掺硼纳米非晶硅的太阳能电池窗口层应用研究

本文通过等离子体增强化学气相沉积(PECVD)法沉积p型纳米非晶硅薄膜(na-si:H),系统地研究了掺杂气体比(B2H6/SIH4)、沉积温度、射频电源功率对薄膜结构、光学、电学性能的影响.研究表明,轻掺硼有利于非晶硅薄膜晶化,但随着掺硼量的增加,硼的"毒化"作用又使薄膜变为非晶态;与p型a_si:H相比,掺硼纳米硅薄膜的光学带隙Eopt较高,电导率较高,电导激活能较低,是一种很有潜力的太阳能电池窗口层材料.     

溶胶-凝胶法制备铜锌锡硫材料的研究进展

四元硫化物铜锌锡硫(CZTS)是一种新型薄膜太阳电池材料,具有锌黄锡矿结构,呈p型导电性,带隙约为1.5eV,光学吸收系数高于10~4cm~(-1),这些特性与太阳光谱相匹配。基于上述原因,CZTS薄膜是一种有望能低成本、可规模化开发利用的新型薄膜太阳电池材料。简要阐述了CZTS性质及其薄膜太阳能电池的器件结构,详细介绍了溶胶-凝胶方法制备CZTS薄膜及其相应器件效率的研究进展。最后,总结了此方法制备CZTS薄膜及其相关电池性能难以突破的关键技术问题,并提出了有效的改进措施,对CZTS薄膜太阳电池未来的研究进行了展望。     

硼掺杂对PECVD制备的纳米非晶硅薄膜电学行为的影响

本文采用PECVD法制备硼掺杂纳米非晶硅薄膜(na-Si:H),系统研究了掺杂气体比(B2H6/SiH4)、衬底温度Ts、RF电源功率对薄膜电学性能的影响.研究表明,与传统掺硼非品硅不同,随硼掺杂浓度的增加,掺硼na-Si:H薄膜的电导率先减小后增大并最终趋于饱和,其电导激活能E≈0.50eV、σph/σd＞102,具有应用于太阳能电池p型层的潜力.     

非晶硅/非晶硅锗叠层电池器件结构优化与制备工艺研究

非晶硅/非晶硅锗叠层电池制备中非晶硅锗子电池本征层采用"喇叭口"结构。通过优化各层掺杂浓度,实现叠层电池光学带隙从1.95~1.5 eV之间的梯次平滑过渡(其中P层窗口层带隙1.95 eV,a-Si∶H1.7eV,a-SiGe∶H1.5eV)。探讨了NP隧穿结对叠层电池开路电压(Voc)和填充因子(FF)的影响,制备出FF为0.739的a-Si∶H/a-Si Ge∶H叠层电池。调整叠层电池中子电池本征层厚度,制备出效率为9.06%的a-Si∶H/a-SiGe∶H叠层电池(未加减反射层)。     

微晶硅同质结薄膜太阳电池的数值模拟分析

采用太阳电池电容模拟软件(简称SCAPS)对p-i-n结构的微晶硅同质结薄膜太阳电池进行了数值模拟。研究了本征层的厚度和缺陷态浓度及窗口层的厚度等参数对电池性能的影响。得到的主要结论如下:(1)随着本征层缺陷态浓度Nt的增加,电池的各性能参数均单调下降。(2)随着本征层厚度的增加,长波段的光谱响应逐渐改善,但该层过厚则导致中波段的光谱响应急剧下降,在Nt=1.0×1016/cm3的条件下,本征层厚度在1.5～2.0μm范围内电池效率均可达到7.0%以上。(3)p型窗口层的厚度对短波段的光谱响应及短路电流密度JSC有较大影响。     

掺硅类金刚石薄膜的制备及其光学性质研究

利用直流磁控溅射技术在单晶硅和光学玻璃表面制备了掺硅类金刚石薄膜,采用紫外-可见光光谱仪、原子力显微镜、X射线光电子能谱(XPS),荧光光谱仪考察了不同硅含量对类金刚石薄膜的光学透过、表面形貌、电子结构和光学带隙的影响.结果表明,掺硅后的类金刚石薄膜的表面粗糙度先变大后变小,光学带隙变宽,但当掺硅达到一定量时,光学带隙有所降低.随着硅掺入量的增加,薄膜的红外透过率显著提高;光的发射中心"蓝移"并且强度增加.XPS的结果表明薄膜的sp3/sp2的比率随着硅含量的增加而变大.     

