高效单晶硅太阳电池的研制

简述了高效单晶硅太阳电池的初步研制结果。对电阻率不同的ＣＺ和ＦＺ材料和不同的电池结构进行了实验。为了提高效率，对发射区钝化工艺、分区轻（ｎ＾＋）重（ｎ＾＋＋）扩散、背场、表面织构化技术和氯清洗等工艺进行试验研究。目前制备的最好电池，其效率为１８．６３％。     

单晶硅太阳电池组件的热击穿

论述了单晶硅太阳电池组件中存在的热击穿现象,这是不同于组件热斑效应的另一种物理现象,它对组件的寿命可靠性会构成威胁。对引起太阳电池组件热击穿的原因进行了分析,并提出相关解决方法。     

烧结工艺对薄片单晶硅太阳电池弯曲的影响

通过在快速热处理(Rapid Thermal Processor,RTP)炉中模拟铝背烧结过程,研究了升温速率、烧结温度和降温速率等烧结工艺参数对薄片单晶硅太阳电池弯曲的影响.结果显示,增加铝熔化前和减少铝熔化后的处理时间、加快降温以及降低烧结温度都能减小电池片弯曲.这主要是由于这些烧结工艺参数影响了铝层的致密度和降温过程中AlSi熔体的过冷所致.在此基础上得出了减小电池片弯曲的合理烧结工艺.     

常规单晶硅太阳电池在低倍聚光条件下应用研究

利用常规单晶硅光伏电池，在进行输出特性研究的基础上，设计研制出带有非对称复合抛物面聚光器的光伏发电系统。该系统利用聚光器的有效聚光比随季节的变化，使光电池上接收到的太阳辐射量全年相对均衡，结果不仅降低了发电成本而且可改善系统的可靠性。     

表面损伤对单晶硅太阳电池制绒的影响

研究了不同温度、不同浓度碱溶液去除单晶硅亚表面损伤对单晶硅太阳电池制绒的影响。结果显示,在对亚表面损伤的去除过程中,硅片在不同腐蚀条件下反应的开始阶段和后期表面形貌差异较大。在20%KOH溶液中反应40s后的硅片制绒5min后形成的小凸起远大于在20%KOH溶液中反应100s的硅片制绒5min后形成的小凸起。在20%KOH溶液中反应40s的硅片在制绒过程中金字塔结构的长大不是按照理想的(111)面进行的,而反应100s的硅片制绒过程中金字塔结构的长大则更加规则。     

背电极花样对单晶硅太阳电池机械性能的影响

用三点弯方法研究了3种不同背电极花样的单晶硅太阳电池前后主电极附近以及铝背场和细栅区域的机械性能,初步探讨了背电极花样对断裂强度的影响。研究表明:背电极花样对太阳电池的断裂强度有明显影响,通过改进背电极花样能够有效提高太阳电池的机械性能,降低其破碎率。     

单晶硅片表面金字塔尺寸对太阳电池电性能的影响

针对单晶硅片表面金字塔绒面对太阳电池电性能的影响,对比3款制绒添加剂A、B、C对金字塔绒面尺寸、均匀性、出绒率、比表面积及反射率的差异,分析了不同绒面结构对太阳电池的光电转换效率和漏电流的影响。分析结果表明：金字塔大小均匀、高度高,比表面积大的绒面可有效提升太阳电池的光电转换效率,出绒率及反射率对太阳电池的光电转换效率影响不大,但随着金字塔高度变高,塔尖变尖锐,选择性发射极激光重掺时容易造成塔尖消融,碱抛时对正面的保护作用减弱,易对重掺区的p-n结产生破坏,导致漏电流增大。     

反应离子刻蚀法制绒在单晶硅太阳电池上的应用

研究了在预制绒基片上进行RIE织构化处理,得到的硅片表面具有很好的陷光效果,平均反射率仅为6%左右。通过热氧化法改善表面损伤,发现在温度900℃下,氧化膜厚度为40nm时,可得到较高的有效少子寿命,由此制得电池的内量子效率(IQE)、短路电流密度均有提高。     

Industrial manufacturing of semitransparent crystalline silicon POWER solar cells

This paper gives an extract of the state of the art of the manufacturing of semitransparent crystalline silicon POWER solar cells in an industrial environment. A short introduction of the POWER devices concept (see Fig. 1) will be given followed by an insight in the applied production process. Finally, examples effecting the efficiency distribution in the cell production and their solutions are given. It is believed that the lessons we learned in optimising the manufacturing process and production line of transparent POWER solar cells can be helpful for the increasing activities in the direction of thin wafers as well as novel solar cell devices.     

Pilot production of concentrator silicon solar cells: Approaching industrialization

Using a simple process, high-efficiency silicon concentrator solar cells have proved to achieve up to 21% efficiency at 100×. The purpose of this work is to prove the feasibility of their industrialisation by setting up a pilot line and manufacturing a significant number of cells for a 100× concentrator system. The process has been successfully verified by modifying the antireflection coating, the annealing process and the back contact. This yielded an average efficiency of 18.5% at 100× with 70% of cells having an efficiency >18% and costs ranging from 0.31 to 0.41 €/W. A fast learning curve is shown which suggests optimistic results indeed for further industrialisation.     

Development of low cost production technologies for polycrystalline silicon solar cells

To develop a technology of forming grooves for low cost cell production, a multi-blade wheel grinding method was investigated. The process time of groove formation on the surface of 10 × 10 cm² polycrystalline silicon substrate was reduced to 30 s by a newly developed high-speed groove formation machine. Simultaneous formation of junction and anti-reflection coating by atmospheric pressure chemical vapor deposition (APCVD) technique was also investigated. For electrodes formation process, single firing method for both side electrodes made possible to simplify the firing process and to speed up from a conventional speed of 400 mm/min to 5000 mm/min.     

