a-Si:H/c-Si 异质结太阳电池 J-V 曲线的 S-Shape 现象

通过异质结界面分析与 AMPS 模拟计算研究了 a-Si:H/c-Si 异质结太阳电池在低温工作、a-Si:H 层低掺杂、高价带补偿以及高界面态时光态 J-V 曲线出现 S-Shape 现象的物理过程,总结了 S-Shape 现象的物理原因.分析结果表明,当空穴输运受到界面势垒的限制时,空穴在 c-Si 界面附近聚集,能带重新分配,c-Si 耗尽区的电场减小,更多的电子从 c-Si 准中性区反转至 c-Si 界面及耗尽区与空穴复合,复合速率显著增大,光电流的损失显著增大,光态 J-V< 关键词： 模拟 异质结太阳电池 a-Si:H/c-Si 异质结     

钙钛矿/硅叠层太阳电池中平面a-Si:H/c-Si异质结底电池的钝化优化及性能提高

最近,旋涂法制备的钙钛矿/平面硅异质结高效叠层太阳电池引起人们广泛关注,主要原因是相比于绒面硅衬底制备的钙钛矿/硅叠层太阳电池,其制备工艺简单、制备成本低且效率高.对于平面a-Si:H/c-Si异质结电池, a-Si:H/c-Si界面的良好钝化是获得高转换效率的关键,进而决定了钙钛矿/硅异质结叠层太阳电池的性能.本文主要从硅片表面处理、a-Si:H钝化层和P型发射极等方面展开研究,通过对硅片表面的氢氟酸(HF)浸泡时间和氢等离子体预处理气体流量、a-Si:H钝化层沉积参数、钝化层与P型发射极(I/P)界面富氢等离子体处理的综合调控,获得了相应的优化工艺参数.对比研究了p-a-Si:H和p-nc-Si:H两种缓冲层材料对I/P界面的影响,其中高电导、宽带隙的p-nc-Si:H缓冲层既能够降低I/P界面的缺陷态,又可以增强P型发射层的暗电导率,提高了前表面场效应钝化效果.通过上述优化,制备出最佳的P-type emitter layer/aSi:H(i)/c-Si/a-Si:H(i)/N-type layer (inip)结构样品的少子寿命与implied-Voc分别达到2855μs和709 mV,表现出良好的钝化效果.应用于平面a-Si:H/c-Si异质结太阳电池,转换效率达到18.76%,其中开路电压达到681.5 mV,相对于未优化的电池提升了34.3 mV.将上述平面a-Si:H/c-Si异质结太阳电池作为底电池,对应的钙钛矿/硅异质结叠层太阳电池的开路电压达到1780 mV,转换效率达到21.24%,证明了上述工艺优化能够有效地改善叠层太阳电池中的硅异质结底电池的钝化及电池性能.     

双面HIT太阳电池TCO与非晶硅界面势垒的模拟优化

采用美国滨州大学研发的AMPS-1D软件,模拟了TCO与非晶硅界面势垒对TCO/a-Si:H(p+)/a-Si:H(i)/c-Si(n) /a-Si:H(i) /a-Si:H(n+) /TCO双面HIT异质结太阳电池光伏特性的影响。结果表明太阳电池的TCO/p+前接触界面势垒（对于电子）越高,越易形成欧姆接触,且电池的短波响应增强,使电池性能变好。模拟还发现,n+ /TCO背接触界面势垒（对于电子）越低,电池性能越好。若背场重掺杂,在背接触势垒小于等于0.5ev时,电池的转换效率不会受到背接触势垒的影响;若背场低掺杂,在背接触势垒很小的情况下,也能达到与重掺杂相同的转换效率。     

非晶硅太阳电池结构模拟设计

为了从理论上分析提高非晶硅太阳能电池的转化效率,运用微电子和光子结构分析一维器件模拟程序模拟非晶硅太阳电池a-SiC:H/a-Si:H/a-Si:H结构,分析比较了不同前端接触透明导电层的功函数ΦITO、禁带宽度、本征层厚度、掺杂浓度、缺陷态密度等因素对太阳电池性能的影响.模拟得到,在功函数达到5.1 eV,禁带宽度1...     

a-Si:H和a-SiNx:H薄膜中的缺陷以及载流子的非辐射复合

应用红外光谱仪、分光光度计、光声谱仪和正电子湮没寿命谱仪,从不同的角度,研究a-Si:H和a-SiN_x:H薄膜中的成分、缺陷以及光生载流子的非辐射复合。 关键词：     

