【作者】 李志强；

【导师】 黄素梅；

【作者基本信息】 华东师范大学 ， 纳米物理学， 2012， 博士

【摘要】 本论文针对目前薄膜太阳电池发展中存在的若干问题进行了研究,涉及铜铟镓硒、铜锌锡硫硒薄膜太阳电池和上转换材料在薄膜太阳电池中的应用两部分。对于铜铟镓硒薄膜太阳电池,在实验室已有工作基础上对制备工艺进行了进一步的优化和改进。一方面,对铜铟镓硒吸收层薄膜进行了表面修饰。在沉积铜铟镓金属预制层的同时用共溅射的方法进行了金属锌的掺杂,制备出了锌掺杂浓度为零到0.8at%的铜铟镓金属预制层。再经过硒化处理得到掺杂锌的铜铟镓硒薄膜。研究了锌的掺杂浓度对铜铟镓硒薄膜形貌及结构的影响,并把锌掺杂的铜铟镓硒薄膜制备成完整的电池器件。与未掺杂的铜铟镓硒薄膜太阳电池相比,锌掺杂浓度为0.4%时的器件效率有22%的提高。另一方面,对铜铟镓硒薄膜太阳电池结构进行了改进。制备了硫化镉/硫化铟和硫化锌/硫化铟双缓冲层结构的太阳电池,研究了双缓冲层对太阳电池性能的影响并对其机理进行了讨论。硫化铟的引入能够增强太阳电池在可见光范围内的光谱响应,对提高器件性能有着很大的作用。铜锌锡硫硒材料有较高的吸收系数,且所有元素地球含量丰富,是铜铟镓硒材料的理想替代品。本文提出了一种简单且无毒的制备铜锌锡硫硒薄膜的方法,首先把金属盐(包括醋酸铜、醋酸锌和氯化亚锡)和硫脲溶于吡啶得到前驱物溶液,再利用前驱物溶液旋涂制备成前驱物薄膜,最后经过高温硒化或硫化处理得到铜锌锡硫(硒)薄膜。本文研究了硒化或硫化处理对前驱物薄膜形貌、结构和化学构成的影响,并研究了以硒化后的铜锌锡硫硒薄膜为吸收层的太阳电池器件。另外,对于一维结构的铜锌锡硫材料,本文以已制备好的硒化铜纳米线为模板,通过加入醋酸锌和氯化亚锡利用水热反应合成出了铜锌锡硒纳米线束。这些纳米线束直径为200-400纳米长度能达到数百微米。如果在反应的同时加入少量的升华硫粉,反应生成物则为与铜锌锡硒纳米线束形貌相似的铜锌锡硒／铜锌锡硫核壳结构纳米线束。本文研究了反应溶液中硫硒元素比对生成的纳米线束的结构,形貌及光学性质的影响,并讨论了这类一维纳米线束在光伏电池中的应用前景。薄膜太阳电池对近红外区域的光几乎是不吸收的,这在一定程度上会影响器件转换效率的进一步提升,而上转换材料则能把近红外光转换为可见光被太阳电池吸收利用。本文制备了NaYF4:Yb/Er/Gd纳米棒与金纳米复合结构(金纳米颗粒和连续的金壳)的上转换材料,研究了金纳米结构对其发光性质的影响。金纳米颗粒能够使其上转换荧光强度增强3倍以上,而连续的金壳则使其荧光强度产生了淬灭。另外,本文还研究了这三种不同结构的上转换材料在非晶硅薄膜太阳电池中的应用。在980纳米激光激发下,与无上转换材料时相比,涂有纳米棒金纳米颗粒复合结构上转换材料的电池器件其短路电流有72倍的增强。得到的最大短路电流为1.16毫安,相应的量子效率为0.14%。另外,稀有金属与上转换材料的直接接触是产生上转换荧光猝灭的一个主要因素。本文通过磁控溅射在银纳米颗粒与NaYF4:Yb/Er/Gd上转换纳米薄膜之间沉积一层很薄的二氧化硅介电层,并研究了二氧化硅厚度对上转换光谱强度的影响。介电层能减少银纳米颗粒与上转换材料之间的能量转移,降低由此引起的淬灭效应。选择合适厚度的二氧化硅薄膜能使上转换荧光强度得到最大程度的增强。更多还原

