Use of tin oxide as an inexpensive antireflection coating for p on n polycrystalline silicon solar cells

The potential of tin oxide as an inexpensive antireflection (AR) coating for polycrystalline silicon solar cells has been investigated. Undoped tin oxide films of a desired thickness were deposited over p on n polycrystalline silicon solar cells by spray pyrolysis of an alcoholic solution of hydrated stannic chloride at 500°C. Evaluation of cell performance before and after this AR coating showed that the AR coating is highly compatible with the polycrystalline silicon solar cells. About 40-50 percent improvement in the short-circuit current of p on n polycrystalline cells has been measured. The coating may be highly suited to large-scale production of low-cost polycrystalline silicon solar cells for terrestrial application.     

Performance enhancement of multicrystalline silicon solar cells and modules using double‐layered SiNx:H antireflection coatings

Silicon nitride coating deposited by the plasma‐enhanced chemical vapor deposition method is the most widely used antireflection coating for crystalline silicon solar cells. In this work, we employed double‐layered silicon nitride coating consisting of a top layer with a lower refractive index and a bottom layer (contacting the silicon wafer) with a higher refractive index for multicrystalline silicon solar cells. An optimization procedure was presented for maximizing the photovoltaic performance of the encapsulated solar cells or modules. The dependence of their photovoltaic properties on the thickness of silicon nitride coatings was carefully analyzed. Desirable thicknesses of the individual silicon nitride layers for the double‐layered coatings were calculated. In order to get statistical conclusions, we fabricated a large number of multicrystalline silicon solar cells using the standard production line for both the double‐layered and single‐layered antireflection coating types. On the cell level, the double‐layered silicon nitride antireflection coating resulted in an increase of 0.21%, absolute for the average conversion efficiency, and 1.8 mV and 0.11 mA/cm² for the average open‐circuit voltage and short‐circuit current density, respectively. On the module level, the cell to module power transfer factor was analyzed, and it was demonstrated that the double‐layered silicon nitride antireflection coating provided a consistent enhancement in the photovoltaic performance for multicrystalline silicon solar cell modules than the single‐layered silicon nitride coating. Copyright © 2015 John Wiley & Sons, Ltd.     

Spectral and photoelectric parameters of high-voltage multi-junction solar batteries

The test samples of silicon high-voltage multi-junction solar batteries (SHVMJSB) are investigated experimentally. It is shown that the efficiency of the transformation of sunlight by silicon high-voltage multi-junction solar batteries without special antireflection coatings is not high and equal to 8%. It is due to the fact that the recombination rate of the minor charge carries is high on the damaged layer surface. The surface refinement and the antireflection coating make it possible to increase the efficiency of the transformation of sunlight by the silicon high-voltage multi-junction solar batteries of up to 13%.     

Optimization of moth‐eye antireflection schemes for silicon solar cells

Nanostructured moth‐eye antireflection schemes for silicon solar cells are simulated using rigorous coupled wave analysis and compared to traditional thin film coatings. The design of the moth‐eye arrays is optimized for application to a laboratory cell (air–silicon interface) and an encapsulated cell (EVA‐silicon interface), and the optimization accounts for the solar spectrum incident on the silicon interface in both cells, and the spectral response of both types of cell. The optimized moth‐eye designs are predicted to outperform an optimized double layer thin film coating by approximately 2% for the laboratory cell and approximately 3% for the encapsulated cell. The predicted performance of the silicon moth‐eye under encapsulation is particularly remarkable as it exhibits losses of only 0·6% compared to an ideal AR surface. Copyright © 2010 John Wiley & Sons, Ltd.     

Double-layered silicon nitride antireflection coatings for multicrystalline silicon solar cells

Silicon nitride coating possesses both optical antireflection and electrical passivation effects for crystalline silicon solar cells. In this work, we employed a double-layered silicon nitride coating consisting of a top layer with a lower refractive index and a bottom layer (contacting the silicon wafer) with a higher refractive index for multicrystalline silicon solar cells. Double-layered silicon nitride coating provides a lower optical reflection and better surface passivation than those of single-layered silicon nitride. Details for optimizing the double-layered silicon nitride coating are presented. In order to get statistical conclusions, we fabricated a large number of multicrystalline silicon solar cells using the production line for both the double-layered and single-layered cell types. It was statistically demonstrated that the double-layered silicon nitride coating provided a consistent enhancement in the photovoltaic performance of multicrystalline silicon solar cells over those of the single-layered silicon nitride coating.     

