the color is categorized as a cool tone. The CCT of our incandescent bulb did not exceed 3500K, indicating the filtered light is in the desired warm range. The CRI has a range between 0 and 100, with 0 being the minimum and 100 being the maximum color rendering capability. The color rendering index of our new light bulb is calculated to be between 68 and 90, better than that of a standard fluorescent lamp with a CRI of approximately 60.
Photon recycling via a metallic PBG filter is a promising new route to creating a ‘cool’ light bulb. Our next step is to study a cylindrical filter geometry that is comparable to the commonly used tungsten-filament configuration.
We would like to acknowledge the financial support of DOE-BES under grant number DE-FG02-06ER46347
------------------------
About Writer
Shawn-Yu Lin, Yong-Sung Kim
Physics
Rensselaer Polytechnic Institute
Troy, NY
Shawn-Yu Lin is an institute constellation professor and professor of physics at Rensselaer Polytechnic Institute. His expertise is in the interaction of light with hierarchy nanostructure. He is a fellow of the American Physical Society, a fellow of the Optical Society of America, and a distinguished member-of-technical-staff at Sandia National Laboratories
Yong Sung Kim specializes in electromagnetic wave modeling of three-dimensional photonic crystal structures including finite difference time domain, dispersion calculation and transfer matrix methods.
-------------------------------------------
References:
1. J. Brett, R. Fontana, P. Walsh, S. Spura, L. Parascandola, Development of high energy-conserving incandescent lamps, J., J. Illuminating Eng. Soc. 214, pp. 93, 1980.
2. R. Fontanta, I. Goldstein, L. Thorington, R. Howson, The design, construction and performance of an incandescent light source with a transparent heat mirror, Lighting Tech. 18, pp. 93, 1986.
3. R. Bergman, T. Parham, Application of thin film reflecting coating technology to tungsten filament lamps, IEE Proceedings-A 140, pp. 418, 1993.
4. Y. S. Kim, S. Y. Lin, A. Chang, J. H. Lee, K. M. Ho, Analysis of photon recycling using metallic photonic crystal, J. Appl. Phys. 102, pp. 063107, 2007.doi:10.1063/1.2779271
2008年7月27日 星期日
Self-Assembling Crystals Could Produce Better Optical Materials
Posted on: Friday, 27 June 2008, 06:02 CDT
By Shelley, Suzanne
MATERIALS Chemical engineers have developed a "self-assembling" method that could allow optical devices to be made less expensively than conventional processes, which require complex etching and other techniques common in the semiconductor industry.
The method, developed at Purdue Univ., works by positioning tiny particles onto a silicon template containing precisely spaced holes that are about one one-hundredth the width of a human hair. To produce the singlelayer structure, the engineers used Langmuir- Blodgett monolayer deposition, a standard technique used in physical chemistry, primarily to create lipid membranes for research.
The template is immersed in water in a trough-like vessel where a layer of particles has formed at the surface. As the template is pulled vertically out of the trough, the partides are pushed into the template holes by capillary force, the same phenomenon that causes water to rise to a higher level in a tube placed in a pool of water. It is critical for the particles to be spaced properly prior to the Langmuir-Blodgett deposition so that water can draw the particles into the holes in the template using capillary force, explains You-Yeon Won, an assistant professor of chemical engineering.
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The researchers have used the technique to create a "nearly perfect two-dimensional colloidal crystal," or a precisely ordered layer of particles, which is a critical step toward growing three- dimensional crystals for use in optical technologies.
"Making the first layer is very difficult, so we have taken an important step in the right direction," Won says. "Creating three- dimensional structures poses a big challenge, but I think it's feasible."
The single-layer structures might be used to form micro lenses to improve the performance of optical equipment, such as cameras and scientific instruments, or to control the color and other optical properties of materials for consumer products. More importantly, the technique could be used to create "omni-directional photonic band- gap materials," which would dramatically improve the performance of optical fibers, the researchers say. Omni-directional coatings would increase the amount of light transmitted by fiber-optics, and could possibly be used in future sensor technology and in optical computers and circuits that use light instead of electronic signals to process information.
The Purdue engineers are now investigating the creation of three- dimensional crystals from the two-dimensional structures. Currently, omni-directional materials are prohibitively expensive to manufacture.
A scanning electron microscopy photo shows a side-by-side comparison between Purdue's structure (right) and a structure that results when a template is not used. Photo courtesy of Y. Won and J. Hur.
Copyright American Institute of Chemical Engineers Jun 2008
(c) 2008 Chemical Engineering Progress. Provided by ProQuest Information and Learning. All rights Reserved.
Source: Chemical Engineering Progress
By Shelley, Suzanne
MATERIALS Chemical engineers have developed a "self-assembling" method that could allow optical devices to be made less expensively than conventional processes, which require complex etching and other techniques common in the semiconductor industry.
The method, developed at Purdue Univ., works by positioning tiny particles onto a silicon template containing precisely spaced holes that are about one one-hundredth the width of a human hair. To produce the singlelayer structure, the engineers used Langmuir- Blodgett monolayer deposition, a standard technique used in physical chemistry, primarily to create lipid membranes for research.
The template is immersed in water in a trough-like vessel where a layer of particles has formed at the surface. As the template is pulled vertically out of the trough, the partides are pushed into the template holes by capillary force, the same phenomenon that causes water to rise to a higher level in a tube placed in a pool of water. It is critical for the particles to be spaced properly prior to the Langmuir-Blodgett deposition so that water can draw the particles into the holes in the template using capillary force, explains You-Yeon Won, an assistant professor of chemical engineering.
GA_googleFillSlotWithSize("ca-pub-5440138744487553", "News_Main_300x250", 300, 250);
The researchers have used the technique to create a "nearly perfect two-dimensional colloidal crystal," or a precisely ordered layer of particles, which is a critical step toward growing three- dimensional crystals for use in optical technologies.
"Making the first layer is very difficult, so we have taken an important step in the right direction," Won says. "Creating three- dimensional structures poses a big challenge, but I think it's feasible."