PECVD分层结构对提高氢化非晶硅TFT迁移率的影响

为了进一步提高氢化非晶硅薄膜晶体管 (a-Si:H TFT) 的场效应电子迁移率, 研究了批量生产条件下对欧姆接触层和栅极绝缘层进行多层 制备, 不同的工艺参数对a-Si:H TFT场效应电子迁移率的影响. 研究表明随着对欧姆接触层 (n⁺层) 分层数的增加, 以及低速生长的栅极绝缘层 (GL层) 和高速生长的栅极绝缘层 (GH 层) 厚度比值提高, a-Si:H TFT的场效应迁移率得到提升. 当n⁺层分层数达到 3层, GL层和GH层厚度比值为4:11 时, 器件的场效应电子迁移率达到0.66 cm²/V·s, 比传统工艺提高了约一倍, 显著改善了a-Si:H TFT 的电学特性, 并在量产线上得到了验证. 关键词： 非晶硅薄膜晶体管 电子迁移率 欧姆接触层 栅极绝缘层     

非晶硅太阳电池的X射线辐照效应及其低能域光电流光谱观测

本文叙述氢化非晶硅(a-Si:H以下简称非晶硅或a-Si)太阳电池经不同剂量的X射线辐照后光电转换性能的变化情况,还用低能域(入射光子能量hv小于非晶硅光学能隙)光电流光谱法观测了经X射线辐照后,非晶硅太阳电池中局域能级的增加状况,为非晶硅太阳电池将来在航天技术中的应用提供实验数据,实验表明,X射线的辐照效应比可见光强得多,故它可以用来快速鉴定各种非晶硅太阳电池的长期稳定性。 关键词：     

异质结太阳电池中非晶钝化层的分光椭偏分析

采用分光椭偏(SE)测试技术研究晶体硅(c-Si)异质结太阳电池用氢化非晶硅(a-Si:H)薄膜钝化层的性能。采用有效媒介理论为基础进行分层多相拟合,研究了a-Si:H/c-Si界面层内部的缺陷散射周期(St)、a-Si:H体内孔隙率以及薄膜介电函数峰值随基底温度的变化规律。通过与傅里叶红外转换光谱计算得到的微结构数据对比,发现界面层的St与薄膜内部Si H和Si H2含量相关。依据高分辨率透射电镜(TEM)下呈现的形貌特征、有效少子寿命和异质结的implied开路电压等参数的辅助证明,确定SE技术作为一种有效的光学表征手段,能准确快速地判断a-Si:H对c-Si表面的钝化性能,继而定量给出适合晶体硅异质结太阳电池高质量a-Si:H钝化层生长的最优参数。     

双面HIT太阳电池TCO与非晶硅界面势垒的模拟优化

采用美国滨州大学研发的AMPS-1D软件,模拟了TCO与非晶硅界面势垒对TCO/a-Si:H(p+)/a-Si:H(i)/c-Si(n)/a-Si:H(i) /a-Si:H(n+)/TCO双面HIT异质结太阳电池光伏特性的影响.结果表明太阳电池的TCO/p+前接触界面势垒(对于电子)越高,越易形成欧姆接触,且电池的短波响应增强,使电池性能变好.模拟还发现,n+/TCO背接触界面势垒(对于电子)越低,电池性能越好.若背场重掺杂,在背接触势垒小于等于0.5 eV时,电池的转换效率不会受到背接触势垒的影响;若背场低掺杂,在背接触势垒很小的情况下,也能达到与重掺杂相同的转换效率.     

a-Si:H/a-SiNx:H超晶格薄膜的光学性质

本文介绍,当a-SiN_x:H层的厚度一定,a-Si:H层的厚度不同时,a-Si:H/a-SiN_x:H超晶格薄膜的光吸收系数、光学禁带宽度以及折射率随之变化的规律。 关键词：     

The p recombination layer in tunnel junctions for micromorph tandem solar cells

A new tunnel recombination junction is fabricated for n–i–p type micromorph tandem solar cells. We insert a thin heavily doped hydrogenated amorphous silicon (a-Si:H) p + recombination layer between the n a-Si:H and the p hydrogenated nanocrystalline silicon (nc-Si:H) layers to improve the performance of the n–i–p tandem solar cells. The effects of the boron doping gas ratio and the deposition time of the p-a-Si:H recombination layer on the tunnel recombination junctions have been investigated. The current-voltage characteristic of the tunnel recombination junction shows a nearly ohmic characteristic, and the resistance of the tunnel recombination junction can be as low as 1.5 ·cm 2 by using the optimized p-a-Si:H recombination layer. We obtain tandem solar cells with open circuit voltage V oc = 1.4 V, which is nearly the sum of the V oc s of the two corresponding single cells, indicating no V oc losses at the tunnel recombination junction.     

