氢退火的BZO前电极对非晶硅薄膜太阳能电池性能的影响

采用低压化学气相沉积方法在玻璃衬底上制备了B掺杂的ZnO（BZO）薄膜,通过氢退火对BZO进行处理,然后作为前电极进行了非晶硅薄膜太阳能电池的制备及性能研究。结果表明：在氢气气氛下退火后,BZO薄膜的载流子浓度基本无变化,但Hall迁移率显著提高,这使得BZO薄膜的导电能力提高;当采用厚度较小、透光率较高的BZO薄膜进行氢退火后作为前电极结构时,非晶硅薄膜太阳能电池的短路电流密度提高0.3~0.4 mA/cm²,电池的转化效率提高0.2%。实验结果可为通过优化前电极结构来提高非晶硅薄膜太阳能电池转化效率提供一种简易的方法。     

前端接触势垒高度对非晶硅和微晶硅异质结太阳电池的影响

运用AMPS-1D（Analysis of Microelectronic and Photonic Structures） 程序系统分析了前端接触（铟锡氧化物）的势垒分别对非晶硅和微晶硅太阳电池性能的影响,比较了两种影响的差异并分析了具体原因. 研究表明：与微晶硅相比,非晶硅受铟锡氧化物功函数Φ_ITO的影响更加显著. 随着Φ_ITO的增加非晶硅的各项物理性能（如太阳电池效率、填充因子等）得到明显改善,而微晶硅的各项参数虽然也随Φ_ITO增加而改变,但更容易趋于饱和. 模拟结果显示,在实际的太阳电池装备过程中可根据前端电极的性能来选择合适的p型硅材料. 关键词： 铟锡氧化物 非晶硅 微晶硅 计算机模拟     

Studies on the polycrystalline silicon/SiO_2 stack as front surface field for IBC solar cells by two-dimensional simulations

Interdigitated back contact(IBC) solar cells can achieve a very high efficiency due to its less optical losses. But IBC solar cells demand for high quality passivation of the front surface. In this paper, a polycrystalline silicon/SiO_2 stack structure as front surface field to passivate the front surface of IBC solar cells is proposed. The passivation quality of this structure is investigated by two dimensional simulations. Polycrystalline silicon layer and SiO_2 layer are optimized to get the best passivation quality of the IBC solar cell. Simulation results indicate that the doping level of polycrystalline silicon should be high enough to allow a very thin polycrystalline silicon layer to ensure an effective passivation and small optical losses at the same time. The thickness of SiO_2 should be neither too thin nor too thick, and the optimal thickness is 1.2 nm.Furthermore, the lateral transport properties of electrons are investigated, and the simulation results indicate that a high doping level and conductivity of polycrystalline silicon can improve the lateral transportation of electrons and then the cell performance.     

Influence of interface states,conduction band offset,and front contact on the performance of a-SiC:H(n)/c-Si(p)heterojunction solar cells

P-type silicon heterojunction(SHJ) solar cells with a-SiC:H(n) emitters were studied by numerical computer simulation in this paper. The influence of interface states, conduction band offset, and front contact on the performance of a-SiC:H(n)/c-Si(p) SHJ solar cells was investigated systematically. It is shown that the open circuit voltage(V_(oc)) and fill factor(F F) are very sensitive to these parameters. In addition, by analyzing equilibrium energy band diagram and electric field distribution, the influence mechanisms that interface states, conduction band offset, and front contact impact on the carrier transport, interface recombination and cell performance were studied in detail. Finally, the optimum parameters for the a-SiC:H(n)/c-Si(p) SHJ solar cells were provided. By employing these optimum parameters, the efficiency of SHJ solar cell based on p-type c-Si was significantly improved.     

Modelling of contact effects in microcrystalline silicon thin-film transistors

Hydrogenated microcrystalline silicon has recently emerged as a promising material system for large-area electronic applications such as thin-film transistors and solar cells. In this paper, thin-film transistors based on microcrystalline silicon were realized with charge carrier mobilities exceeding 40 cm²/Vs. The electrical characteristics of the microcrystalline silicon thin-film transistors are limited by the influence of contact effects. The influence of the contact effects on the charge carrier mobility was investigated for transistors with different dimensions of the drain and source contacts. The experimental results were compared to an electrical model which describes the influence of the drain and source contact dimension on the transistor parameters. Furthermore, the Transmission Line Method was applied to investigate the contact effects of the thin-film transistors with different drain and source contact dimensions. Finally, optimized device geometries like the channel length of the transistor and dimension of the drain and source contacts were derived for the microcrystalline transistors based on the electrical model.     