The single-layer structures might be used to form micro lenses to improve the performance of optical equipment, such as cameras and scientific instruments, or to control the color and other optical properties of materials for consumer products. More importantly, the technique could be used to create "omni-directional photonic band- gap materials," which would dramatically improve the performance of optical fibers, the researchers say. Omni-directional coatings would increase the amount of light transmitted by fiber-optics, and could possibly be used in future sensor technology and in optical computers and circuits that use light instead of electronic signals to process information.
The Purdue engineers are now investigating the creation of three- dimensional crystals from the two-dimensional structures. Currently, omni-directional materials are prohibitively expensive to manufacture.
A scanning electron microscopy photo shows a side-by-side comparison between Purdue's structure (right) and a structure that results when a template is not used. Photo courtesy of Y. Won and J. Hur.
Copyright American Institute of Chemical Engineers Jun 2008
(c) 2008 Chemical Engineering Progress. Provided by ProQuest Information and Learning. All rights Reserved.
Source: Chemical Engineering Progress
2008年7月24日 星期四
美股評論：太陽能行業的烏雲
簡評：
這篇評論十分衷懇，值得細讀
－－－－－－－－－－－－－－－－－－－－－
【SmartMoney紐約7月22日訊】2008-07-22 14:12:53
Eric J. Savitz
太陽能股遭遇兩難困境。因為各種原因，太陽能正在成為熱門行業。陽光是免費的而且幾乎取之不盡；它不會產生溫室氣體；太陽能領域也沒有查韋斯和內賈德這樣的人物。樂觀人士預測，未來10到15年，美國用電的10%將來自太陽能。我們還可以想得更遠，去年《科學美國人》發表了一項計劃，美國可以在2050年之前從太陽能獲得69%的電能。
但是投資者管不了2050年那麼遠，他們所擔心的是下一個季度，眼光更長遠的也只看到2009年。就近期來講，太陽能板塊處境複雜，既有對一些關鍵市場中政府補貼看法的改變，也有即將面臨的多晶硅價格的下跌。如果你著眼長遠而且投資得當，你有可能掙大錢。但是整個過程中，情況會是複雜多變的。
2005年我們《巴倫週刊》就曾對太陽能板塊作出了分析，今天該行業顯然形勢更為嚴峻。我們當時分析的一些股票如今已經翻了三倍。如今再出現這樣的上漲可能要難一些，但是太陽能股依然潛力巨大。
利用陽光發電的想法已經產生有一個世紀了，20世紀50年代貝爾實驗室開始開發太陽能電池板。然而真正將太陽能當成化石燃料有力的競爭者，不過是近幾年的事。目前太陽能發電僅佔全球用電的1%。吸引力就在這裡：這是一個將近1萬億美元的未開發市場。Collins Stewart太陽能分析師丹-賴斯(Dan Ries)表示：“我們投資太陽能的根本原因是，如果價格能夠降下來，需求將達到驚人的高度。如果太陽能發電的成本能夠低於替代燃料，需求將比現在的產能大100倍。”
大批綠色科技風險企業瞄準太陽能行業，根據Cleantech的數據，2007年有10多億美元投資於太陽能企業的創辦。資金還在源源不斷地流入，2008年上半年已經接近10多億美元。理由很簡單，如果靠煤炭、石油和天然氣運轉的經濟能夠轉向太陽能，好處是巨大的。
轉折點將發生在達到“光伏發電平價上網”(Grid Parity)之時，即太陽能發電成本與化石燃料等傳統形式發電成本持平。現在還未達到，不過快了。在一些電力成本較高的市場，太陽能已經能夠形成成本相對較低的替代(比如8月中旬的夏威夷考艾島或7月驕陽似火的南加州)。最樂觀的看法是2010年能夠達到這一轉折點，現實一點的看法是2012年。化石燃料價格的變化也會產生巨大影響，如果煤炭和天然氣價格上升，“光伏發電平價上網”就容易達到一些。但是別忘了，太陽能不可能完全替代化石燃料，你不可能在晚上產生太陽能，而現在並無太好的儲存白天過剩能量的辦法。
太陽能行業已經在快速擴張，預計今年全球光電裝置將增長45%，達到39億瓦特，2012年到達151億瓦特。是什麼在推動這一增長？在未達到平價上網之前，仍是靠老式的政府施捨。
全球兩個最大的太陽能市場是德國和西班牙，它們加起來佔全球太陽能裝置的66%。兩個國家都實行有利的“強制光伏上網電價”(feed-in tariff)政策。德國擁有全球最大的一些太陽能電池板公司，這得感謝德國納稅人的慷慨。
全球變暖和減少對石油進口的依賴是開發太陽能很好的理由，但是靠納稅人來支持就使得這一行業在出現政治變動的時候十分脆弱。事實上，兩個主要市場的太陽能行業現在正面臨這樣的問題。
第一個就是美國，原來對太陽能裝置30%的投資稅收抵免政策今年年底到期，國會今年多次試圖進行展期都未能通過。現在行業普遍認為會有新的政策出台，但不會早於新總統就任之前。於此同時，美國的太陽能設施安裝有可能會陷於停頓。
另一個出問題的地方是西班牙，政府打算削減成本高昂的補貼額度。由於行業發展過快，給財政造成壓力，西班牙將大幅降低太陽能系統擁有者將電力出售給電網的速度，同時對新增裝置實施嚴格總量控制。
西班牙可能對太陽能補貼嚴格設限的威脅使得太陽能股大幅下挫，很多從6月初以來已經下降了20%多。上周，太陽能股再次大漲，原因是有報告稱西班牙將把補貼下限設在3億瓦特的裝置，遠遠低於原來提出的10億瓦特。美國很多州同樣在謀劃削減補貼。