Effect of emitter layer doping concentration on the performance of silicon thin film heterojunction solar cell

A novel type of n/i/i/p heterojunction solar cell with a-Si:H(15 nm)/a-Si:H(10 nm)/ epitaxial c-Si(47 μm)/epitaxial c-Si(3 μm) structure is fabricated by using the layer transfer technique, and the emitter layer is deposited by hot-wire chemical vapour deposition. The effect of the doping concentration of emitter layer S_d (S_d=PH₃/(PH₃+SiH₄+H₂)) on the performance of the solar cell is studied by means of current density-voltage and external quantum efficiency. The results show that the conversion efficiency of the solar cell first increases to a maximum value and then decreases with S_d increasing from 0.1% to 0.4%. The best performance of the solar cell is obtained at S_d = 0.2% with an open circuit voltage of 534 mV, a short circuit current density of 23.35 mA/cm², a fill factor of 63.3%, and a conversion efficiency of 7.9%.     

The study of a new n/p tunnel recombination junction and its application in a-Si：H/μc-Si：H tandem solar cells

This paper reports that a double N layer (a-Si:H/μc-Si:H) is used to substitute the single microcrystalline silicon n layer (n-μc-Si:H) in n/p tunnel recombination junction between subcells in a-Si:H/μc-Si:H tandem solar cells. The electrical transport and optical properties of these tunnel recombination junctions are investigated by current-voltage measurement and transmission measurement. The new n/p tunnel recombination junction shows a better ohmic contact. In addition, the n/p interface is exposed to the air to examine the effect of oxidation on the tunnel recombination junction performance. The open circuit voltage and FF of a-Si:H/μc-Si:H tandem solar cell are all improved and the current leakage of the subcells can be effectively prevented efficiently when the new n/p junction is implemented as tunnel recombination junction.     

非晶硅界面缓冲层对非晶硅锗电池性能的影响

针对非晶硅锗电池本征层高锗含量时界面带隙失配以及高界面缺陷密度造成电池开路电压和填充因子下降的问题,通过在PI界面插入具有合适带隙的非晶硅缓冲层,不仅有效缓和了带隙失配,降低界面复合,同时也通过降低界面缺陷密度改善内建电场分布,从而提高了电池的收集效率. 进一步引入IN界面缓冲层以及对非晶硅锗本征层进行能带梯度设计,在仅采用Al背电极时,单结非晶硅锗电池转换效率达8.72%. 关键词： 非晶硅缓冲层 非晶硅锗薄膜太阳电池 带隙 界面     

Electric-field-enhanced metal-induced crystallization of hydrogenated amorphous silicon at room temperature

A novel simple method of crystallization of hydrogenated amorphous silicon (a-Si:H) thin films is described. Namely, we studied a metal-induced crystallization enhanced by a dc electric field in sandwich p⁺–i–n⁺structures. The samples were fabricated from wide-bandgap a-Si:H with high hydrogen content (13–51 at. % H). Macroscopic islands of a-Si:H (up to ∼1 mm in diameter) in the region between upper (CrNi) and lower (ITO) contacts crystallize instantaneously when a sufficiently high dc electric field (≳10⁵ V cm^-1) is applied. The crystallization sets in at room temperature and ambient atmosphere and is spatially selective. A proposed microscopic mechanism of such an easy macroscopic crystallization consists in easy diffusion of Ni and/or Ni silicides (representing nucleation sites) through a dense network of voids in hydrogen-rich a-Si:H. Received: 30 November 2000 / Accepted: 3 May 2001 / Published online: 27 June 2001     

Understanding of a-Si:H(p)/c-Si(n) heterojunction solar cell through analysis of cells with point-contacted p/n junction

