晶体硅太阳电池的应用及发展

随着全球气候变暖、污染问题日益严重,从传统能源向可再生能源的转变势在必行。其中太阳能作为可再生能源的重要部分,最近几年已经得到了很广泛的应用。晶体硅太阳能电池是目前多种太阳能电池中技术最为成熟、光电转换效率最高、应用最为广泛的一种,目前国外单晶硅太阳能电池实验室转换效率最高已达到24.7%,多晶硅太阳能电池达到19.8%。本文就晶体硅太阳电池的应用及发展做一简要介绍。     

硅烷偶联剂对太阳电池铝浆性能的影响及分析

在晶体硅太阳电池制造过程中,铝电极是通过丝网印刷-烘干-烧结制成的。该过程中铝电极膜层与传送网带发生相对摩擦,易导致铝膜表面产生划痕、起灰。重点研究了添加不同质量分数w(硅烷偶联剂)(0.5%~3.0%)对铝浆有机载体的表面张力、铝膜表面划痕、起灰、导电性能的影响规律。结果表明:当w(硅烷偶联剂)为2.5%时,有机载体的表面张力可从约30mN/m降低至25.69mN/m,提高了铝粉颗粒之间以及铝膜与硅片之间的黏附作用,从而减少划痕和灰化,进而可使铝电极的接触电阻由0.60?降低至0.19?。     

N型背发射极晶体硅太阳电池模拟研究

N型晶体太阳电池由于少子寿命高、光致衰减低、弱光响应好等优点,近年来在高效率低成本太阳电池领域一直备受关注。利用PC1D模拟,对N型背发射极晶体硅太阳电池进行了分析。结果表明,背发射极掺杂浓度、结深、背表面复合速率、前表面掺杂浓度及复合速率都对电池转换效率有较大影响,尤其是电池前表面与背表面复合速率对电池性能的影响最为明显,而电池前表面场掺杂深度则对电池性能影响较小。对于前表面复合来说,当前表面复合速率小于1×103cm/s时,电池性能受表面复合速率变化的影响很小;但复合速率超过1×103cm/s后,电池转换效率快速下降。背表面复合对电池效率影响则更明显,当背表面复合速率超过1×104cm/s后,电池转换效率急剧下降,在背表面复合速率增大到1×106cm/s时,电池效率下降到不足5%,而在电池背表面复合速度较小时(10~103cm/s)则可获得较高的转换效率。     

磷铝吸杂在多晶硅太阳电池中的应用

研究了多晶硅的浓磷扩散吸杂、铝吸杂、磷-铝联合吸杂(双面蒸铝).采用准稳态光电导衰减法测试了吸杂前后多晶硅片的有效少数载流子寿命,发现磷-铝联合吸杂于硅片少子寿命的提高最大达30μs以上,其次是磷吸杂,铝吸杂再次之.采用吸杂后的多晶硅片制备了1cm×1cm的太阳电池,与相同条件下未经吸杂制备的电池相比,发现三种吸杂方式都能提高电池的各项电学特性,其中磷-铝联合吸杂提高电池效率最大,达40%以上,最差为铝吸杂,只有15%左右的提高,这与吸杂后所测得的少子寿命的变化趋势一致.实验说明三种吸杂方式在不同程度上促成了硅片界面晶格应力对重金属杂质的吸附作用,减少了载流子的复合中心,从而提高了有效少数载流子的寿命;而有效少数载流子的寿命直接影响到电池的效率.     

晶体硅/氧化钨背异质结太阳电池的制备及性能研究

采用热蒸发法制备了n型晶体硅/氧化钨(WOx)异质结,并将其应用于背结太阳电池,研究了不同背电极对电池性能的影响及电池的变温性能.结果表明:相对于背铝电极,背银电极能够有效地提升电池的光电转换性能,最高光电转换效率达到了15.1％.结合Sun-Voc测试,证实通过降低电池串联电阻可使其光电转换效率提升至17.2％.电池...     