美林分析師馬克-赫勒(Mark Heller)在最近一份報告中警告說，太陽能狂熱有可能失控，2007年和2008年太陽能創業公司籌集的資金均超過1998年互聯網公司的投入。赫勒警告道：“現在存在一種風險，這些公司可能對太陽能的長期前景過於樂觀，而未能考慮中期可能存在的風險，即大量政府補貼未能刺激起對太陽能的需求、同時缺乏成本競爭力。”
為什麼補貼如此重要？因為太陽能電池、模塊和系統的定價依然居高不下。這部分反映了西班牙等高補貼市場人為導致的高需求，同時也因為多晶硅長期緊缺。同樣用來生產電子電路的聚乙烯價格驚人。最近幾個月聚乙烯的現價高達每公斤450美元，而數年前還不到100美元。其實每公斤250美元，聚乙烯生產就已經是暴利了，真正的生產成本可能只有30美元/公斤。
這就使得MEMC Electronic Materials(WFR)和Wacker Chemie等聚乙烯生產商大賺特賺，並吸引了大量新的產商進來，比如韓國的DC Chemical，這家公司股價過去一年漲了三倍有餘。
既然多晶硅在太陽能電池的定價中是主導因素，聚乙烯的大量供應將使得電池板、模塊和系統的生產成本下降。事實上，2012年的合同價格已經遠遠低於2008年的價格了。
這對太陽能公司不見得是好事。到2009年，太陽能行業電池板的產能是90億瓦特，但是最樂觀的情況下需求也不會大幅超過65億瓦特。價格可能會大幅下跌。
價格下跌之後，行業的經濟學將發生改變。長期來看，補貼會消失。電池板製造商會改良設計來提高太陽能利用率，這最終會成為一個商品行業。華爾街已經弄清楚了，儘管太陽能設備增長率很高，它們只能享有中等的市盈率，更接近希捷或美光，而非谷歌和蘋果。
這篇評論十分衷懇，值得細讀
－－－－－－－－－－－－－－－－－－－－－
【SmartMoney紐約7月22日訊】2008-07-22 14:12:53
Eric J. Savitz
太陽能股遭遇兩難困境。因為各種原因，太陽能正在成為熱門行業。陽光是免費的而且幾乎取之不盡；它不會產生溫室氣體；太陽能領域也沒有查韋斯和內賈德這樣的人物。樂觀人士預測，未來10到15年，美國用電的10%將來自太陽能。我們還可以想得更遠，去年《科學美國人》發表了一項計劃，美國可以在2050年之前從太陽能獲得69%的電能。
但是投資者管不了2050年那麼遠，他們所擔心的是下一個季度，眼光更長遠的也只看到2009年。就近期來講，太陽能板塊處境複雜，既有對一些關鍵市場中政府補貼看法的改變，也有即將面臨的多晶硅價格的下跌。如果你著眼長遠而且投資得當，你有可能掙大錢。但是整個過程中，情況會是複雜多變的。
2005年我們《巴倫週刊》就曾對太陽能板塊作出了分析，今天該行業顯然形勢更為嚴峻。我們當時分析的一些股票如今已經翻了三倍。如今再出現這樣的上漲可能要難一些，但是太陽能股依然潛力巨大。
利用陽光發電的想法已經產生有一個世紀了，20世紀50年代貝爾實驗室開始開發太陽能電池板。然而真正將太陽能當成化石燃料有力的競爭者，不過是近幾年的事。目前太陽能發電僅佔全球用電的1%。吸引力就在這裡：這是一個將近1萬億美元的未開發市場。Collins Stewart太陽能分析師丹-賴斯(Dan Ries)表示：“我們投資太陽能的根本原因是，如果價格能夠降下來，需求將達到驚人的高度。如果太陽能發電的成本能夠低於替代燃料，需求將比現在的產能大100倍。”
大批綠色科技風險企業瞄準太陽能行業，根據Cleantech的數據，2007年有10多億美元投資於太陽能企業的創辦。資金還在源源不斷地流入，2008年上半年已經接近10多億美元。理由很簡單，如果靠煤炭、石油和天然氣運轉的經濟能夠轉向太陽能，好處是巨大的。
轉折點將發生在達到“光伏發電平價上網”(Grid Parity)之時，即太陽能發電成本與化石燃料等傳統形式發電成本持平。現在還未達到，不過快了。在一些電力成本較高的市場，太陽能已經能夠形成成本相對較低的替代(比如8月中旬的夏威夷考艾島或7月驕陽似火的南加州)。最樂觀的看法是2010年能夠達到這一轉折點，現實一點的看法是2012年。化石燃料價格的變化也會產生巨大影響，如果煤炭和天然氣價格上升，“光伏發電平價上網”就容易達到一些。但是別忘了，太陽能不可能完全替代化石燃料，你不可能在晚上產生太陽能，而現在並無太好的儲存白天過剩能量的辦法。
太陽能行業已經在快速擴張，預計今年全球光電裝置將增長45%，達到39億瓦特，2012年到達151億瓦特。是什麼在推動這一增長？在未達到平價上網之前，仍是靠老式的政府施捨。
全球兩個最大的太陽能市場是德國和西班牙，它們加起來佔全球太陽能裝置的66%。兩個國家都實行有利的“強制光伏上網電價”(feed-in tariff)政策。德國擁有全球最大的一些太陽能電池板公司，這得感謝德國納稅人的慷慨。
全球變暖和減少對石油進口的依賴是開發太陽能很好的理由，但是靠納稅人來支持就使得這一行業在出現政治變動的時候十分脆弱。事實上，兩個主要市場的太陽能行業現在正面臨這樣的問題。
第一個就是美國，原來對太陽能裝置30%的投資稅收抵免政策今年年底到期，國會今年多次試圖進行展期都未能通過。現在行業普遍認為會有新的政策出台，但不會早於新總統就任之前。於此同時，美國的太陽能設施安裝有可能會陷於停頓。
另一個出問題的地方是西班牙，政府打算削減成本高昂的補貼額度。由於行業發展過快，給財政造成壓力，西班牙將大幅降低太陽能系統擁有者將電力出售給電網的速度，同時對新增裝置實施嚴格總量控制。
西班牙可能對太陽能補貼嚴格設限的威脅使得太陽能股大幅下挫，很多從6月初以來已經下降了20%多。上周，太陽能股再次大漲，原因是有報告稱西班牙將把補貼下限設在3億瓦特的裝置，遠遠低於原來提出的10億瓦特。美國很多州同樣在謀劃削減補貼。
美林分析師馬克-赫勒(Mark Heller)在最近一份報告中警告說，太陽能狂熱有可能失控，2007年和2008年太陽能創業公司籌集的資金均超過1998年互聯網公司的投入。赫勒警告道：“現在存在一種風險，這些公司可能對太陽能的長期前景過於樂觀，而未能考慮中期可能存在的風險，即大量政府補貼未能刺激起對太陽能的需求、同時缺乏成本競爭力。”
為什麼補貼如此重要？因為太陽能電池、模塊和系統的定價依然居高不下。這部分反映了西班牙等高補貼市場人為導致的高需求，同時也因為多晶硅長期緊缺。同樣用來生產電子電路的聚乙烯價格驚人。最近幾個月聚乙烯的現價高達每公斤450美元，而數年前還不到100美元。其實每公斤250美元，聚乙烯生產就已經是暴利了，真正的生產成本可能只有30美元/公斤。
這就使得MEMC Electronic Materials(WFR)和Wacker Chemie等聚乙烯生產商大賺特賺，並吸引了大量新的產商進來，比如韓國的DC Chemical，這家公司股價過去一年漲了三倍有餘。
既然多晶硅在太陽能電池的定價中是主導因素，聚乙烯的大量供應將使得電池板、模塊和系統的生產成本下降。事實上，2012年的合同價格已經遠遠低於2008年的價格了。
這對太陽能公司不見得是好事。到2009年，太陽能行業電池板的產能是90億瓦特，但是最樂觀的情況下需求也不會大幅超過65億瓦特。價格可能會大幅下跌。
價格下跌之後，行業的經濟學將發生改變。長期來看，補貼會消失。電池板製造商會改良設計來提高太陽能利用率，這最終會成為一個商品行業。華爾街已經弄清楚了，儘管太陽能設備增長率很高，它們只能享有中等的市盈率，更接近希捷或美光，而非谷歌和蘋果。