晶体硅太阳电池金属电极光学损失的理论分析与实验研究

本文基于丝网印刷和丝网印刷后光诱导电镀太阳电池,分析了太阳电池前表面金属电极引起的光学损失的各种情况.考虑到空气-玻璃界面和金属电极两侧边缘区域的反射,通过将金属电极截面近似为半椭圆形模拟了电极的光学损失,计算得到的有效宽度比约为金属电极几何宽度的40%.通过对不同类型样品反射谱的测量计算,同时在理论模拟和实验测量上得到了太阳电池前表面金属电极的光学损失,相应的理论与实验结果相符合. 关键词： 光学损失 有效宽度比 光诱导电镀 反射谱     

Influence of the semiconductor/metal rear contact on the performance of n(a-Si:H)/i(a-Si:H)/p(c-Si) heterojunction solar cells

The aim of this work is to analyze on the results of using of Al/Ag layer as a rear contact to improve the performance of heterojunction silicon solar cells. An analytical method is presented to extract the physical parameters of the equivalent circuit. These parameters are extracted to simulate the I(V) characteristic of heterojunction silicon solar cells, with Al and Al/Ag rear-metal contact. A good agreement between our analytical method and experimental measurement of electrical characteristics is obtained which show clearly how the Al/Ag rear contact can improve the characteristics of silicon solar cells. The influence of the rear-metal contact on the performance of the c-Si(p)-based bifacial HIT solar cell, i.e., the ZnO/Al/a-Si:H(n)/a-Si:H(i)/c-Si(p)/metal solar cell, is investigated in detail by computer simulation using the AFORS-HET software. Accordingly, the design optimization of the bifacial HIT solar cells on c-Si(p) substrates is provided. These simulation show an optimal conversion efficiency of 23% when the rear-metal contact is perfectly ohmic.     

高绒度掺硼氧化锌透明导电薄膜用作非晶硅太阳电池前电极的研究

将自行研制的具有优异陷光能力的掺硼氧化锌用作p-i-n型非晶硅太阳电池的前电极,并且将传统商业用U型掺氟二氧化锡作为对比电极.相比表面较为平滑的掺氟二氧化锡,掺硼氧化锌表面大类金字塔的绒面结构会在本征层生长过程中触发阴影效应,形成大量的高缺陷材料区和漏电沟道,进而恶化电池的开路电压和填充因子.在不修饰掺硼氧化锌表面形貌的情况下,通过调节非晶硅本征层的沉积温度来消弱高绒度表面形貌引起的这种不利影响,对应的电池开路电压和填充因子均出现提升.在仅有铝背电极的情况下,在本征层厚度为200 nm的情况下,以掺硼氧化锌为前电极的非晶硅太阳电池转换效率达7.34%(开路电压为0.9 V,填充因子为70.1%,短路电流密度11.7 mA/cm2).     

免掺杂、非对称异质接触晶体硅太阳电池的研究进展

免掺杂、非对称异质接触的新型太阳电池由于近几年的飞速发展,理论转化效率已达到28%,具有较大的发展空间,引起了人们的重视.由于传统晶硅太阳电池产业存在生产设备成本高、原材料易燃易爆等诸多限制,市场对太阳电池产业低成本、绿色无污染的期待越来越高,极大地增加了免掺杂、非对称异质接触的新型太阳电池研究和开发的必要性.为了进一步加快免掺杂、非对称异质接触晶体硅太阳电池的研究进度,本文对其发展现状进行了综述,着重讨论了过渡金属氧化物(TMO)载流子选择性运输的基本原理、制备技术以及空穴传输层、电子传输层和钝化层对基于TMO构建的免掺杂、非对称异质接触(DASH)太阳电池性能的影响,以期对电池的工作机理、材料选择有更深刻的认识,为新型高效的DASH太阳电池制备提供指导.     

