玻璃中PbO含量对太阳能电池正面银浆欧姆接触性能的影响

正面银浆是晶体太阳能电池金属化的关键材料,玻璃中铅组分在达到银浆与硅片良好的欧姆接触中起着重要作用。用TGA-DSC和SEM对无铅玻璃及含铅玻璃特性进行了表征。结果表明,含铅玻璃Tg低,放热量高,溶Ag能力强,在降温过程中析出的银颗粒数量占优、粒径细小、排列规则、分布均匀,因此有较好的欧姆接触。研究了不同PbO含量的玻璃对不同方阻硅片电性能的影响,结果显示,随着硅片方阻的提高,增加玻璃中PbO含量有助于改善与Si发射极的欧姆接触,但PbO含量过高,溶Ag量过大,玻璃对Si发射极腐蚀较深,导致P-N结破坏严重,漏电较大,Voc下降明显。PbO含量在15%～25%,欧姆接触较好,Voc影响较小,故有较好的电池转换效率。     

硅异质结太阳能电池用透明导电氧化物薄膜的研究现状及发展趋势

硅异质结(SHJ)太阳能电池是目前光伏产业中的重要组成部分,其由于具有高开路电压(V_oc)等优点而引起了广泛的关注。在硅异质结太阳能电池中,透明导电氧化物(TCO)薄膜层的光学性能和电学性能分别影响着电池的短路电流(J_sc)、填充因子(FF),进而影响电池的转换效率。近年来,SHJ电池中TCO层的研究主要集中于掺杂的In₂O₃和ZnO体系。本文从硅异质结太阳能电池的不同结构出发,概述了TCO薄膜的光电性能(透过率、禁带宽度、方块电阻、载流子浓度、迁移率和功函数)以及与相邻层的接触对电池性能的影响,介绍了不同体系的透明导电氧化物薄膜在硅异质结太阳能电池中的应用及研究现状,并展望其未来的发展趋势。     

Te-Bi玻璃对晶体硅太阳能电池正银电极性能的影响

正银浆料是晶体硅太阳能电池金属化的关键材料, 环保型浆料是正银电极的主要发展方向之一。通过正交实验方法, 研究了不同配方和组分的Te-Bi玻璃对正银电极性能的影响。用TGA-DSC分析了Te-Bi玻璃和正银浆料的热处理特性, 用SEM分析了Ag-Si界面处银微晶的分布和大小, 利用隧道电流模型分析了玻璃对正银电极性能的影响规律。结果表明: TeO₂含量45wt%, Bi₂O₃含量36wt%的Z7玻璃, 其T_g为379.07℃, 对应的正银浆料在612.8℃出现吸热反应, 同时发生失重(-0.16%), 制作的多晶硅电池效率达到16.87%, 电极的附着力达到4.35 N。     

高效单晶硅太阳电池的最新进展及发展趋势

晶体硅太阳电池是目前光伏市场的主流产品,其又可分为多晶硅电池和单晶硅(c-Si)电池。目前,多晶硅电池成本较低,市场份额较大,但其效率较低;单晶硅电池成本相对偏高,但其效率更高,市场份额小于多晶硅电池。随着硅材料和硅片切割技术的进步,单晶硅片的成本持续下降,且未来市场对高效率的高端光伏产品需求日益增长。因此,高效率的单晶硅电池将受到更多的关注。为进一步提高单晶硅太阳电池的效率,近几年的研究工作主要集中于提高硅片质量来降低体缺陷,寻找新型钝化材料来降低表面和界面缺陷,开发先进的减反技术(新型的绒面陷光结构和材料)以提高光的利用率,引入低电阻金属化技术降低串联电阻,优化PN结制备技术以及器件结构等。2014年至今,单晶硅太阳电池的转换效率得到连续突破。目前,最高效率是日本Kaneka公司创造的26.6%,其他效率达到或者超过25%的晶硅电池包括钝化发射极背面局部场接触(PERL)电池、交叉指式背接触(IBC)电池、硅异质结(SHJ)电池、交叉指式背接触异质结(HBC)电池、隧穿氧化层钝化接触(TOPCon)电池、多晶硅氧化物选择钝化接触(POLO)电池等。分析这些典型电池的关键技术可以发现,栅线电极与c-Si的金属-半导体接触复合成为影响电池效率的关键因素。为减小这些复合,一方面通过电池背面局部开孔来减小金属与c-Si直接接触的面积,包括钝化发射极背场点接触(PERC)、PERL、钝化发射极和背面全扩散(PERT)等电池。另一方面则是开发既能够实现优异的表面钝化,同时又无需开孔便可分离与输运载流子的新型载流子选择性钝化接触技术,如SHJ电池、TOPCon电池等。此外,采用交叉指式背接触技术与其他电池结构结合则是最大限度提高光利用率的必然选择,包括IBC电池和HBC电池。本文介绍了当前国际上转化效率达到或超过25%的典型高效单晶硅太阳电池,分别对其器件结构、核心工艺、关键材料等进行了分析,在总结这些高效单晶硅太阳电池各自特点的基础上对该领域的发展前景进行了展望。     