光致发光技术在Si基太阳电池缺陷检测中的应用

太阳电池的缺陷往往限制了其光电转化效率和使用寿命。利用光致发光原理获取晶体Si太阳电池的荧光照片,用以诊断其缺陷。外界的光能在Si中被吸收,产生非平衡少数载流子,而一部分载流子的复合是以发光形式来完成的。发出的光子可以被灵敏的CCD相机获得,得到太阳电池的辐射复合分布图像。这种光强分布反映出非平衡少数载流子的数目分布,裂痕和缺陷处表现为较低的光致发光强度。这里关注的是单晶Si太阳电池的检验。在室温条件下电池的裂痕和缺陷可以快速予以检测,验证了"光致发光效应"有潜力成为流水线式检测产品的手段。     

晶体硅太阳电池减反射膜的研究

在太阳电池表面形成一层减反射薄膜是提高太阳电池的光电转换效率比较可行且降低成本的方法。应用PECVD（等离子体增强化学气相沉积）系统,采用SiH4和NH3气源以制备氮化硅薄膜。研究探索了PECVD生长氮化硅薄膜的基本物化性质以及在沉积过程中反应压强、反应温度、硅烷氨气流量比和微波功率对薄膜性质的影响。通过大量实验,分析了氮化硅薄膜的相对最佳沉积参数,并得出制作减反射膜的优化工艺。     

晶体硅太阳电池的双层结构钝化膜研究

针对目前基于p型硅片制备的单结太阳电池进一步提高表面钝化膜生产效率,利用氮化硅(SiNx)薄膜良好的钝化效果与价格低廉的二氧化钛(TiO2)膜,降低SiNx镀膜厚度减薄对少子寿命的影响。在单晶硅片表面先用PECVD法沉积SiNx薄膜,然后用热喷涂沉积TiO2薄膜。对比测试了热喷涂沉积TiO2薄膜前后电池的性能,结果表明在SiNx膜上增加TiO2膜层后少子寿命明显提高,这可能是TiO2膜结构内存在固定正电荷所致。这种双层结构封装后的太阳电池显示出了较好的光学与电学性能,对进一步改进太阳电池性能具有重要参考价值。     

铝背场对单晶硅太阳电池输出特性的影响

利用PCID软件模拟了n~+/p-p~+结构的单晶硅太阳电池铝背场与硅片厚度对其输出特性的影响.结果表明,有铝背场时太阳电池获得明显的开路电压、短路电流以及光电转换效率的增益;硅片厚度越小,铝背场对其输出特性的影响越大;在有铝背场情况下,硅片厚度为120μm时,可获得最大的光电转换效率.

Abstract：

The PC1D was usecl to simulate the influence of Al-BSF and wafer thickness on electrical properties of n~+/p-p~+ structural monocrystalline silicon solar cells. It is found that solar cells with the Al-BSF structure can gain obvious open circuit voltage, short-circuit current, as well as photoelectric conversion efficiency; the smaller the wafer thickness is, the bigger of the effect of Al BSF works on the electrical properties; when the wafer thickness is 120 m, the solar cells can get the biggest photoelectric conversion efficiency.     

磷铝吸杂在多晶硅太阳电池中的应用

研究了多晶硅的浓磷扩散吸杂、铝吸杂、磷-铝联合吸杂(双面蒸铝)．采用准稳态光电导衰减法测试了吸杂前后多晶硅片的有效少数载流子寿命，发现磷铝联合吸杂于硅片少子寿命的提高最大达30μs以上，其次是磷吸杂，铝吸杂再次之．采用吸杂后的多晶硅片制备了1cm×1cm的太阳电池，与相同条件下未经吸杂制备的电池相比，发现三种吸杂方式都能提高电池的各项电学特性，其中磷铝联合吸杂提高电池效率最大，达40％以上，最差为铝吸杂，只有15％左右的提高，这与吸杂后所测得的少子寿命的变化趋势一致．实验说明三种吸杂方式在不同程度上促成了硅片界面晶格应力对重金属杂质的吸附作用，减少了载流子的复合中心，从而提高了有效少数载流子的寿命；而有效少数载流子的寿命直接影响到电池的效率．     