Flexible silicon solar cells

In order to be useful for certain niche applications, crystalline silicon solar cells must be able to sustain either one-time flexure or multiple non-critical flexures without significant loss of strength or efficiency. This paper describes experimental characterisation of the behaviour of thin crystalline silicon solar cells, under either static or repeated flexure, by flexing samples and recording any resulting changes in performance. Thin SLIVER cells were used for the experiment. Mechanical strength was found to be unaffected after 100,000 flexures. Solar conversion efficiency remained at greater than 95% of the initial value after 100,000 flexures. Prolonged one-time flexure close to, but not below, the fracture radius resulted in no significant change of properties. For every sample, fracture occurred either on the first flexure to a given radius of curvature, or not at all when using that radius. In summary, for a given radius of curvature, either the flexed solar cells broke immediately, or they were essentially unaffected by prolonged or multiple flexing.     

Amorphous silicon solar cells

The perfectioning of the deposition techniques of amorphous silicon over large areas, in particular film homogeneity and the reproducibility of the electro-optical characteristics, has allowed a more accurate study of the most intriguing bane of this material: the degradation under sun-light illumination. Optical band-gap and film thickness engineering have enabled device efficiency to stabilize with only a 10–15% loss in the as-deposited device efficiency. More sophisticated computer simulations of the device have also strongly contributed to achieve the highest stable efficiencies in the case of multijunction devices. Novel use of nanocrystalline thin films offers new possibilities of high efficiency and stability. Short term goals of great economical impact can be achieved by the amorphous silicon/crystalline silicon heterojunction. A review is made of the most innovative achievements in amorphous silicon solar cell design and material engineering.     

Thin crystalline silicon solar cells

A 50 μm thin layer of high quality crystalline silicon together with efficient light trapping and well passivated surfaces is in principle all that is required to achieve stable solar cell efficiencies in the 20% range. In the present work, we propose to obtain these layers by directly cutting 50 μm thin wafers from an ingot with novel cutting techniques. This development is discussed in the frame of a defect tolerant mass production scenario and aims at obtaining twice the amount of wafers as compared to present wire/slurry technology. The ability to process such mechanically flexible wafers into solar cells with standard laboratory equipment is experimentally verified.     

High-efficiency silicon space solar cells

SHARP's activities on Si solar cells developments and features of Si solar cells for space use in comparison with GaAs solar cells are presented. Two types of high-efficiency silicon solar cells and the same kinds of high-efficiency solar cells with integrated bypass function (IBF cells) were developed and qualified for space applications. The NRS/LBSF cells and NRS/BSF cells showed an average of 18% and 17% efficiencies, respectively, at AMO and 28°C conditions. The IBF cells have P⁺N⁺ diodes on the front surface to protect itself from reverse voltage due to shadowing. The designs and features of these solar cells are presented. The radiation tests results of these solar cells are also presented. The NRS/BSF cells showed lower degradation rate compared to conventional BSFR cells with the same thickness (100 μm). But the NRS/LBSF cells showed a higher degradation rate than the BSFR cells. The IBF cells showed almost the same radiation characteristics as the same kinds of cells without IBF. The results of radiation tests on these high-efficiency solar cells and the discussions about the radiation characteristics of them are presented. In the last section, the future silicon solar cell development plan is discussed.     

Multicrystalline silicon solar cells with porous silicon emitter

A review of the application of porous silicon (PS) in multicrystalline silicon solar cell processes is given. The different PS formation processes, structural and optical properties of PS are discussed from the viewpoint of photovoltaics. Special attention is given to the use of PS as an antireflection coating in simplified processing schemes and for simple selective emitter processes as well as to its light trapping and surface passivating capabilities. The optimization of a PS selective emitter formation results in a 14.1% efficiency mc-Si cell processed without texturization, surface passivation or additional ARC deposition. The implementation of a PS selective emitter into an industrially compatible screenprinted solar cell process is made by both the chemical and electrochemical method of PS formation. Different kinds of multicrystalline silicon materials and solar cell processes are used. An efficiency of 13.2% is achieved on a 25 cm² mc-Si solar cell using the electrochemical technique while the efficiencies in between 12% and 13% are reached for very large (100–164 cm²) commercial mc-Si cells with a PS emitter formed by chemical method.     

Concentrator silicon solar cells from silicon industry rejects

Two types of silicon (Si) substrates (40 n-type with uniform base doping and 40 n/n⁺ epitaxial wafers) from the silicon industry rejects were chosen as the starting material for low-cost concentrator solar cells. They were divided into four groups, each consisting of 20 substrates: 10 are n/n⁺ and 10 are n substrates, and the solar cells were prepared for different diffusion times (45, 60, 75 and 90 min). The fabricated solar cells on n/n⁺ substrates (prepared with a diffusion time of 75 min) showed better parameters. In order to improve their performances, particularly the fill factor, 20 new solar cells on n/n⁺ substrates were fabricated using the same procedure (the diffusion time was 75 min)—but with four new front contact patterns. Investigation of current–voltage (I–V) characteristics under AM 1.5 showed that the parameters of these 20 new solar cells have improved in comparison to previous solar cells' parameters, and were as follows: open-circuit voltage (V_OC=0.57 V); short circuit current (I_SC=910 mA), and efficiency (η=9.1%). Their fill factor has increased about 33%. The I–V characteristics of these solar cells were also investigated under different concentration ratios (X), and they exhibited the following parameters (under X=100 suns): V_OC=0.62 V and I_SC=36 A.