CIGS薄膜太阳能电池缓冲层材料的研究进展

CIGS薄膜太阳能电池的缓冲层为低带隙CIGS吸收层与高带隙ZnO窗口层之间形成过渡,减少两者带隙的晶格失配和带隙失调,并可防止溅射ZnO窗口层时给CIGS吸收层带来损害等,对提高CIGS薄膜太阳能电池效率起了重要作用.介绍了CIGS薄膜太阳能电池缓冲层材料的分类和制备工艺,主要阐述了CdS、ZnS及In2S3薄膜缓冲层材料及化学水浴法、原子层化学气相沉积法、金属化合物化学气相沉积法等制备工艺的研究现状,最后指出CIGS太阳能电池缓冲层在制备工艺、环境保护及大规模工业化生产中遇到的问题,并展望了其发展方向.     

三层减反射膜的模拟及其在太阳电池中的应用

使用减反射膜层是提高太阳电池短路电流密度进而提高电池转换效率的有效手段之一。针对CdTe薄膜太阳电池的光谱响应范围,基于AM1.5辐照光谱,优化设计了MgF2/H4/Al2O3结构的减反射薄膜,使用电子束蒸发技术制备了该减反射膜,使用椭圆偏振仪、紫外/可见分光光度计、原子力显微镜分别测量了所制备薄膜的光学性质和表面形貌,对比分析了膜系结构理论模拟与实验测量结果。结果表明,使用该减反射薄膜后,电池的量子效率提高了7.3%;光电转换效率从12.5%提高到13.3%。     

微晶硅渐变带隙太阳电池的模拟计算研究

运用AMPS软件结合相关实验数据,利用微晶硅带隙与材料晶相比的关系,对pin型微晶硅薄膜太阳电池i层带隙渐变结构的总光生载流子产额、载流子复合速率等参数进行了模拟,并与普通pin型微晶硅薄膜太阳电池进行了对比分析.结果表明,一方面带隙渐变结构增加了进入微晶硅i层作为活性层的光吸收;另一方面渐变各层之间存在缺陷和复合中心,影响载流子收集.对于带隙递增型微晶硅(μc-Si:H)薄膜太阳电池,当i层总厚度为1.2μm时.其光电转化效率为14.843%.     

非晶碳膜及掺氮非晶碳膜的制备及光学性质的比较

用射频磁控溅射法成功地制备了非晶碳薄膜薄膜。拉曼光谱表征表明所沉积的非晶碳薄膜是非晶结构,具有类金刚石特性。对所制备的掺氮非晶碳薄膜用光电子能谱和红外光谱进行了表征。同时还研究了两种薄膜的光学性质,为该类薄膜的实际应用提供了可靠的实验依据     

硼掺杂对非晶硅薄膜微结构和光电性能的影响

以硅烷 (SiH4 )和硼烷 (B2 H6)为气相反应先驱体 ,采用等离子体增强化学气相沉积法 (PECVD)制备出轻掺硼非晶氢硅薄膜。X射线衍射、原子力显微镜和光、暗电导测试表明 ,一定程度的硼掺杂提高了非晶氢硅薄膜的电导率 ,降低了非晶氢硅薄膜的光、暗电导比 ,并促进了非晶氢硅薄膜中硅微晶粒的生长。红外吸收谱研究预示了大量的硼原子与硅、氢原子之间能形成某些形式的复合体 ,仅有少量硼元素对P型掺杂有贡献。     

掺硼四面体非晶碳膜的微观结构及光谱表征

分别采用过滤阴极真空电弧技术制备了不同含硼量四面体非晶碳(ta-C:B)膜, 并用X射线光电子能谱(XPS)、Raman光谱对薄膜的微观结构和化学键态进行了研究. XPS分析表明薄膜中B主要以石墨结构形式存在, 随着B含量的增加, sp³杂化碳的含量逐渐减小, Ta-C:B膜的Raman谱线在含硼量较高时, 其D峰和G峰向低频区偏移, 且G峰的半峰宽变窄, 表明B的引入促进了sp²杂化碳的团簇化, 减小了原子价键之间的变形, 从而降低了薄膜的内应力．     