2008年7月15日 星期二
新式塗料太陽能板技術提升50%能效
(R. Colin Johnson)
透過一種將有機染料塗在窗戶上，而使得新建置的太陽能板幾乎無法用肉眼察覺的「塗料太陽能板」(Paint-on solar panels)技術，據稱可望提升50%的太陽能轉換效率。
塗料太陽能板的開發者表示，由於所吸收的光線可傳至太陽能板邊緣轉換成能源，因而我們只需在太陽能板邊緣加裝主動式太陽能電池，即可降低成本。
根據美國麻省理工學院(Massachusetts Institute of Technology，MIT)的工程教授Marc Baldoat表示，太陽能收集器通常需要以鏡片或透光來追蹤太陽的位置，接著將焦點產生的熱散去。Baldoat所開發的有機染料塗層製程不需使用鏡片即可吸收光線，不會有由焦點產生熱的問題，也不需要加裝任何外部零件。
透過該項製程的太陽能板可將光源集中達40倍，而架設於邊緣的太陽能電池即可將太陽能轉換成電能。
該染料透過一塊玻璃表面吸收具有特定波長的光源，接著透過太陽能板，以不同波長將太陽能傳輸到位於邊緣的太陽能電池。由於主動式太陽能電池只需要被安裝在太陽能板邊緣，因此它們的價格將比傳統的太陽能板便宜，Baldo表示。
過去業界也曾使用過高分子塗料在太陽能板表面傳輸光線，然而MIT的技術是首次在玻璃表面塗上塗料的製程技術。具有不同染料塗層的應用使研究人員得以控制可被吸收的光波長，以及最小化太陽能傳輸到邊緣電池時的能量損耗。
塗料太陽能板的開發計畫是由MIT電子實驗室博士後研究人員Shalom Goffri以及Michael Currie、Jon Mapel和Timothy Heidel博士候選人共同參與，並由美國國家科學基金會(National Science Foundation)、MIT電子實驗室、微系統技術實驗室(Microsystems Technology Laboratories)以及軍事奈米技術研究所(Institute for Soldier Nanotechnologies)共同贊助。
<原文>
Paint-on solar panels could cut cost, boost efficiency
R. Colin Johnson EE Times (07/10/2008 2:00 H EDT)
PORTLAND, Ore. — Paint-on solar panels could boost current energy efficiency by 50 percent while making new solar panel installations virtually invisible by painting organic dyes onto windows.
By absorbing light and transporting energy to panel edges, developers of the paint-on solar panels said they could lower cost by only requiring active solar cells around a panel edges.
Solar concentrators usually have to track the sun with mirrors or light troughs, then dissipate heat building up at their focal points, according to Marc Baldoat, an engineering professor at the Massachusetts Institute of technology. His organic-dye coating process absorbs the light without mirrors, has no focal point to heat up and requires no moving parts.
Edge-mounted solar cells, where light is concentrated by as much as 40 times, then convert the energy to electricity.
The dyes absorb light across a glass panels surface in a range of wavelengths, then transport energy across the panel and re-emit it at a different wavelength in solar cells at the edges. Since active solar cells need only be mounted around the edge of these panels, they will be cheaper than traditional solar panels, Baldo claimed.
Shalom Goffri, a postdoctoral associate in MIT's Research Laboratory of Electronics also contributed to the work, along with doctoral candidates Michael Currie, Jon Mapel and Timothy Heidel.
Using dyes to transport light across a solar panel's surface has been tried before using polymers, according to the researchers. The MIT technique represents the first time it has been applied to glass. The application of several coats of different dyes allowed the researchers to control which wavelengths are absorbed, as well as minimize losses as energy is transported to the edge-mounted solar cells.
Funding for development of the paint-on solar panels was provided by the National Science Foundation, MIT's Research Laboratory of Electronics, Microsystems Technology Laboratories and the Institute for Soldier Nanotechnologies.