太阳能电池的电势诱导衰减及检测

晶体硅组件的电势诱导衰减是现在的晶体硅电池组件在高电压系统下广泛面临的失效模式。常规组件的测试方法需要至少96小时的测试时间。在本文中,我们试图通过实验找到一种快速的太阳能电池的抗电势诱导衰减性能的方法。采用NaCl溶液作为Na+源, PVB 作为封装材料,我们能够在1小时内完成实验。在使用了新的抗电势诱导衰减工艺的太阳能电池上也成功进行了测试。经过试验证明实验前后电池片的反向电流的变化是很重要的判断标准。通常具有抗电势诱导衰退性能的电池反向漏电试验后变化是小于2倍的。电池的结果和相对应的组件的测试结果进行了比较,结果显示两者吻合的很好。     

Thermal oxidation for crystalline silicon solar cells exceeding 19% efficiency applying industrially feasible process technology

Thermal oxides are commonly used for the surface passivation of high‐efficiency silicon solar cells from mono‐ and multicrystalline silicon and have led to the highest conversion efficiencies reported so far. In order to improve the cost‐effectiveness of the oxidation process, a wet oxidation in steam ambience is applied and experimentally compared to a standard dry oxidation. The processes yield identical physical properties of the oxide. The front contact is created using a screen‐printing process of a hotmelt silver paste in combination with light‐induced silver plating. The contact formation on the front requires a short high‐temperature firing process, therefore the thermal stability of the rear surface passivation is very important. The surface recombination velocity of the fired oxide is experimentally determined to be below S ≤ 38 cm/s after annealing with a thin layer of evaporated aluminium on top. Monocrystalline solar cells are produced and 19·3% efficiency is obtained as best value on 4 cm² cell area. Simulations show the potential of the developed process to approach 20% efficiency. Copyright © 2008 John Wiley & Sons, Ltd.     

Gettering by heat thermal processing: application in crystalline silicon solar cells

The aim of this work is to getter unwanted impurities from solar grade crystalline silicon (Si) wafers and then to enhance their electronic properties. This was done by forming a sacrificial porous silicon (PS) layer on both sides of the Si wafers and by performing infrared (IR) thermal annealing treatments (at around 950 °C) in a SiCl₄/N₂ controlled atmosphere. The process allows concentrating unwanted impurities in the PS layer and near the PS/silicon interface. These treatments reduce the resistivity by about two orders of magnitude at a depth of about 40 μm and improve the minority carrier diffusion length from 75 to 210 μm. This gettering method was also tested on silicon wafers where grooved fingers and back contacts were achieved using a chemical vapor etching (CVE) method. Front buried metallic contacts and small holes for local back surface field were then achieved after the gettering stage in order to realize silicon solar cells. It was shown that the photovoltaic parameters of gettered silicon solar cells were improved as regard to ungettered ones.     

Silica nanospheres as back surface reflectors for crystalline silicon thin‐film solar cells

In this paper, fabrication of a non‐continuous silicon dioxide layer from a silica nanosphere solution followed by the deposition of an aluminium film is shown to be a low‐cost, low‐thermal‐budget method of forming a high‐quality back surface reflector (BSR) on crystalline silicon (c‐Si) thin‐film solar cells. The silica nanosphere layer has randomly spaced openings which can be used for metal‐silicon contact areas. Using glass/SiN/p⁺nn⁺ c‐Si thin‐film solar cells on glass as test vehicle, the internal quantum efficiency (IQE) at long wavelengths (>900 nm) is experimentally demonstrated to more than double by the implementation of this BSR, compared to the baseline case of a full‐area Al film as BSR. The improved optical performance of the silica nanosphere/aluminium BSR is due to reduced parasitic absorption in the Al film. Copyright © 2007 John Wiley & Sons, Ltd.     

Ultra‐low concentration Na2CO3/NaHCO3 solution for texturization of crystalline silicon solar cells

In this work, a novel diluted carbonate/bicarbonate solution was applied for texturization of monocrystalline silicon for solar cells. The content of reactants in the solution was decreased 20 times with respect to the previously optimum found by our group and 12 times with respect to the lowest values reported in the literature as optimum. The use of this low‐cost and nonhazardous solution, free of additives as isopropyl alcohol, can reduce costs in solar cell processing. Copyright © 2011 John Wiley & Sons, Ltd.     