Amorphous silicon carbide heterojunction solar cells on p-type substrates

The performance of silicon heterojunction (SHJ) solar cells is discussed in this paper in regard to their dependence on the applied amorphous silicon layers, their thicknesses and surface morphology. The emitter system investigated in this work consists of an n-doped, hydrogenized, amorphous silicon carbide a-SiC:H(n) layer with or without a pure, hydrogenized, intrinsic, amorphous silicon a-Si:H(i) intermediate layer. All solar cells were fabricated on p-type FZ-silicon and feature a high-efficiency backside consisting of a SiO₂ passivation layer and a diffused local boron back surface field, allowing us to focus only on the effects of the front side emitter system. The highest solar cell efficiency achieved within this work is 18.5%, which is one of the highest values for SHJ-solar cells using p-type substrates. A dependence of the passivation quality on the surface morphology was only observed for solar cells including an a-Si:H(i) layer. It could be shown that the fill factor suffers from a reduction due to a reduced pseudo fill factor for emitter thicknesses below 11 nm due to a lower passivation quality and/or a higher potential for shunting thorough the a-Si emitter to the crystalline wafer with the conductive indium tin oxide layer. Furthermore, the influence of a variation of the doping gas flow (PH₃) during the plasma enhanced chemical vapor deposition of the doped amorphous silicon carbide a-SiC:H(n) on the solar cell current-voltage characteristic-parameter has been investigated. We could demonstrate that a-SiC:H(n) shows in principle the same dependence on PH₃-flow as pure a-Si:H(n).     

Effects of RF power and pressure on performance of HF-PECVD silicon thin-film solar cells

High-frequency plasma-enhanced chemical vapor deposition (HF-PECVD) is a widely applicable method of deposition over a large area at a high rate for fabricating silicon thin-film solar cells. This investigation presents the properties of hydrogenated amorphous silicon (a-Si:H) films and the preparation of highly-efficient p-i-n solar cells using an RF (27.1 MHz) excitation frequency. The influence of the power (10-40 W) and pressure (20-50 Pa) used during the deposition of absorber layers in p-i-n solar cells on the properties and mechanism of growth of the a-Si:H thin films and the solar cells is studied. The a-Si:H thin films prepared under various deposition conditions have widely varying deposition rates, optical-electronic properties and microstructures. When the deposition parameters were optimized, amorphous silicon-based thin-film silicon solar cells with efficiency of 7.6% were fabricated by HF-PECVD. These results are very encouraging for the future fabrication of highly-efficient thin-film solar cells by HF-PECVD.     

Amorphous hydrogenated silicon-nitride films for applications in solar cells

The application of anti-reflective coatings (ARC) is a good method to improve the solar cell construction. The authors developed the RF plasma enhanced chemical vapour deposition method for preparation of amorphous silicon-nitrogen (a-Si:N:H) films for potential optoelectronic applications. The films have been obtained on borosilicate glass and monocrystalline silicon (1 0 0) (Cz-Si) in a process with optimised technological parameters such as a content of gaseous mixture of silane (SiH₄) and ammonia (NH₃). The properties of samples have been investigated by optical spectroscopy (PERKIN-ELMER Lambda 19) and scanning electron microscopy (SEM). The correlation between film properties and process parameters has been found. The results of optical investigations show that these materials are characterised by a variable optical gap dependent on the nitrogen content. After deposition of a-Si:N:H, a decrease in the total reflectivity, as compared to that of monocrystalline Si, was observed. The simulation of multicrystalline silicon solar cells performance with and without the ARC was done with the use of PC1D programme. The influence of the ARC on solar cell efficiency was observed. The obtained results indicate that a-Si:N:H films are suitable for application as antireflective and protective coatings for solar cells.     