a-Si/CIS叠层太阳能电池的光诱导性能衰退和稳定性分析

基于pin结构a Si∶H太阳能电池中的空间电荷效应 ,讨论a Si/CIS叠层太阳能电池的稳定性。结果表明 ,光生空穴俘获造成的a Si∶H中正空间电荷密度增加改变了电池内部的电场分布 ,普遍抬高a Si∶H薄膜中电场强度。在光照射下 ,空间电荷效应不会给a Si/CIS叠层结构中的a Si∶H薄膜带来准中性区 (低场“死层”) ,因而没有发生a Si/CIS叠层太阳能电池顶电池 (p i na Si∶H)的光诱导性能衰退 ,a Si/CIS叠层结构太阳能电池具有较高的光稳定性。     

Si/PEDOT:PSS异质结太阳能电池研究进展

以有机材料作为空穴传输层的Si/有机杂化太阳能电池由于其器件结构与制备工艺的不断优化,在短期内实现了理论探究与合成应用的快速增长。但有机材料具有的导电性低和复合界面间稳定性差等缺点,严重影响了复合器件的光电转化效率和使用寿命,阻碍了异质结太阳能电池的技术发展与市场应用。在Si/有机杂化太阳能电池领域,聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸盐(PEDOT∶PSS)是目前为止效果最佳的有机半导体。PEDOT∶PSS具有高导电性和高透过率等特点,使其成为一种理想的有机空穴传输层材料,并在异质结太阳能电池技术发展和工业应用中脱颖而出。利用PEDOT∶PSS的高导电性能可实现空穴的有效传输,其较高的透过性降低了P-N结生成过程中的寄生吸收,并且在制备中免去了传统硅基太阳能电池所需的高温环节,有效地降低了实际生产成本。近五年来,为降低PEDOT∶PSS中绝缘的PSS对电子传输和表面复合性的影响,大量学者进行了掺杂改性和界面设计的研究工作,有效降低了绝缘性PSS带来的影响,充分发挥了PEDOT高透性和高导电率的优势,优化表面陷光性和器件稳定性,实现了光电转化效率从5.09%至17.4%的大幅度跳跃。本文从Si/PEDOT∶PSS异质结太阳能电池的结构与工作原理出发,重点介绍了Si材料和PEDOT∶PSS有机物的表面修饰、PEDOT∶PSS的掺杂改性、界面氧化层改性和对嵌入式微电网电极改造手段及它们对整体器件性能提升的影响等工作,归纳并分析了Si/PEDOT∶PSS杂化太阳能电池的最新研究进展,展望了太阳能电池的技术研发和理论研究,对未来Si/PEDOT∶PSS异质结太阳能电池的实验室技术研发与工业化生产应用具有一定参考意义。     

有机薄膜太阳能电池

有机太阳能电池作为一种新兴的有着巨大潜力的光电转换器件,吸引了越来越多的关注。综述了有机薄膜太阳能电池主要的两种器件结构的研究进展,即基于无机异质结发展出来的双异质结型有机太阳能电池和基于扩展双层异质结活性层受限的接触面积而提出的体异质结型太阳能电池;阐述了这两种器件结构的工作原理、影响有机太阳能电池光电转换效率的因素以及两种结构的不足之处,并展望了有机太阳能电池发展的广阔前景。     

四结太阳能电池InGaP/GaAs/GaInAsN/Ge的设计与模拟

随着多结太阳能电池技术的发展,追求更高效率的四结太阳能电池结构InGaP/GaAs( In-GaAs)/(新材料)/Ge受到广泛的研究.四元化合物材料Ga1-xInxAs1-yNy通过控制其组分比例,其禁带宽度可以调整为0.95ev - 1.05ev,并且可以与GaAs,Ge实现晶格匹配,是应用于新一代太阳能电池最有潜...     