透過一種將有機染料塗在窗戶上，而使得新建置的太陽能板幾乎無法用肉眼察覺的「塗料太陽能板」(Paint-on solar panels)技術，據稱可望提升50%的太陽能轉換效率。
塗料太陽能板的開發者表示，由於所吸收的光線可傳至太陽能板邊緣轉換成能源，因而我們只需在太陽能板邊緣加裝主動式太陽能電池，即可降低成本。
根據美國麻省理工學院(Massachusetts Institute of Technology，MIT)的工程教授Marc Baldoat表示，太陽能收集器通常需要以鏡片或透光來追蹤太陽的位置，接著將焦點產生的熱散去。Baldoat所開發的有機染料塗層製程不需使用鏡片即可吸收光線，不會有由焦點產生熱的問題，也不需要加裝任何外部零件。
透過該項製程的太陽能板可將光源集中達40倍，而架設於邊緣的太陽能電池即可將太陽能轉換成電能。
該染料透過一塊玻璃表面吸收具有特定波長的光源，接著透過太陽能板，以不同波長將太陽能傳輸到位於邊緣的太陽能電池。由於主動式太陽能電池只需要被安裝在太陽能板邊緣，因此它們的價格將比傳統的太陽能板便宜，Baldo表示。
過去業界也曾使用過高分子塗料在太陽能板表面傳輸光線，然而MIT的技術是首次在玻璃表面塗上塗料的製程技術。具有不同染料塗層的應用使研究人員得以控制可被吸收的光波長，以及最小化太陽能傳輸到邊緣電池時的能量損耗。
塗料太陽能板的開發計畫是由MIT電子實驗室博士後研究人員Shalom Goffri以及Michael Currie、Jon Mapel和Timothy Heidel博士候選人共同參與，並由美國國家科學基金會(National Science Foundation)、MIT電子實驗室、微系統技術實驗室(Microsystems Technology Laboratories)以及軍事奈米技術研究所(Institute for Soldier Nanotechnologies)共同贊助。
<原文>
Paint-on solar panels could cut cost, boost efficiency
R. Colin Johnson EE Times (07/10/2008 2:00 H EDT)
PORTLAND, Ore. — Paint-on solar panels could boost current energy efficiency by 50 percent while making new solar panel installations virtually invisible by painting organic dyes onto windows.
By absorbing light and transporting energy to panel edges, developers of the paint-on solar panels said they could lower cost by only requiring active solar cells around a panel edges.
Solar concentrators usually have to track the sun with mirrors or light troughs, then dissipate heat building up at their focal points, according to Marc Baldoat, an engineering professor at the Massachusetts Institute of technology. His organic-dye coating process absorbs the light without mirrors, has no focal point to heat up and requires no moving parts.
Edge-mounted solar cells, where light is concentrated by as much as 40 times, then convert the energy to electricity.
The dyes absorb light across a glass panels surface in a range of wavelengths, then transport energy across the panel and re-emit it at a different wavelength in solar cells at the edges. Since active solar cells need only be mounted around the edge of these panels, they will be cheaper than traditional solar panels, Baldo claimed.
Shalom Goffri, a postdoctoral associate in MIT's Research Laboratory of Electronics also contributed to the work, along with doctoral candidates Michael Currie, Jon Mapel and Timothy Heidel.
Using dyes to transport light across a solar panel's surface has been tried before using polymers, according to the researchers. The MIT technique represents the first time it has been applied to glass. The application of several coats of different dyes allowed the researchers to control which wavelengths are absorbed, as well as minimize losses as energy is transported to the edge-mounted solar cells.
Funding for development of the paint-on solar panels was provided by the National Science Foundation, MIT's Research Laboratory of Electronics, Microsystems Technology Laboratories and the Institute for Soldier Nanotechnologies.
2008年7月6日 星期日
Shell打造全球最大太陽能面板廠
簡評：
許久沒補新文章上來，一來因為日常工作繁忙，實在無心照顧這裡；二來也是因為新聞大多大同小異，沒什麼參考價值
這份新聞不一樣，他傳達一個新的訊息，即大廠方向－－大廠已經對下一波開始佈局
下一波太陽能市場，矽缺料該是無法避免的現象，這也造就了連台塑這樣保守穩健的大廠也投資8 Billium資金打造矽甲烷(Silane)廠
發展替代Si晶片太陽電池的三代太陽電池技術也是大廠虎視眈眈的目標，所謂三代電池有DSSC(SONY目標)，有CIGS(昭和Shell)，有多接面聚光型太陽電池(一般LED磊晶廠)，有thin-film Si太陽電池(富陽光電聯相光電)等等