【Abstract】 This thesis is composed of two parts. One part is copper indium gallium selenium (Cu(In,Ga)Se2, CIGS) and copper zinc tin sulfide selenium (Cu2ZnSn(S,Se)4, CZTSSe) thin film solar cells and the other part is NaYF4:Yb/Er/Gd upconversion nanomaterials application in thin film solar cells.For CIGS thin film solar cells. On one side, the absorber CIGS surface was modified with Zn doping using a magnetron sputtering method. CuInGa:Zn precursor films targeting a CuIn0.7Ga0.3Se2stoichiometry with increasing Zn content from0to0.8at%were prepared onto Mo-coated glass substrates via co-sputtering of Cu-Ga alloy, In and Zn targets. The CuInGa:Zn precursors were then selenized with solid Se pellets. The structures and morphologies of grown Zn doped CIGS films were found to depend on the Zn content. At zinc doping level ranging between0.2-0.6at%, the Zn doping improved the crystallinity and surface morphology of CIGS films. Compared with the performance of the nondoped CIGS cell, the fabricated CIGS solar cell displayed a relative efficiency enhancement of9-22%and the maximum enhancement was obtained at a Zn content of0.4at%. On the other side, the buffers in CIGS solar cells were modified. In based mixture Inx(OH,S)y buffer layers were deposited by chemical bath deposition (CBD) technique as an alternative to the traditional cadmium sulfide buffer layer. We investigated the absorber/buffer interface between the chalcopyrite CIGS absorber and CdS or ZnS buffer with an addition of a thin In based mixture layer. It is shown that the presence of thin Inx(OH,S)y at the CIGS absorber/CdS or ZnS buffer interfaces greatly improve the solar cell performances. The performances of CIGS cells using dual buffer layers composed of Inx(OH,S)y/CdS or Inx(OH,S)y/ZnS increased by22.4%and51.6%, as compared to the single and standard CdS or ZnS buffered cells, respectively.Copper zinc tin sulfide (CZTS) is a promising alternative to semiconductors based on gallium or indium as solar absorber material. CZTS consists of abundant and cheap elements and in addition it displays very beneficial properties like a high optical absorption coefficient and an ideal band gap for photovoltaic applications. Thin films of CZTSSe absorber layer was prepared by a nonvacuum spin coating and a subsequent selenization of precursor solutions of metal salts (Cu(CH3COO)2, Zn(CH3COO)2, SnCl2)and thiourea dissolved in pyridine. The morphological, optical properties, structural properties and element composition of each spin-coated and selenized (sulfrized) films were investigated. In addition, large-scale quaternary CZTSe as well as CZTSe/CZTS core/shell nanowires were prepared by using CuSe nanowire bundles as self-sacrificial templates. CZTSe nanowires were prepared by reacting CuSe nanowire bundles with Zn(CH3COO)2and SnCl2in triethylene glycol. X-ray diffraction (XRD) and selected area electron diffraction studies show that stannite CZTSe is formed. The formed CZTSe nanowire bundles are with diameters of200-400nm and lengths up to hundreds of micrometers. CZTSe/CZTS nanocable bundles with similar morphologies were grown by addition of some elemental sulfur to the reaction system for growth of CZTSe bundles. The stannite CZTSe/kesterite CZTS core/shell structure of the grown nanocables was confirmed by XRD and high-resolution transmission electron microscope investigation. The influence of S/Se molar ratio in the reaction system on the crystallographic structures and optical properties of CZTSe/CZTS nanocables was studied. The obtained CZTSe/CZTS core/shell nanocable bundles show broad and enhanced optical absorption over the visible and near-infrared region, which is promising for the use in photovoltaic applications.Near-infrared (NIR) to visible up-conversion (UC) NaYF4:Yb/Er/Gd nanorods in combination with gold nanostructures were prepared and applied to flexible amorphous silicon solar cells. The attachment of Au nanoparticles onto NaYF4:Yb/Er/Gd nanorods resulted in a more than three-fold increase in UC emissions, while the formation of continuous and compact Au shells around the nanorods suppressed the emissions. The related interaction mechanisms of UC emission of NaYF4:Yb/Er/Gd nanorods with plasmon modes in Au nanostructures are analyzed and discussed. Photocurrent-voltage result demonstrated that UC of NIR light led to a16-fold to72-fold improvement of the short-circuit current under980nm illumination compared with a cell without upconverters. A maximum current of1.16mA and quantum efficiency of0.14%were obtained for the cell using UC nanorods coated with Au nanoparticles under the980nm laser illumination.The UC photoluminescence in a Ag nanoparticles/SiO2/NaYF4:Yb/Er/Gd film sandwich structure were investigated. The influence of SiO2thickness on the UC emission intensity was also studied. Intensity of both green emission around540nm and red emission around660Cnm are increased obviously compared to reference of the UC film without Ag nanoparticles coverage. The thin SiO2film reduced the energy transfer between Ag nanoparticles and NaYF4:Yb, Er, Gd UC film, and surface plasmon resonance enhancement effect is dominant in this structure. Time-resolved photoluminescence spectroscopy reveals that the fluorescence lifetimes were reduced both for green and red emission. Photoluminescence spectroscopy and excitation power studies showed that Ag nanoparticles can also modify the UC process in this sandwich structure.更多还原