基于全无机CsPbBr3钙钛矿太阳能电池的光电性能研究

钙钛矿太阳能电池具有制作工艺简单和光电转换效率高等优点,成为光伏领域研究的热点。而全无机钙钛矿太阳能材料CsPbBr₃具有较强的稳定性,是具有竞争力的钙钛矿光吸收材料。主要利用SCAPS-1D软件构建了FTO/TiO₂/CsPbBr₃/Cu₂ZnSnS₄(CZTS)/Ag平面异质结结构。研究了全无机钙钛矿材料CsPbBr₃厚度和带隙对钙钛矿太阳能电池的影响。     

银纳米相吸收增强型钙钛矿太阳电池薄膜的制备及性能研究

分别将银纳米相溶胶(银纳米颗粒、Ag@SiO₂核壳结构、银纳米线)掺入氧化铝异丙醇溶液中制成具有蜂窝结构的介孔层材料, 然后在介孔层表面制备CH₃NH₃PbI₃钙钛矿吸收层得到Al₂O₃/CH₃NH₃PbI₃复合薄膜, 并对复合膜的微观结构、光吸收特性及太阳电池器件性能进行了测试和分析。研究表明, Al₂O₃/CH₃NH₃PbI₃复合膜与CH₃NH₃PbI₃在可见光区域吸收光谱基本相同, 含量极少的Al₂O₃对CH₃NH₃PbI₃吸光性能影响较小。而掺入银纳米相可明显改善CH₃NH₃PbI₃钙钛矿薄膜的吸收性能。当银纳米颗粒、Ag@SiO₂核壳结构和银纳米线相对浓度比分别为0.15、0.3及0.15时, CH₃NH₃PbI₃吸光性能分别达到最佳; 银纳米相浓度继续增大时, 薄膜的光吸收性能逐渐减弱。此外, 掺入Ag@SiO₂核壳结构可使钙钛矿薄膜太阳电池光电转换效率由6.28%增大到7.09%, 而银纳米颗粒和银纳米线由于会增大太阳电池内部载流子传输路径, 提高电子空穴对复合效率, 最终反而降低了太阳电池短路电流密度和光电转换效率。     

Impact of interface microstructure on adhesion force between silver paste and silicon solar cells’ emitter

The adhesion strength between silver paste and silicon solar cell’s emitter is a primary source of long-term degradation in solar modules. In this study, the interface microstructure between screen-printed silver thick-film and silicon solar cells’ emitter was studied. Three kinds of commercial silver pastes were printed on silicon solar cells’ emitter to form different Ag–Si contact structures. The interface microstructure between silver paste and emitter was observed by SEM, while the compositions of Ag thick-film were analyzed by EDX. The deductions we got from SEM and EDX were verified by the pull test for the first time. The results presented in this study give some suggestions to the development of silver paste and crystalline silicon solar cells’ fire-through.     

Inclusion of CdSe quantum dots on the P-doped emitter of Si solar cells

We investigated Cadium Selenide quantum dots embedded in the Si solar cell in order to improve the efficiency of conventional Si solar cell. CdSe quantum dots with 3 to approximately 4 nm size were printed on the phospho-silicate glass layer grown over the emitter surface of p-n junction Si solar cells during the phosphorous diffusion process. Ohmic contact was formed by the contribution of nanoparticles at the Si emitter in spite of the existance of phospho-silicate glass layer. The enhanced light absorption due to the quantum dots was ranged from 500 to 600 nm where the CdSe nanodots have the corresponding emission wavelength of 560 nm. The efficiency of reference solar cell with the glass layer was measured to be 1.0% and it was increased to 12.72% for the reference sample without the glass layer. Furthermore, the efficiency of CdSe quantum dot sample was measured to be 13.6%. This indicates that the quantum dots play the roles of both the formation of tunneling channel and the enhancement of the light conversion efficiency in the visible spectral range.     

Investigation of contact resistance between silicon and silver paste made by screen-printing

In this paper, the front contact resistance of screen-printing crystalline silicon solar cells was investigated. By establishing a fine model for silicon and silver paste contact made by screen-printing and fire-through, the three kinds of conduction mechanism were analyzed quantitatively. According to the model, the comprehensive calculation of the contact resistance between silicon and silver paste sintering was made for the first time. The results calculated in this study suggest that the contact resistance of silicon and silver paste is about 1.20 mΩ for 125 mm × 125 mm single crystalline silicon solar cells, this approximately agrees with the measured values. By optimizing composition of silver paste according to our results, the silver consumption per watt can be reduced, and the efficiency of crystalline silicon solar cells can be further improved. The results laid the foundation for studying the screen-printed crystalline silicon solar cell front contact metallization system.     