DSSC受限於壽命及轉換率問題，五年內難以有量產的機會；多接面聚光太陽電池直接有成本過於昂貴的考驗；thin-film Si目前的轉換效率還過低，但相對地比前兩種有機會；CIGS是長久以來討論的目標--本來，CIGS生產容易，材料相對便宜，最有可能成為下一代太陽電池主流技術，但發展至今，CIGS的機會日漸渺茫，理由主要在其中所用的銦材質(Indium)，不但是導電玻璃(ITO)主要素材，也是LED的重要材料，在Touch Panel產業越形擴張，在LED照明市場即將大開的前提下，In勢必成為接下來大為缺料的原料；更況In本來就是較為稀有的金屬，提煉殊為不易
Anyway，市場的選擇终歸會向便宜以及易取得的方向發展！
--------------------------------
蔡韋羽/黃女瑛
昭和Shell石油公司計劃在2011年投入超過1,000億日圓(約9.3億美元)，建造全球規模最大的太陽能面板廠，預估年產能可達1,000百萬瓦(MWp)，相當於1座核能廠發電量。日本經濟新聞報導指出，有鑑於日本官方提出對家庭裝設太陽能面板補助計畫，將帶動市場需求，Shell看好太陽能面板設廠計畫，將可望使該公司除石油外，多出另1個新的獲利來源。不過，該公司在消息批露後旋即否認此說法。Shell目前在宮崎縣1廠的太陽能面板廠，係採用銅、銦等金屬化合物製造，年產能為20MWp，預計2009年6月開始運作的宮崎2廠，年產能預估為60MWp。日本媒體指出，Shell預計投注1,000億日圓新設廠房，落腳地可能選在日本、歐洲、中東這3處當中的1處，該公司將在2009年決定設廠地點。
對此太陽能業者表示，Shell於2006年出售其傳統結晶矽太陽能電池產能給Solarworld，轉而投入薄膜太陽能領域，推估主要即是認為近2年結晶矽太陽能會深受多晶矽缺料之苦，進而押注較具長期發展契機的銅銦鎵硒(CIGS)薄膜太陽能電池。以Shell身處傳統及再生能源供應者角度來看，應該是看好薄膜太陽能在太陽能發電市場最能與傳統電力抗衡的潛力，因此，才會大力發展CIGS薄膜太陽能。太陽能業者指出，目前CIGS轉換效率可區分為5吋以下小尺寸面板約18~19%，5吋以上大尺寸面板轉換效率約10%以上，日本CIGS主要生產廠除Shell，還有Honda，而國際知名CIGS廠則以Nonosolar為主，其於6月時亦宣布計劃將年產能規劃到1,000MWp。由於看好其轉換效率發展空間大，包括台灣數家太陽能業者亦於枱面下積極研發及投資，然CIGS產出良率挑戰性大，亦是多數有興趣的業者不敢在短期內大力投入的主要原因。太陽能業者認為，CIGS最重要觀察點即是2009年佔整個太陽光電市場比重為多少，確實銷售量是否與產能同步增加，就可看出CIGS是否已成功商品化。
許久沒補新文章上來，一來因為日常工作繁忙，實在無心照顧這裡；二來也是因為新聞大多大同小異，沒什麼參考價值
這份新聞不一樣，他傳達一個新的訊息，即大廠方向－－大廠已經對下一波開始佈局
下一波太陽能市場，矽缺料該是無法避免的現象，這也造就了連台塑這樣保守穩健的大廠也投資8 Billium資金打造矽甲烷(Silane)廠
發展替代Si晶片太陽電池的三代太陽電池技術也是大廠虎視眈眈的目標，所謂三代電池有DSSC(SONY目標)，有CIGS(昭和Shell)，有多接面聚光型太陽電池(一般LED磊晶廠)，有thin-film Si太陽電池(富陽光電聯相光電)等等
DSSC受限於壽命及轉換率問題，五年內難以有量產的機會；多接面聚光太陽電池直接有成本過於昂貴的考驗；thin-film Si目前的轉換效率還過低，但相對地比前兩種有機會；CIGS是長久以來討論的目標--本來，CIGS生產容易，材料相對便宜，最有可能成為下一代太陽電池主流技術，但發展至今，CIGS的機會日漸渺茫，理由主要在其中所用的銦材質(Indium)，不但是導電玻璃(ITO)主要素材，也是LED的重要材料，在Touch Panel產業越形擴張，在LED照明市場即將大開的前提下，In勢必成為接下來大為缺料的原料；更況In本來就是較為稀有的金屬，提煉殊為不易
Anyway，市場的選擇终歸會向便宜以及易取得的方向發展！
--------------------------------
蔡韋羽/黃女瑛
昭和Shell石油公司計劃在2011年投入超過1,000億日圓(約9.3億美元)，建造全球規模最大的太陽能面板廠，預估年產能可達1,000百萬瓦(MWp)，相當於1座核能廠發電量。日本經濟新聞報導指出，有鑑於日本官方提出對家庭裝設太陽能面板補助計畫，將帶動市場需求，Shell看好太陽能面板設廠計畫，將可望使該公司除石油外，多出另1個新的獲利來源。不過，該公司在消息批露後旋即否認此說法。Shell目前在宮崎縣1廠的太陽能面板廠，係採用銅、銦等金屬化合物製造，年產能為20MWp，預計2009年6月開始運作的宮崎2廠，年產能預估為60MWp。日本媒體指出，Shell預計投注1,000億日圓新設廠房，落腳地可能選在日本、歐洲、中東這3處當中的1處，該公司將在2009年決定設廠地點。
對此太陽能業者表示，Shell於2006年出售其傳統結晶矽太陽能電池產能給Solarworld，轉而投入薄膜太陽能領域，推估主要即是認為近2年結晶矽太陽能會深受多晶矽缺料之苦，進而押注較具長期發展契機的銅銦鎵硒(CIGS)薄膜太陽能電池。以Shell身處傳統及再生能源供應者角度來看，應該是看好薄膜太陽能在太陽能發電市場最能與傳統電力抗衡的潛力，因此，才會大力發展CIGS薄膜太陽能。太陽能業者指出，目前CIGS轉換效率可區分為5吋以下小尺寸面板約18~19%，5吋以上大尺寸面板轉換效率約10%以上，日本CIGS主要生產廠除Shell，還有Honda，而國際知名CIGS廠則以Nonosolar為主，其於6月時亦宣布計劃將年產能規劃到1,000MWp。由於看好其轉換效率發展空間大，包括台灣數家太陽能業者亦於枱面下積極研發及投資，然CIGS產出良率挑戰性大，亦是多數有興趣的業者不敢在短期內大力投入的主要原因。太陽能業者認為，CIGS最重要觀察點即是2009年佔整個太陽光電市場比重為多少，確實銷售量是否與產能同步增加，就可看出CIGS是否已成功商品化。
2008年6月15日 星期日
GaN LEDs Incorporate Laser Liftoff and Photonic Crystal
by Daniel S. Burgess
Applied Physics Letters, March 27, 2006, 133514.
The material of choice for solid-state lighting solutions from the ultraviolet to the blue-green region of the spectrum has been GaN. As with all LED materials, however, the relatively high refractive index of GaN tends to result in the trapping of light in the device structure by total internal refraction, and the sapphire typically used as a growth substrate for GaN presents further trapping and thermal management issues.
With an eye on improving the external efficiency of the devices, researchers fabricated GaN LEDs using laser liftoff and the addition of a 2-D photonic crystal region. Courtesy of Aurélien David.