非晶金刚石薄膜的拉曼光谱研究

碳离子的能量是影响非晶金刚石薄膜结构和性质最关键的工艺参数．采用磁过滤真空溅射离子技术,研究不同衬底偏压Ｖ_ｂ（即不同碳离子能量）下制备的非晶金刚石薄膜的拉曼光谱和表面形貌．结果表明：－５０Ｖ≤Ｖ_ｂ≤－１０Ｖ时,样品表面均匀、光滑,拉曼谱是对称且很宽的散射带;Ｖ_ｂ＞－１０Ｖ或Ｖ_ｂ＜－５０Ｖ时,已有晶团出现,表面粗糙度明显增加,拉曼谱明显地分裂为１５８０ｃｍ^－１的Ｇ带和１３５０ｃｍ^－１的Ｄ带．     

非晶金刚石薄膜对温度的敏感性研究

采用过滤阴极真空电弧技术制备非晶金刚石薄膜, 在-190～600℃范围研究非晶金刚石薄膜的温度敏感性. 利用液氮泵在Linkam试验台上冷却样品并实时采样, 通过炉中退火实现样品加热. 分别测试可见光拉曼光谱和纳米压痕, 研究薄膜的微结构和机械性能的变化. 实验表明: 过滤阴极真空电弧制备的非晶金刚石薄膜具有较好的热稳定性. 在空气中退火到400℃, 其硬度和弹性模量基本保持不变, 其结构可以一直稳定到500℃, 但是到600℃, 薄膜因为氧化作用而快速消耗. 非晶金刚石薄膜的可见光拉曼光谱显示随着温度的升高, 谱峰峰位向高频偏移. 在低温冷却过程中, 薄膜对温度变化不敏感, 其结构保持不变.     

双纳米硅p层优化非晶硅太阳能电池

采用等离子体增强化学气相沉积(Plasma Enhanced Chemical Vapor Deposition,PECVD)技术在高功率密度、高反应气压和低衬底温度下制备出不同氢稀释比RH的硅薄膜.高分辨透射电镜(High-Resolution Transmission Electron Microscopy,HRT...     

Polycrystalline ZnO: B grown by LPCVD as TCO for thin film silicon solar cells

Conductive zinc oxide (ZnO) grown by low pressure chemical vapor deposition (LPCVD) technique possesses a rough surface that induces an efficient light scattering in thin film silicon (TF Si) solar cells, which makes this TCO an ideal candidate for contacting such devices. IMT-EPFL has developed an in-house LPCVD process for the deposition of nanotextured boron doped ZnO films used as rough TCO for TF Si solar cells. This paper is a general review and synthesis of the study of the electrical, optical and structural properties of the ZnO:B that has been performed at IMT-EPFL.The influence of the free carrier absorption and the grain size on the electrical and optical properties of LPCVD ZnO:B is discussed. Transport mechanisms at grain boundaries are studied. It is seen that high doping of the ZnO grains facilitates the tunnelling of the electrons through potential barriers that are located at the grain boundaries. Therefore, even if these potential barriers increase after an exposition of the film to a humid atmosphere, the heavily doped LPCVD ZnO:B layers show a remarkable stable conductivity. However, the introduction of diborane in the CVD reaction induces also a degradation of the intra-grain mobility and increases over-proportionally the optical absorption of the ZnO:B films. Hence, the necessity to finely tune the doping level of LPCVD ZnO:B films is highlighted. Finally, the next challenges to push further the optimization of LPCVD ZnO:B films for thin film silicon solar cells are discussed, as well as some remarkable record cell results achieved with LPCVD ZnO:B as front electrode.     

A simulation study of thin film tandem solar cells with a nanoplate absorber bottom cell

A tandem thin film solar cell with a nanoplate absorber bottom cell that can solve the trade-off between light absorption and carrier transport in thin film solar cell is investigated. This structure has an n-type microcrystalline silicon nanoplate array on the substrate, and the p- and i-layers are sequentially grown along the surface of each n-type microcrystalline silicon nanoplate for bottom cell. After above bottom cell is fabricated, a similar process is used to fabricate an amorphous Si p-i-n top cell. High-aspect-ratio width/height nanoplates allow for the use of a material with sufficient thickness to obtain good optical absorption while simultaneously providing short collection lengths for excited carriers perpendicular to light absorption. The power conversion efficiency of nanoplate solar cells with 15,000 nm plate height is around 10%, which is an approximately 40% enhancement over a planar solar cell with a similar layer stack.