Fabrication of polycrystalline silicon solar cells showing high efficiency

The paper presents a methodology for fabrication of low-costing silicon solar cells with an efficiency of 10%. A polycrystalline silicon wafer, size 100×100 mm and thickness 450 μm, was doped with phosphorus using POCl₃ as the dopant. While, the backside (p-side) of the wafer was printed with a paste of Ag+Al in the ratio of 25 : 1, the front side (n-side) was printed with a paste of silver. It was fired at 720°C for better ohmic contact. Chemical vapour deposition (CVD) method was adopted for antireflection coating. Pure oxygen gas was bubbled through a solution of TiCl₄ at 200°C. The fabricated cells gave a significant increase in efficiency in terms of open circuit voltage (V) 560 mV, short circuit current (I) of 2·7 amp, and fill factor of 0·73. The methods used are inexpensive, and suitable for production of efficient silicon solar on a commercial basis.     

Fabrication of selective-emitter silicon heterojunction solar cells using hot-wire chemical vapor deposition and laser doping

The Si heterojunction (HJ) solar cells were fabricated on the textured p-type mono-crystalline Si (c-Si) substrates using hot-wire chemical vapor deposition (HWCVD). In view of the potential for the bottom cell in a hybrid junction structure, the microcrystalline Si (μc-Si) film was used as the emitter with various PH₃ dilution ratios. Prior to the n-μc-Si emitter deposition, a 5 nm-thick intrinsic amorphous Si layer (i-a-Si) was grown to passivate the c-Si surface. In order to improve the indium-tin oxide (ITO)/emitter front contact without using the higher PH₃ doping concentration, a laser doping technique was employed to improve the ITO/n-μc-Si contact via the formation of the selective emitter structure. For a cell structure of Ag grid/ITO/n-μc-Si emitter/i-a-Si/textured p-c-Si/Al-electrode, the conversion efficiency (AM1.5) can be improved from 13.25% to 14.31% (cell area: 2 cm × 2 cm) via a suitable selective laser doping process.     

Microgrid Electrode for Si Microwire Solar Cells with a Fill Factor of Over 80%

Here, a novel microgrid top electrode for highly efficient radial‐junction Si microwire solar cells is demonstrated. The microgrid electrode minimizes optical and electrical losses, thus ensuring proper function of the shallow (sheet resistance of ≈100 Ω sq⁻¹) junction emitter. This leads to effective collection of the photocarriers from the shallow junction emitter through the top electrode without severe Auger/surface recombination, improving the overall power conversion efficiency of the Si microwire solar cell. With an optimized microgrid structure, 1 cm² microwire solar cells show a conversion efficiency of up to 16.5%, with an open‐circuit voltage of 565.2 mV and a short‐circuit current density of 35.9 mA·cm⁻²; this conversion efficiency is 72% higher than that of solar cells with an edge electrode (9.6%). Further, an ≈1 μm thick Ni electrode that is formed by electroplating considerably reduces the metal and contact resistances, which reproducibly yields a fill factor of over 80% (max 81.2%). Thus, the use of a novel microgrid to construct an ideal metal/emitter interface presents a unique opportunity to develop highly efficient microwire solar cells.     

SEM and specific contact resistance analysis of screen-printed Ag contacts formed by fire-through process on the shallow emitters of silicon solar cell

The SEM and specific contact resistance measurements of the Ag metal contact formed by applying a fire-through process on the shallow emitter region of the silicon solar cell have been investigated. The metal contact consists of screen-printed Ag paste patterned on the silicon nitride (Si₃N₄) deposited over the n⁺-Si emitter region of the solar cell. The sintering step consists of a rapid firing step at 800 °C or above in air ambient. This is followed by an annealing step at 450 °C in nitrogen ambient. It enables to drive the Ag metal paste onto the Si₃N₄ layer and facilitates the formation of an Ag metal/p-Si contact structure. It serves as the top metallization for the screen-printed silicon solar cell. The SEM measurement shows that sintering of the Ag metal paste at 800 °C or above causes the Ag metal to firmly coalesce with the underlying n⁺-Si surface. A thin layer of conductive glassy layer is also presents at the interface of the Ag metal and n⁺-Si surface. The electrical quality of the contact structure was characterized by measuring the specific contact resistance, ρ _c (in Ω-cm²) using the iteration technique based on the power loss calculation for the solar cell. It shows that best value of ρ _c  = 2.53 × 10⁻⁵ Ω-cm² is estimated for the Ag metal contact sintered at temperature above 800 °C. This value of ρ _c is two orders of magnitude lower than the typical value of ρ _c  = 3 × 10⁻³ Ω-cm² reported previously for the Ag contacts of the solar cell. Such low value of ρ _c for the Ag metal contacts indicates that fire-through process results in excellent ohmic properties. The plot of the ρ _c versus impurity doping level (N _s ) shows that measured value of the ρ _c follows a linear relationship with the N _s as predicted by the theory for the heavily doped semiconductor surface. Hence, carrier injection across the Schottky barrier height is quite appropriate to explain the observed ohmic properties of the Ag metal contacts on the n⁺-Si surface of the silicon solar cell.