We fabricated point-contacted a-Si:H(p)/c-Si(n) heterojunction solar cells using patterned SiO₂ and investigated their electrical properties using the light current–voltage (I–V) curve and Suns-V_oc measurements. The light I–V curves showed bias-dependent changes according to the applied voltage in the point-contacted cells, especially in the samples with a long distance between the point-contacted junctions. The Suns-V_oc measurements showed that the bias-dependence of the light I–V curves did not originate from the recombination in the SiO₂/Si or a-Si:H(p)/c-Si(n) interface, but from the series resistances. It is possible to explain the bias-dependent light I–V curve in terms of the conductivity of a-Si:H(p) and difference in the electrical contact properties between a-Si:H(p), ZnO and c-Si(n). These results mean that the electrical properties of the a-Si:H(p) layer and the contact properties with this layer are also critical to obtain a high J_sc and fill factor in n-type based Si heterojunction solar cells.     

a-Si ∶H/SiO2多量子阱材料制备及其光学性能和微结构研究

利用等离子体增强化学气相沉积技术制备了a-Si ∶H/SiO₂多量子阱结构材料.对a-Si ∶H/SiO₂多量子阱样品分别进行了3种不同的热处理,其中样品经1100 ℃高温退火可获得尺寸可控的nc-Si:H/SiO₂量子点超晶格结构,其尺寸与非晶硅子层厚度相当.比较了a-Si ∶H/SiO₂多量子阱材料与相同制备工艺条件下a-Si ∶H材料的吸收系数,在紫外/可见短波段前者的吸收系数明显增大,光学吸收边蓝移,说明该材料 关键词： 多量子阱 量子限制效应 光学吸收 能带结构     

后退火增强氢化非晶硅钝化效果的研究

在本征氢化非晶硅(a-Si:H(i))/晶体硅(c-Si)/a-Si:H(i)异质结构上溅射ITO时, 发现后退火可大幅增加ITO/a-Si:H(i)/c-Si/a-Si:H(i)的少子寿命(从1.7 ms到4 ms). 这一增强效应可能的三个原因是: ITO/a-Si:H(i)界面场效应作用、退火形成的表面反应层影响以及退火对a-Si:H(i)材料本身的优化, 但本文研究结果表明少子寿命增强效应与ITO和表面反应层无关; 对不同沉积温度制备的a-Si:H(i)/c-Si/a-Si:H(i)异质结后退火的研究表明: 较低的沉积温度(<175 ℃)后退火增强效应显著, 而较高的沉积温度(>200 ℃)后退火增强效应不明显, 可以确定“低温长高温后退火”是获得高质量钝化效果的一种有效方式; 采用傅里叶红外吸收谱(FTIR)研究不同沉积温度退火前后a-Si:H(i)材料本身的化学键构造, 发现退火后异质结少子寿命大幅提升是由于a-Si:H(i)材料本身的结构优化造成的, 其深层次的本质是通过材料的生长温度和退火温度的优化匹配来控制包括H含量、H键合情况以及Si原子无序性程度等微观因素主导作用的一种竞争性平衡, 对这一平衡点的最佳控制是少子寿命大幅提升的本质原因.     

Wet-chemical passivation of atomically flat and structured silicon substrates for solar cell application

Special sequences of wet-chemical oxidation and etching steps were optimised with respect to the etching behaviour of differently oriented silicon to prepare very smooth silicon interfaces with excellent electronic properties on mono- and poly-crystalline substrates. Surface photovoltage (SPV) and photoluminescence (PL) measurements, atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations were utilised to develop wet-chemical smoothing procedures for atomically flat and structured surfaces, respectively. Hydrogen-termination as well as passivation by wet-chemical oxides were used to inhibit surface contamination and native oxidation during the technological processing. Compared to conventional pre-treatments, significantly lower micro-roughness and densities of surface states were achieved on mono-crystalline Si(100), on evenly distributed atomic steps, such as on vicinal Si(111), on silicon wafers with randomly distributed upside pyramids, and on poly-crystalline EFG (Edge-defined Film-fed-Growth) silicon substrates.The recombination loss at a-Si:H/c-Si interfaces prepared on c-Si substrates with randomly distributed upside pyramids was markedly reduced by an optimised wet-chemical smoothing procedure, as determined by PL measurements. For amorphous-crystalline hetero-junction solar cells (ZnO/a-Si:H(n)/c-Si(p)/Al) with textured c-Si substrates the smoothening procedure results in a significant increase of short circuit current I_sc, fill factor and efficiency η. The scatter in the cell parameters for measurements on different cells is much narrower, as compared to conventional pre-treatments, indicating more well-defined and reproducible surface conditions prior to a-Si:H emitter deposition and/or a higher stability of the c-Si surface against variations in the a-Si:H deposition conditions.