载流子选择性接触:高效硅太阳电池的选择

太阳电池可看成由光子吸收层和接触层两个基本单元组成,接触层是高复合活性金属界面和光子吸收层之间的区域.为了进一步提高硅太阳电池的转换效率,关键是降低光子吸收层和接触之间的复合损失.近年来,载流子选择性接触引起了光伏界的研究兴趣,其被认为是接近硅太阳电池效率理论极限的最后的障碍之一.本文分析了三种类型的载流子选择性接触:在光子吸收层与金属界面之间引入薄的重掺杂层,即所谓的发射极或背面场;利用两种材料之间的导带或价带对齐;利用高功函数的金属氧化物与晶硅接触从而在晶硅中感应能带弯曲.基于一维太阳电池模拟软件wx AMPS,模拟了扩散同质结硅太阳电池[结构为(p~+)c-Si/(n)c-Si/(n~+)c-Si]、非晶硅薄膜硅异质结太阳电池[结构为(p~+)a-Si/(i)a-Si/(n)c-Si/(i)a-Si/(n~+)a-Si]和氧化物薄膜硅异质结太阳电池[结构为(n)MoO_x/(n)c-Si/(n)TiO_x]暗态下的能带结构和载流子浓度的空间分布,其中c-Si为晶硅;a-Si为非晶硅;(i),(n)和(p)分别表示本征、n型掺杂和p型掺杂.模拟结果表明:载流子选择性接触的核心是在接触处晶硅表面附近形成载流子浓度空间分布的不对称进而使得电导率的不对称,形成了对电子的高阻和空穴的低阻或者对空穴的高阻和电子的低阻,从而让空穴轻松通过同时阻挡电子,或者让电子轻松通过同时阻挡空穴,形成空穴选择性接触或者电子选择性接触.     

Ion implantation into amorphous Si layers to form carrier‐selective contacts for Si solar cells

This paper reports our findings on the boron and phosphorus doping of very thin amorphous silicon layers by low energy ion implantation. These doped layers are implemented into a so‐called tunnel oxide passivated contact structure for Si solar cells. They act as carrier‐selective contacts and, thereby, lead to a significant reduction of the cell's recombination current. In this paper we address the influence of ion energy and ion dose in conjunction with the obligatory high‐temperature anneal needed for the realization of the passivation quality of the carrier‐selective contacts. The good results on the phosphorus‐doped (implied V_oc = 725 mV) and boron‐doped passivated contacts (iV_oc = 694 mV) open a promising route to a simplified interdigitated back contact (IBC) solar cell featuring passivated contacts. (© 2014 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

晶体硅太阳电池双层电极优化分析与实验研究

相对于单层电极结构,优化的前表面双层电极能够明显减小功率损失,改善晶体硅太阳电池的电学特性．本文对晶体硅太阳电池的双层电极进行了优化分析和实验研究.通过扫描电子显微镜观测将双层电极的截面抽象为更接近于实际的半椭圆型,建立了太阳电池前表面的双层电极模型,理论分析了双层电极的电学损失和光学损失.结合丝网印刷后光诱导电镀太阳电池的实验,得到了理论和实验上的最优化光诱导电镀增厚电极厚度与丝网印刷电极宽度的关系.所得到的理论和实验结果符合良好.由于并不涉及电极制备的具体技术,双层电极理论模型普遍适用于多种类型的双层电极结构.     

Silicon nitride/silicon oxide interlayers for solar cell passivating contacts based on PECVD amorphous silicon

This Letter demonstrates improved passivating contacts for silicon solar cells consisting of doped silicon films together with tunnelling dielectric layers. An improvement is demonstrated by replacing the commonly used silicon oxide interfacial layer with a silicon nitride/silicon oxide double interfacial layer. The paper describes the optimization of such contacts, including doping of a PECVD intrinsic a‐Si:H film by means of a thermal POCl₃ diffusion process and an exploration of the effect of the refractive index of the SiN_x. The n⁺ silicon passivating contact with SiN_x /SiO_x double layer achieves a better result than a single SiN_x or SiO_x layer, giving a recombination current parameter of ～7 fA/cm² and a contact resistivity of ～0.005 Ω cm², respectively. These self‐passivating electron‐selective contacts open the way to high efficiency silicon solar cells. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Application of stain-etched porous silicon in light emitting diodes and solar cells

Porous silicon/c-Si heterostructures have been formed by the method of stain etching.The properties of light emitting diodes (LED) and solar cells have been studied. The transport mechanism of the diode has been investigated from the current–voltage characteristics measured at different temperatures (296–380 K). A model based on multi-step tunneling of carriers at reverse and low forward bias (<1 V) and on field tunneling across a narrow barrier at higher forward bias (>1.5 V) is proposed for the LED. In the case of the solar cells the porous silicon is formed in between the fingers of the front grid contact. Application of porous silicon in solar cells results in an increase of the short-circuit current and efficiency of the cells by about 30%.     

Enhancement of silicon solar cell performances due to light trapping by colloidal metal nanoparticles

Photovoltaics is the most promising technology for the future of green energy production. To fully realize the potential use of photovoltaic technology, low manufacturing cost and high working photoconversion efficiency must be obtained. Light trapping by metal nanoparticles is an attractive strategy in thin film as well as in bulk silicon solar cells aimed to confine light within the active layer to promote the photon absorption and therefore achieving higher efficiency. In this paper, we tested the deposition of silver and gold nanoparticles on bulk silicon solar cells by colloidal technique in order to enhance their photovoltaic conversion efficiency by means of Plasmonic Light Scattering by metal nanoparticles. The feasible Plasmonic Light Scattering related enhancement was examined using spectral response and I–V measurements. Relative increases of the total delivered power under simulated solar irradiation were observed for cells both with and without antireflection coating using silver and gold nanoparticles.     