A team of scientists at the University of California, Santa Barbara, and at Laboratoire Charles Fabry de l’Institut d’Optique in Orsay, France, has fabricated GaN LEDs that incorporate two approaches to improved light extraction: laser liftoff and photonic crystals. In laser liftoff, laser processing separates the LED structures from their growth substrate so they can be bonded to a different material with thermal, electrical and optical properties more conducive to device performance. It also is suited for use with thinning the structure to the microcavity regime, which results in the formation of resonant optical modes in the device so that interference effects cause most of the light to be emitted perpendicular to the output face. Photonic crystals in the form of two-dimensional periodic structures machined into the semiconductor stack act to diffract the guided light out of the device.
Aurélien David, a graduate researcher at both the university and the institute, characterized the work as seeking greater control of the performance of GaN LEDs. Light extraction in high-power emitters, he noted, generally is well-addressed with techniques that randomize the path of the light, such as the addition of a textured surface or the use of pyramid geometries, but these offer little control of the far-field emission pattern, which would benefit display and lighting applications. The photonic crystal LEDs, in contrast, promise to offer light-extraction efficiencies equivalent to those of the other methods but using a deterministic approach, enabling the tuning of the emission properties.
In the experiments, the scientists started with LEDs comprising InGaN quantum wells in GaN grown on sapphire. They coated the structure with gold to form what would become the lower mirror region and for flip-chip mounting onto AlN ceramic, and then removed the sapphire by liftoff using a 248-nm pulsed KrF laser.
Thinning of the newly exposed GaN buffer was performed by reactive ion-beam etching and chemical and mechanical polishing. Electron-beam lithography and another round of reactive ion-beam etching yielded a series of 250-nm-deep holes in the stack, forming a triangular-lattice photonic crystal with a lattice constant of 215 nm and a fill factor of 38 percent.
Accidental damage caused in the fabrication process resulted in a partial short and in otherwise poor electrical performance from the completed devices. Nevertheless, the investigators deduced by angle-resolved electroluminescence measurements and theoretical modeling that liftoff and thinned down LEDs incorporating a photonic crystal should display much higher external efficiencies than GaN-on-sapphire devices and offer control over the far-field pattern and directionality of emission.
Radiative loss to the lower mirror is a concern, but they suggest that material choice — such as substituting silver for the gold — and device design will mitigate this effect.
David noted that it remains an open question as to whether such advancements will make their way into commercial products, but he predicted that demonstration devices in two to three years could display comparable performance to that of contemporary high-power LEDs.
Aurélien David, a graduate researcher at both the university and the institute, characterized the work as seeking greater control of the performance of GaN LEDs. Light extraction in high-power emitters, he noted, generally is well-addressed with techniques that randomize the path of the light, such as the addition of a textured surface or the use of pyramid geometries, but these offer little control of the far-field emission pattern, which would benefit display and lighting applications. The photonic crystal LEDs, in contrast, promise to offer light-extraction efficiencies equivalent to those of the other methods but using a deterministic approach, enabling the tuning of the emission properties.
In the experiments, the scientists started with LEDs comprising InGaN quantum wells in GaN grown on sapphire. They coated the structure with gold to form what would become the lower mirror region and for flip-chip mounting onto AlN ceramic, and then removed the sapphire by liftoff using a 248-nm pulsed KrF laser.
Thinning of the newly exposed GaN buffer was performed by reactive ion-beam etching and chemical and mechanical polishing. Electron-beam lithography and another round of reactive ion-beam etching yielded a series of 250-nm-deep holes in the stack, forming a triangular-lattice photonic crystal with a lattice constant of 215 nm and a fill factor of 38 percent.
Accidental damage caused in the fabrication process resulted in a partial short and in otherwise poor electrical performance from the completed devices. Nevertheless, the investigators deduced by angle-resolved electroluminescence measurements and theoretical modeling that liftoff and thinned down LEDs incorporating a photonic crystal should display much higher external efficiencies than GaN-on-sapphire devices and offer control over the far-field pattern and directionality of emission.
Radiative loss to the lower mirror is a concern, but they suggest that material choice — such as substituting silver for the gold — and device design will mitigate this effect.
David noted that it remains an open question as to whether such advancements will make their way into commercial products, but he predicted that demonstration devices in two to three years could display comparable performance to that of contemporary high-power LEDs.
Applied Physics Letters, March 27, 2006, 133514.
2008年6月6日 星期五
透過量子態量測 科學家發現冷卻晶片的新方法
在連續量測的過程中，科學家總是得想盡辦法不干涉量子態(quantum states)的連貫性；而近來以色列和德國的科學家展開合作打破了以上的規則。他們打算透過對量子態的量測來控制熱力學(thermodynamics，即溫度)和熱力學函數──熵(entropy)。
科學家們聲稱，在一個二能級量子系統(two-level quantum systems)中──就像那些用於描述量子位元(q-bits)的系統──可透過對量子系統的量測頻率來控制溫度和熵；並因此可望實現新一代的冷卻方案，以快速沉降(instant-settling)原子、分子和固態元件。
這些來自以色列魏茲曼科學研究所(Weizmann Institute)和德國波茨坦大學(Potsdam University)的科學家們聲稱，控制熱力學和熵的常數，是用於量測其量子態的頻率。透過採用這種方式可以在更短時間內實現冷卻和量子態淨化(purification)，速度較透過控制迴路(control loop)實現熱平衡、冷卻或回饋要快很多。
與德國波茨坦大學的研究員Mathias Nest共同展開研究的魏茲曼科學研究所教授Gershon Kurizki、博士後研究員Noam Erez和博士候選人Goren Gordon表示，進行量子量測是侵入性的，典型的量測不會干擾被量測中的系統，但若某個量子系統正進行某項特定量測，則該系統與其他特定系統的耦合(coupling)，會暫時受到此量測的影響。
這些科學家表示，量子力學的特性可用以做為一種新的晶片級冷卻和量子運算方法。工程師們通常根據冷卻晶片所需散熱器(heat sink)的尺寸來計算熱量損失。而研究人員稱，超快速的量測會加速或延緩熱效應，因而使之與散熱器的尺寸無關。透過調節光學溫度量測的速率，研究人員發現溫度本身也是可以被調節的。
研究人員稱，採用連續量測還可以改變系統熵或下降時間(relaxation time)──即下降到最低能量態的所需時間。透過調整系統熵，未來的量子電腦可更快地達到中間結果(intermediate results)的沉降，各個運算之間的復原(resetting)時間也將加速。
(參考原文：Measuring quantum states could yield new chip-cooling scheme)
(R. Colin Johnson)
-----------------------------------------
原文
Measuring quantum states could yield new chip-cooling scheme
R. Colin JohnsonEE Times (06/03/2008 10:03 H EDT)
PORTLAND, Ore. — Scientists take great pains not to disturb the coherence of quantum states through constant measurements. Israeli and German scientists recently collaborated to turn this technique on its head, using the measurement of quantum states to control thermodynamics (temperature) and entropy (settling).