Double layer antireflection coating for high-efficiency passivatedemitter silicon solar cells

Recent high-efficiency silicon solar cells employ high-quality oxides both for surface passivation and as a rudimentary antireflection coating. This gives over 3% reflection at the cell front surface, even though the surface is microstructured. A double layer antireflection coating applied to cells with reduced SiO₂ thickness reduces the cell reflection. However, although reflection is minimized by reducing the oxide thickness to values below 100 Å, a rapid falloff in both open-circuit voltage and short-circuit current is observed experimentally once this thickness is reduced below 200 Å. The best compromise is found when oxide thickness is 250 Å which allows improved short-circuit current density without appreciable loss in open-circuit voltage     

Optimised antireflection coatings for planar silicon solar cells using remote PECVD silicon nitride and porous silicon dioxide

Silicon nitride (SiN) films fabricated by remote plasma‐enhanced chemical vapour deposition (RPECVD) have recently been shown to provide an excellent electronic passivation of silicon surfaces. This property, in combination with its large refractive index, makes RPECVD SiN an ideal candidate for a surface‐passivating antireflection coating on silicon solar cells. A major problem of these films, however, is the fact that the extinction coefficient increases with increasing refractive index. Hence, a careful optimisation of RPECVD SiN based antireflection coatings on silicon solar cells must consider the light absorption within the films. Optimal optical performance of silicon solar cells in air is obtained if the RPECVD SiN films are combined with a medium with a refractive index below 1·46, such as porous SiO₂. In this study, the dispersion of the refractive indices and the extinction coefficients of RPECVD SiN, porous SiO₂, and several other relevant materials (MgF₂, TiO_x, ZnS, B270 crown glass, soda lime glass, ethylene vinyl acetate and resin as used in commercial photovoltaic modules) are experimentally determined. Based on these data, the short‐circuit currents of planar silicon solar cells covered by RPECVD SiN and/or porous SiO₂ single‐ and multi‐layer antireflection coatings are numerically maximised for glass‐encapsulated as well as non‐encapsulated operating conditions. The porous SiO₂/RPECVD SiN‐based antireflection coatings optimised for these applications are shown to be universally suited for silicon solar cells, regardless of the internal blue or red response of the cells. Copyright © 1999 John Wiley & Sons, Ltd.     

Use of porous silicon antireflection coating in multicrystallinesilicon solar cell processing

The latest results on the use of porous silicon (PS) as an antireflection coating (ARC) in simplified processing for multicrystalline silicon solar cells are presented. The optimization of a PS selective emitter formation results in a 14.1% efficiency multicrystalline (5×5 cm²) Si cell with evaporated contacts processed without texturization, surface passivation, or additional ARC deposition. Specific attention is given to the implementation of a PS ARC into an industrially compatible screen-printed solar cell process. Both the chemical and electrochemical PS ARC formation method are used in different solar cell processes, as well as on different multicrystalline silicon materials. Efficiencies between 12.1 and 13.2% are achieved on large-area (up to 164 cm² ) commercial Si solar cells     

Emitter design for high-efficiency silicon solar cells. Part 2: Space cells

Over the last decade there have been substantial improvements in the performance of silicon solar cells. This second part of a two-part paper examines the implications for use in space. High-efficiency cells, including cells of above 20% Air Mass 0 efficiency were exposed to 1 MeV of electron irradiation. Although the relative performance loss was higher, the cells gave higher performance than conventional silicon space cells even after 5 × 10¹⁵ cm⁻² 1-MeV electron radiation damage. However, spectral response measurement shows that the rapid degradation mainly came from damage on the emitter surface. This can be accommodated simply by shallow emitter designs. the efficiency of an optimized silicon space cell is expected to be over 14% after 1 × 10¹⁵ cm⁻² 1 MeV electron radiation.     

