【作者】 孙志霞；

【导师】 许林；

【作者基本信息】 东北师范大学 ， 无机化学， 2013， 博士

【摘要】 为了解决能源危机问题，太阳能的开发和利用已经成为世界范围内的研究热点。其中，提高半导体材料的光电转换效率是一个重要的研究课题。多金属氧酸盐（多酸），是一种良好的电子接受体，能够捕获半导体材料中的光生电子，从而减小半导体中载流子的复合，以提高其光电转换效率。本文以多酸为修饰组分，制备了各种半导体/多酸复合膜材料，并考察了它们的光电转换性能。具体如下：1．利用交替沉积自组装技术将PW₁₂和TiO₂制备成纳米复合膜，并用紫外可见光谱、红外光谱和原子力显微镜表征。光电流测试表明，PW₁₂/TiO₂膜的光电流响应强度与膜的层数有关。另外，与单独TiO₂膜相比，PW₁₂/TiO₂复合膜展示了更高的光电流响应和对甲醇的光电催化能力，并且PW₁₂/TiO₂膜的能量转换效率比单独TiO₂膜的能量转换效率提高了50%。2．采用交替沉积自组装技术将P₂W₁₈和聚烯丙基胺盐酸盐修饰的CdS（CdS-PAH）制备成纳米复合膜。与单独的CdS-PAH膜相比，CdS-PAH/P₂W₁₈复合膜的光电流响应强度和能量转换效率都提高了约1.5倍。这表明，多酸扮演了一个有效的电子接受体，减小了CdS中光生电子-空穴对的复合，从而提高了CdS的光电性能。我们通过荧光和表面光电压测试进一步证明了这个机理。3．使用交替沉积自组装技术将SiMo₁₂和CuPc制备成纳米复合膜。在全光和可见光的照射下，CuPc/SiMo₁₂膜都展示了比单独CuPc膜更高的光电流响应。并且，与CuPc薄膜相比，SiMo₁₂/CuPc复合膜的能量转换效率提高了约8.7倍。表面光电压测试表明，CuPc和SiMo₁₂之间发生了有效的光生电荷转移。另外，CuPc/SiMo₁₂复合膜对水合肼展示了很好的光电催化性能。4．制备了多酸(PW₁₂、P₂W₁₈)/TiO₂复合膜并组装成光电池。通过光电流、I-V曲线、电化学阻抗谱和开路光电压测试分析了不同的种类和含量的多酸/TiO₂复合膜的光电性能、电子转移和复合性质。在TiO₂中加入少量的多酸时（0.75%），显示了比单独TiO₂膜更高的光电流响应，并且PW₁₂（0.75%）/TiO₂膜和P₂W₁₈（0.75%）/TiO₂膜的能量转换效率分别是TiO₂膜的2.6倍和1.6倍。电化学阻抗谱表明，多酸的引入降低了TiO₂中载流子的复合，增加了载流子的转移，以至提高了TiO₂的能量转换效率。而在TiO₂膜中引入过量的多酸（7.5%），多酸则变成了电子陷阱填充位点，从而降低了光电性能。5．制备了以TiO₂和PW₁₂/TiO₂为光阳极的染料敏化太阳能电池。与TiO₂光阳极相比，0.75%-PW₁₂/TiO₂复合光阳极的能量转换效率提高了33%，而7.5%-PW₁₂/TiO₂光阳极的能量转换效率却降低了。这主要是因为：（1）0.75%-PW₁₂/TiO₂复合膜能够吸附更多的染料；（2）多酸的引入减小了光生载流子的复合，提高了载流子的转移。而7.5%-PW₁₂/TiO₂光阳极中，可能形成了电子陷阱填充位点，降低了光电性能。更多还原

【Abstract】 The utilization of solar energy has become a hotspot in the world to solve the shortage offossil energy. Among them, an important research topic is to improve light-to-electricityconversion efficiency of the semiconductor materials. Polyoxometalates （POMs） are a kind ofgood electron acceptors. They can transport photogenerated electrons in the semiconductors,which reduces the electron-hole recombination and then improves the photovoltaic response.In this paper, we prepared a series of semiconductors/POMs composite films and investigatedtheir photovoltaic performances.1. We fabricated the nanocomposite films of PW₁₂and TiO₂by the layer-by-layer （LbL）self-assembly method. These films were characterized by UV-vis spectroscopy, IR spectra,and atomic force microscopy. Photocurrent measurements suggested that the photocurrentresponse of the PW₁₂/TiO₂composite film was highly dependent on the deposited number oflayers. Furthermore, the PW₁₂/TiO₂composite film demonstrated the higher photocurrent andphotoelectrooxidation activity for methanol than the TiO₂film, and the power conversionefficiency of the PW₁₂/TiO₂film was improved by50%.2. We prepared the composite thin films of P₂W₁₈andpoly（allylaminehydrochloride）-modified CdS （CdS-PAH） by the LbL self-assembly method.The CdS-PAH/P₂W₁₈composite film displayed a ca.1.5-fold increase in the photocurrentresponse and power conversion efficiency, as compared to the single CdS-PAH film. Thisindicated that P₂W₁₈could act as electron acceptors to efficiently suppress electron holerecombination in CdS and improve the photovoltaic performance. Such a mechanism wasfurther proven by experimental data of fluorescence emission spectra and surfacephotovoltage spectroscopy.3. A composite film containing CuPc and SiMo₁₂was fabricated by the LbLself-assembly method. Under both solar light and visible light irradiation, the photocurrentresponse of the CuPc/SiMo₁₂film was markedly enhanced in comparison with those of theCuPc/PSS film, and the CuPc/SiMo₁₂film displayed a ca.8.7-fold increase in the powerconversion efficiency. Surface photovoltage measurements indicated that the photoinducedelectron transfer occurred between CuPc and POMs. Furthermore, the CuPc/POMs compositefilm exhibited good photoelectrocatalytic performance for the oxidation of hydrazine.4. We prepared the POMs(PW₁₂、P₂W₁₈)/TiO₂composite films and assembled the cells.We study on the photoelectrochemical performance, the electron transport and electron–holerecombination of the different content and type POMs in TiO₂film by measurements ofelectrochemical impedance spectroscopy （EIS）, photocurrent responses and I–V curves. ThePOMs/TiO₂films at low POMs loadings （0.75%） displayed the enhanced photovoltaicperformance. The power conversion efficiency of PW₁₂（0.75%）/TiO₂film andP₂W₁₈（0.75%）/TiO₂film was2.6times and1.6times that of TiO₂film, respectively. EISmeasurements proved that introducing POMs into TiO₂film could reduce electron-holerecombination and facilitate photogenerated electron transfer, which enhanced the light-to-electricity conversion efficiency. However, the excessive content （7.5%） of POMscould almost cause a negative effect on photovoltaic performance due to electron trap fillingsites.5. We fabricated the DSSCs based on both the only TiO₂photoanode and the PW₁₂/TiO₂photoanode. Compared to the TiO₂photoanode, the power conversion efficiency of0.75%-PW₁₂/TiO₂photoanode was improved by33%, while the7.5%-PW₁₂/TiO₂photoanodecould cause a negative effect on photovoltaic performance. The reasons were as follows:（1）the0.75%-PW₁₂/TiO₂film could adsord more dye;（2） The incorporating of PW₁₂into TiO₂photoanode could reduce electron-hole recombination and improve electron transfer. However,electron trap filling sites were present in the7.5%-PW₁₂/TiO₂photoanode.更多还原