The scientists claim that in two-level quantum systems--like those used to represent quantum bits (q-bits)--the frequency used to measure them controls both temperature and entropy. The approach could enable novel cooling schemes as well as instant-settling for atomic, molecular and solid-state devices.
The scientists at the Weizmann Institute (Rehovot, Israel) and Potsdam University in Germany claim that the constant that controls thermodynamics and entropy is the frequency used to measure their quantum states. Both cooling and state purification, they claim, can be made to occur much more quickly than the normal time typically needed to achieve thermal equilibrium, cooling or feedback around a control loop.
Quantum measurements are intrusive, according to professor Gershon Kurizki, postdoctoral fellow Noam Erez and doctoral candidate Goren Gordon at the Wiesmann Institute. They worked in cooperation with researcher Mathias Nest at Potsdam University.
Classical measurements do not interfere with the system being measured. When a specific measurement is made in a quantum system, however, the coupling to other specific systems is temporarily interrupted by the measurement.
This odd characteristic of quantum mechanics can be harnessed, according to these scientists, as a new method of chip-scale cooling and quantum computing. Engineers usually measure heat loss in terms of the size of the heat sink needed to cool a chip. But the researchers claim that ultra-fast measurements can speed up or slow down thermal effects independent of the size of the heat sink.
By adjusting the rate at which optical temperature measurements were made, the researchers found that the temperature itself could be adjusted.
Taking frequent measurements also changed the system entropy or relaxation time--the time needed to reach the lowest energy state. By adjusting system entropy, future quantum computers could tilt toward faster settling of intermediate results and faster resetting between calculations, the researchers said.
科學家們聲稱，在一個二能級量子系統(two-level quantum systems)中──就像那些用於描述量子位元(q-bits)的系統──可透過對量子系統的量測頻率來控制溫度和熵；並因此可望實現新一代的冷卻方案，以快速沉降(instant-settling)原子、分子和固態元件。
這些來自以色列魏茲曼科學研究所(Weizmann Institute)和德國波茨坦大學(Potsdam University)的科學家們聲稱，控制熱力學和熵的常數，是用於量測其量子態的頻率。透過採用這種方式可以在更短時間內實現冷卻和量子態淨化(purification)，速度較透過控制迴路(control loop)實現熱平衡、冷卻或回饋要快很多。
與德國波茨坦大學的研究員Mathias Nest共同展開研究的魏茲曼科學研究所教授Gershon Kurizki、博士後研究員Noam Erez和博士候選人Goren Gordon表示，進行量子量測是侵入性的，典型的量測不會干擾被量測中的系統，但若某個量子系統正進行某項特定量測，則該系統與其他特定系統的耦合(coupling)，會暫時受到此量測的影響。
這些科學家表示，量子力學的特性可用以做為一種新的晶片級冷卻和量子運算方法。工程師們通常根據冷卻晶片所需散熱器(heat sink)的尺寸來計算熱量損失。而研究人員稱，超快速的量測會加速或延緩熱效應，因而使之與散熱器的尺寸無關。透過調節光學溫度量測的速率，研究人員發現溫度本身也是可以被調節的。
研究人員稱，採用連續量測還可以改變系統熵或下降時間(relaxation time)──即下降到最低能量態的所需時間。透過調整系統熵，未來的量子電腦可更快地達到中間結果(intermediate results)的沉降，各個運算之間的復原(resetting)時間也將加速。
(參考原文：Measuring quantum states could yield new chip-cooling scheme)
(R. Colin Johnson)
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原文
Measuring quantum states could yield new chip-cooling scheme
R. Colin JohnsonEE Times (06/03/2008 10:03 H EDT)
PORTLAND, Ore. — Scientists take great pains not to disturb the coherence of quantum states through constant measurements. Israeli and German scientists recently collaborated to turn this technique on its head, using the measurement of quantum states to control thermodynamics (temperature) and entropy (settling).
The scientists claim that in two-level quantum systems--like those used to represent quantum bits (q-bits)--the frequency used to measure them controls both temperature and entropy. The approach could enable novel cooling schemes as well as instant-settling for atomic, molecular and solid-state devices.
The scientists at the Weizmann Institute (Rehovot, Israel) and Potsdam University in Germany claim that the constant that controls thermodynamics and entropy is the frequency used to measure their quantum states. Both cooling and state purification, they claim, can be made to occur much more quickly than the normal time typically needed to achieve thermal equilibrium, cooling or feedback around a control loop.
Quantum measurements are intrusive, according to professor Gershon Kurizki, postdoctoral fellow Noam Erez and doctoral candidate Goren Gordon at the Wiesmann Institute. They worked in cooperation with researcher Mathias Nest at Potsdam University.
Classical measurements do not interfere with the system being measured. When a specific measurement is made in a quantum system, however, the coupling to other specific systems is temporarily interrupted by the measurement.
This odd characteristic of quantum mechanics can be harnessed, according to these scientists, as a new method of chip-scale cooling and quantum computing. Engineers usually measure heat loss in terms of the size of the heat sink needed to cool a chip. But the researchers claim that ultra-fast measurements can speed up or slow down thermal effects independent of the size of the heat sink.
By adjusting the rate at which optical temperature measurements were made, the researchers found that the temperature itself could be adjusted.
Taking frequent measurements also changed the system entropy or relaxation time--the time needed to reach the lowest energy state. By adjusting system entropy, future quantum computers could tilt toward faster settling of intermediate results and faster resetting between calculations, the researchers said.
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