Moth‐eye antireflection coating fabricated by nanoimprint lithography on 1 eV dilute nitride solar cell

We report on the performance of biomimicked antireflection coating applied to dilute nitride solar cell. The coating consists of nanostructures replicating the moth‐eye geometry and has been fabricated by nanoimprint lithography directly within the window layer covering the dilute nitride absorbing junction. The mean reflectivity within the spectral range of 320–1800 nm remains under 5% for incident angles up to 45°. The effect of the coating on the cell performance was assessed by measuring the current–voltage characteristics under simulated solar illumination. A clear performance increase was identified when comparing a solar cell with the moth‐eye coating with a solar cell having a standard SiN_x/SiO₂ coating. Copyright © 2012 John Wiley & Sons, Ltd.     

Silicon solar cells based on all‐laser‐transferred contacts

Crystalline silicon solar cells based on all‐laser‐transferred contacts (ALTC) have been fabricated with both front and rear metallization achieved through laser induced forward transferring. Both the front and rear contacts were laser‐transferred from a glass slide coated with a metal layer to the silicon substrate already processed with emitter formation, surface passivation, and antireflection coating. Ohmic contacts were achieved after this laser transferring. The ALTC solar cells were fabricated on chemically textured p‐type Cz silicon wafers. An initial conversion efficiency of over 15% was achieved on a simple cell structure with full‐area emitter. Further improvements are expected with optimized laser transferring conditions, front grid pattern design, and surface passivation. The ALTC process demonstrates the advantage of laser processing in simplifying the solar cell fabrication by a one‐step metal transferring and firing process. Copyright © 2013 John Wiley & Sons, Ltd.     

多晶硅太阳电池的氮化硅钝化

全面介绍了等离子增强化学汽相沉积 ( PECVD)纳米氮化硅 ( Si Nx∶ H)光电薄膜的技术发展及现状 ,分析了 PECVD法沉积的 Si Nx∶ H薄膜对多晶硅太阳电池的体钝化和表面钝化机理     

Antireflection coating design for series interconnected multi‐junction solar cells

Antireflection coating design for multi‐junction solar cells can be more challenging than in the single‐junction case. Reasons for this are discussed. Analytical expressions used to optimize antireflection (AR) coatings for single junction solar cells are extended for use in monolithic, series interconnected multi‐junction solar cell AR coating design. The result is an analytical expression which relates the solar cell performance (through J_sc) directly to the AR coating design through the device reflectance. It is also illustrated how AR coating design can be used to provide an additional degree of freedom for current matching multi‐junction devices. Published in 2000 by John Wiley & Sons, Ltd.     

Dielectric films for Si solar cell applications

Thin films of many dielectric materials have been used in the past for fabrication of solar cells and as a part of their device structure. However, current efforts to reduce solar cell costs in commercial production have led to simplification of cell design and fabrication. Use of self-aligning techniques has obviated the need for photolithography and conventional masking with dielectric films for cell fabrication. Currently, the most favored dielectric material in Si solar cell production is SiN:H, deposited by the plasma-enhanced chemical vapor deposition (PECVD) process. The SiN:H layer and its processing play multiple roles of serving as an antireflection coating, a surface passivating layer, a buffer layer through which metal is fired, and a means of transporting hydrogen into the bulk of the solar cell. In order to optimize the solar cell performance, the SiN:H layer must meet some conflicting demands. The various applications of the SiN:H layer in solar cell fabrication are described here.     

18-percent efficient terrestrial silicon solar cells

Silicon solar cells are described which operate at energy conversion efficiencies in excess of 18 percent under standard terrestrial test conditions (AM1.5, 100 mW/cm², 28°C). These are believed to be the most efficient silicon cells reported to date. The high efficiency is a result of the combination of high open-circuit voltage due to the careful attention paid to passivation of the top surface of the cell; high fill factors due to the high open-circuit voltage and low parasitic resistance losses; and high short-circuit current due to the use of shallow diffusions, a low grid coverage, and an optimized double-layer antireflection coating.     