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Fabrication and characteristics of n-Si/c-Si/p-Si heterojunction solar cells using hot-wire CVD

A double-side (bifacial) heterojunction (HJ) Si solar cell was fabricated using hot-wire chemical vapor deposition. The properties of n-type, intrinsic and p-type Si films were investigated. In these devices, the doped microcrystalline Si layers (n-type Si for emitter and p-type Si for back contact) are combined with and without a thin intrinsic amorphous Si buffer layer. The maximum temperature during the whole fabrication process was kept below 150 °C. The influence of hydrogen pre-treatment and n-Si emitter thickness on performance of solar cells have been studied. The best bifacial Si HJ solar cell (1 cm² sample) with an intrinsic layer yielded an active area conversion efficiency of 16.4% with an open circuit voltage of 0.645 V, short circuit current of 34.8 mA/cm² and fill factor of 0.73.     

Paste Development for an Optimized Filament Stretching Effect during Parallel Dispensing on Transparent Conductive Oxide Layers for Solar Cell Metallization

The availability of silver as an electrically conductive filler material in printing pastes for solar cell metallization is becoming a more crucial issue for multiterawatt-scale production due to its global constraints. Therefore, the silver consumption for solar cell production needs to be reduced drastically by substituting silver with alternative conductive filler materials or utilizing process-specific phenomena. The phenomenon of filament stretching during microextrusion allows significantly lower paste laydowns. The magnitude of filament stretching is paste-dependent and therefore further knowledge of the pastes’ impact to the filament stretching is required. This study presents nine low-temperature curing pastes differing in the particle system and binder resin. The rheological and thermal behavior of these suspensions are investigated and printing tests onto silicon heterojunction (SHJ) precursors are carried out. Additionally, scanning electron microscopy (SEM)-based microstructure analyses of printed electrodes are performed. Based on these experimental results, the impact of paste compositions regarding the paste behavior during microextrusion and the SHJ solar cell performances are analyzed. The developed paste formulations exhibit a strong filament stretching, leading to a reduced silver laydown of down to Δm_Ag = −60%_rel. and an absolute efficiency gain of up to Δη = +0.75%_abs. due to less shading losses.     

Application of power loss calculation to estimate the specific contact resistance of the screen-printed silver ohmic contacts of the large area silicon solar cells

The establishment of a suitable contact formation methodology is a critical part of the technological development of any metal-to-semiconductor contact structure. Many test structures and methodologies have been proposed to estimate the specific contact resistance (ρ_c) of the planar ohmic contacts formed on the heavily doped semiconductor surface. These test structures are usually processed on the same wafer to monitor a particular process. In this study, new experimental procedure has been evolved to assess the value of ρ_c of the screen-printed front silver (Ag) thick-film metal contact to the silicon surface. The essential feature of this methodology is that it is an iteration technique based on the calculation of power loss associated with various resistive components of the solar cell normalized to the unit cell area. Therefore, this method avoids the complexity of making the design of any lay out of a standard contact resistance test structure like transmission line model (TLM) or Kelvin resistor, etc. It was shown that value of specific contact resistance of the order of 1.0 × 10⁻⁵ Ω−cm ² is measured for the Ag metal contacts formed on the n⁺ silicon surface. This value is much lower than the ρ_c data previously reported for the screen-printed Ag contacts. The sintering process of the front metal contact structure at different furnace setting is carried out to understand the possible wet interaction and metal contact formation as a function of the firing. Therefore, the study is further extended to study the peak firing temperature dependence of the ρ_c of screen-printed Ag metal contacts. It will help to assess the specific contact resistance of the ohmic contacts as a function of firing temperature of sintering process.

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