Optimization of anti‐reflection moth‐eye structures for use in crystalline silicon solar cells

An anti‐reflection (AR) moth‐eye structure made of acrylic resin and deposited on a polyethylene terephthalate (PET) substrate was optimized in the wavelength range from 400 to 1170 nm; crystalline silicon (c‐Si) solar cells function efficiently in this wavelength range. The rigorous coupled wave analysis (RCWA) method was used for optical simulation, and the Taguchi method was used for efficient optimization. The simulation results showed that the reflectance of the optimized structure over the above‐mentioned wavelength range was less than 0.87% and that a minimal reflectance of 0.1% was observed at 400 nm. Experimental results showed that the reflectance of a fabricated moth‐eye structure was less than 1.0% in the wavelength range and that a minimal reflectance of 0.55% was observed at 700 nm. A c‐Si solar cell, which was enclosed in a polyvinyl butyral (PVB) layer of uniform thickness, was coated with the fabricated moth‐eye film, and it was observed that the moth‐eye film increased electric generation (EG) up to 15%, depending on the incident angle. Further, a daily increase in EG of up to 8.7% was estimated on a clear summer day in Japan when the moth‐eye film was used. Copyright © 2010 John Wiley & Sons, Ltd.     

Diffractive gratings for crystalline silicon solar cells—optimum parameters and loss mechanisms

In this paper, we present guidelines for the design of backside gratings for crystalline silicon solar cells. We use a specially developed method based on a combination of rigorous 3D wave optical simulations and detailed semiconductor device modeling. We also present experimental results of fabricated structures. Simulation‐based optimizations of grating period Λ and depth d of a binary grating and calculations of the optical and electrical characteristics of solar cells with optimized gratings are shown. The investigated solar cell setup features a thickness of d_bulk = 40 µm and a flat front surface. For this setup, we show a maximum increase in short‐circuit current density of Δj_SC = 1.8 mA/cm² corresponding to an efficiency enhancement of 1% absolute. Furthermore, we investigate different loss mechanisms: (i) an increased rear surface recombination velocity S_0,b because of an altered surface caused by the introduction of the grating and (ii) absorption in the aluminum backside reflector. We analyze the trade‐off point between gain due to improved optical properties and loss due to corrupted electrical properties. We find that, increasing the efficiency by 1% absolute due to improved light trapping, the maximum tolerable recombination velocity is S_0,b(max) = 5.2 × 10³ cm/s. From simulations and measurements, we conclude that structuring of the aluminum backside reflector should be avoided because of parasitic absorption. Adding a dielectric buffer layer between silicon and the structured aluminum, absorption losses can be tuned. We find that for a planar reflector, the thickness of a SiO₂ buffer layer should exceed = 120 nm. Copyright © 2011 John Wiley & Sons, Ltd.     

扩散温度和时间对晶体硅太阳电池性能的影响

研究了薄层方块电阻对单晶硅太阳电池的开路电压(Voc)、短路电流(Isc)、填充因子(FF)和转换效率(η)的影响。通过控制扩散温度和时间制备了具有不同薄层方块电阻的单晶硅太阳电池。结果表明:当扩散温度和时间分别为863℃和1 050 s时,电池性能得到了有效的改善,其平均开路电压、短路电流、填充因子和转换效率分别为0.64 V,5.58 A,0.755和17.3%。     

Optimization of Al_2O_3/SiN_x stacked antireflection structures for N-type surface-passivated crystalline silicon solar cells

In the case of N-type solar cells,the anti-reflection property,as one of the important factors to further improve the energy-conversion efficiency,has been optimized using a stacked Al₂O₃/SiN_x layer.The effect of SiN_x layer thickness on the surface reflection property was systematically studied in terms of both experimental and theoretical measurement.In the stacked Al₂O₃/SiN_x layers,results demonstrated that the surface reflection property can be effectively optimized by adding a SiN_x layer,leading to the improvement in the final photovoltaic characteristic of the N-type solar cells.