多晶硅太阳电池PECVD氮化硅钝化工艺的研究

介绍等离子体化学气相淀积(PECVD)制备减反射钝化膜。将PECVD设备运用于太阳电池生产线上,发现通过PECVD设备可以对多晶硅太阳电池有很好的钝化效果。分析PECVD对多晶硅太阳电池钝化机理。     

单晶硅太阳电池纳米减反射膜的研究

报道了用热喷涂工艺制备单晶硅太阳电池纳米减反射膜的研究结果 ,讨论了衬底温度对 Ti Ox 纳米减反射膜结构及折射率的影响 ,优化了热喷涂的工艺条件 ,并研究了 Ti Ox 纳米减反射膜对单体太阳电池效率的贡献。实验证明 ,用热喷涂工艺制备的纳米 Ti Ox 减反射膜可使 1 0 0 mm× 1 0 0 mm单体太阳电池的平均光电转换效率增加 8%～ 9%。     

Light‐enhanced surface passivation of TiO2‐coated silicon

Titanium dioxide is shown to afford good passivation to non‐diffused silicon surfaces and boron‐diffused surfaces after a low‐temperature anneal. The passivation most likely owes to the significant levels of negative charge instilled in the films, and passivation is enhanced by illumination—advantageous for solar cells—indicating that a titanium dioxide photoreaction is at least partly responsible for the low surface recombination. We demonstrate a surface recombination velocity of less than 30 cm/s, on a 5‐Ω cm n‐type silicon, and an emitter saturation current density of 90 fA/cm² on a 200‐Ω/sq boron diffusion. If these titanium dioxide passivated boron‐diffused surfaces were employed in a crystalline silicon solar cell, an open‐circuit voltage as high as 685 mV could be achieved. Given that TiO₂ has a high refractive index and was deposited with atmospheric pressure chemical vapour deposition, an inexpensive technique, it has the potential as a passivating antireflection coating for industrial boron‐diffused silicon solar cells. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of post-PECVD photo-assisted anneal on multicrystallinesilicon solar cells

Silicon nitride (SiN_x) films deposited by plasma enhanced chemical vapor deposition (PECVD) contain large amount of atomic hydrogen which can be driven into bulk silicon by post-PECVD anneal. The objective of this paper is to understand and quantify the effects of the anneal on multicrystalline silicon (mc-Si) solar cells. Detailed cell analysis and model calculations are performed to assess the impact of the anneal on mc-Si cells. Simple n⁺-p-p⁺ solar cells with PECVD SiN_x/SiO₂ antireflection (AR) coating are annealed in the temperature range of 350°C to 700°C. The efficiency of the cells made on EFG silicon increases by 45% due to the AR coating and then additional 25% due to the anneal. A trade off between short and long wavelength response is found during the anneal. Low temperature anneal increases the short wavelength response, while high temperature anneal improves the long wavelength response at the expense of the short wavelength response. It is shown that the increase in short wavelength response is due to improved surface passivation, and the decrease in short wavelength response after high temperature anneals is the result of the increase in short wavelength absorption in the SiN_x film. Higher quality HEM silicon cells do not show appreciable increase in the long wavelength response at higher anneal temperatures. Thus post-PECVD low temperature anneal helps all mc-Si cells, but the effect of high temperature anneal is material specific. Cells made from materials which do not respond to hydrogenation can degrade at high temperature anneal     

Sunrise to sunset optimization of thin film antireflective coatings for encapsulated,planar silicon solar cells

We present an approach for the optimization of thin film antireflective coatings for encapsulated planar silicon solar cells in which the variations in the incident spectra and angle of incidence (AOI) over a typical day are fully considered. Both the angular and wavelength dependences of the reflectance from the surface, absorptance within the coating, and transmittance into the device are calculated for both single‐ and double‐layer antireflection coatings with and without thin silicon oxide passivation layers. These data are then combined with spectral data as a function of time of day and internal quantum efficiency to estimate the average short‐circuit current produced by a fixed solar cell during a day. This is then used as a figure of merit for the optimization of antireflective layer thicknesses for modules placed horizontally at the equator and on a roof in the UK. Our results indicate that only modest gains in average short‐circuit current could be obtained by optimizing structures for sunrise to sunset irradiance rather than AM1·5 at normal incidence, and fabrication tolerances and uniformities are likely to be more significant. However, we believe that this overall approach to optimization will be of increasing significance for new, potentially asymmetric, antireflection schemes such as those based on subwavelength texturing or other photonic or plasmonic technologies currently under development especially when considered in combination with modules fixed at locations and directions that result in asymmetric spectral conditions. Copyright © 2009 John Wiley & Sons, Ltd.