In_2O_3:Sn中间层改善B掺杂ZnO薄膜的性能及其应用研究

金属有机化学气相沉积(MOCVD)法生长的掺硼氧化锌(BZO)薄膜,具有天然的"类金字塔"绒面结构,作为硅基薄膜太阳电池的前电极具有良好的陷光效果.但直接获得的BZO薄膜表面形貌过于尖锐,影响后续硅基薄膜材料生长质量及太阳电池的光电转换效率.本文设计了以一层超薄In2O3:Sn(ITO)薄膜(～4 nm厚度)作为中间层的多层膜,并通过对顶层BZO薄膜的厚度调制,改善BZO薄膜的表面特性,薄膜结构为:glass/底层BZO/ITO/顶层BZO.合适厚度的顶层BZO薄膜有助于获得类似"菜花状"形貌特征,尖锐的表面趋于"柔和",而较厚的顶层BZO薄膜仍然保持"类金字塔状"结构."柔和"的BZO薄膜表面结构有助于提高后续生长薄膜电池的结晶质量.将获得的新型"三明治"结构多层膜应用于p-i-n型氢化微晶硅(μc-Si:H)薄膜太阳电池,相比传统的BZO薄膜,电池的量子效率QE在500—800 nm波长范围提高了～10%,并且电池的Jsc和Voc均有所提高.     

Nano‐glass frit for inkjet printed front side metallization of silicon solar cells prepared by sol–gel process

Sol–gel derived nano‐sized glass frits were incorporated into the Ag conductive ink for silicon solar cell metallization. This mixture was specifically formulated for inkjet printing on textured Si wafers with 80 nm thick SiN_x anti reflection coating layers. The correlation between the contact resistance and interface microstructures were studied using scanning electron microscopy and transmission electron microscopy. In addition, the specific contact resistance between the front contact and emitter was measured at various firing conditions using the transfer length model. On an emitter with the sheet resistance of 60 Ω/sq, a specific contact resistance below 5 mΩ cm² could be achieved at a peak firing temperature around 800 °C. We found that the incorporated nano‐glass frit act as a very effective fire through agent, and an abundant amount of Ag crystallites was observed along the interface glass layer. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

The 18.3% Silicon Solar Cells with Nano-Structured Surface and Rear Emitter

A nano-structured surface is formed on the pyramid structure of n-type silicon solar cells by size-controlled silver nano-particle assisted etching. Such a nano-structure creates a front average weighted reflectance of less than 2.5%in the 300-1200 nm range due to the broadband reflection suppression. The sodium hydroxide is used to obtain the low-area surface by post-etching the nano-structure, thus the severe carrier recombination associated with the nano-structured surface could be reduced. After emitter forming, screen printing and firing by means of the industrial fabrication protocol, an 18.3%-efficient nano-structured silicon solar cell with rear emitter is fabricated.The process of fabricating the solar cells matches well with industrial manufacture and shows promising prospects.     

Properties of ITO–AZO bilayer thin films prepared by magnetron sputtering for applications in thin-film silicon solar cells

In this paper we study the electro-optical behavior and the application of indium–tin oxide (ITO) and aluminum-doped zinc oxide (AZO) bilayer thin films for silicon solar cells. ITO–AZO bilayer thin films were deposited on glass substrates using radio-frequency magnetron sputtering. The experimental results show that a decrease in the electrical resistivity of the ITO–AZO bilayer thin films has been achieved without significant degradation of optical properties. In the best case the resistivity of the bilayer films reached a minimum of 5.075×10^?4 Ω?cm when the thickness of the AZO buffer layer was 12 nm. The ITO–AZO bilayer films were applied as the front electrodes of amorphous silicon solar cells and the short-circuit current density of the solar cells was considerably increased.     

Hydrogen passivation of multi—crystalline silicon solar cells

The effects of hydrogen passivation on multi-crystalline silicon (mc-Si) solar cells are reported in this paper. Hydrogen plasma was generated by means of ac glow discharge in a hydrogen atmosphere. Hydrogen passivation was carried out with three different groups of mc-Si solar cells after finishing contacts. The experimental results demonstrated that the photovoltaic performances of the solar cell samples have been improved after hydrogen plasma treatment, with a relative increase in conversion efficiency up to 10.6\%. A calculation modelling has been performed to interpret the experimental results using the model for analysis of microelectronic and photonic structures developed at Pennsylvania State University.