CdSxSe1-x量子点敏化NiO光阴极制备、能级调控及界面电荷转移机制研究

The dye-sensitized solar cells (DSCs) assembled with p-type photocathode and n-type photoanode perform higher open circuit voltage and could absorb sun light over broad wavelength range. The photoelectric performance of NiO photocathode has been significantly improved due to the design and optimization of the organic dye molecular structure in recent years. Whereas, the organic dye sensitized NiO photocathode still shows much lower monochromatic incident photon-to-current conversion efficiency and short-circuit density, compared with the TiO2 photoanode. The inorganic quantum dot shows high extinction coefficients and tunable band gap which makes them particularly well-suited absorbers for NiO photocathode. In this project, we plan to co-sensitize NiO films using CdSxSe1-x quantum dots with different band gap. The band gap structure of CdSxSe1-x layer will be designed and optimized carefully according to the organic dye molecular of “Donor-Acceptor” structure. So the band gaps of CdSxSe1-x layers were not only perfectly matched with each other but also suited for NiO films. As a result, the photogenerated hole-electron pairs could be efficiently separated. The photogenerated holes could be efficiently injected into the valence band of NiO and the reaction rate constant for electron-hole recombination will be restrained. It will be thoroughly investigated about the effects of band gap structure on the photoinduced charge separation and the charge transfer at the interface of NiO/CdSxSe1-x/electrolyte. We will try to elucidate the interrelation of the band gap structure, the kinetics of photoinduced charge transfer reactions and the photoelectric conversion properties.

P型光阴极应用于染料敏化太阳能电池可拓宽吸收光谱范围，提高开路光电压。近年来，由于新型有机染料分子结构的设计与优化，p型NiO光阴极的性能取得了较大提升，但与n型TiO2光阳极相比，其单色光光电转化效率仍较低，短路光电流较小。无机量子点消光系数高，能级结构易于调控，是NiO光阴极更有潜力的敏化剂。本项目拟借鉴“Donor-Acceptor”结构有机染料分子的设计思路，设计、构建不同能级结构的CdSxSe1-x 量子点共敏化NiO薄膜，优化能级结构，使敏化层内部、敏化层与NiO薄膜之间能级相互匹配，实现光生电荷有效分离，光生空穴快速注入NiO价带，并抑制NiO价带空穴的副反应，制备高效p型NiO光阴极。研究量子点敏化层能级结构对光生电荷分离及在NiO/CdSxSe1-x/电解液界面转移过程的影响机制，阐明薄膜能级结构、光生电荷界面转移动力学及传输动力学与光电转换性能之间的相互关系。

光阴极应用于染料敏化太阳能电池可拓宽吸收光谱范围，提高开路光电压。该项目首次将CdSeS量子点引入到NiO光阴极，制备量子点敏化的p型敏化太阳能电池（p-QDSCs）。优化后，电池的短路光电流达到14.68 mA cm-2，光电转换效率达到1.02%，这比已报道的p-QDSCs的性能提高了近一个数量级。通过稳态荧光光谱及瞬态荧光谱分析，证实CdSSe量子点可以在NiO纳晶表面实现有效的光生电荷分离，并顺畅地注入到NiO价带。交流阻抗测试表明CdSSe敏化的NiO薄膜光阴极具有较大的复合反应阻抗，光生电荷具有较长的有效寿命。详细研究了聚乙二醇在NiO薄膜制备过程中的作用及其对电池光电性能的影响，发现聚乙二醇的添加可以有效减少NiO薄膜中的裂纹，增强NiO薄膜与导电玻璃基底的连接性能，避免NiO薄膜的脱落，实验制备了厚度达2.6 μm的NiO纳晶薄膜，并将优化后的NiO薄膜光阴极与CdS/CdSe量子点共敏化的TiO2光阳极组装p-n叠层量子点敏化太阳能电池，叠层电池的开路光电压要比NiO光阴极或TiO2光阳极单独组装的敏化太阳能电池均有所提高。该项目给出了一种制备短路光电流与敏化光阳极相匹配的光阴极的方法，并尝试将其与光阳极组装p-n叠层敏化太阳能电池，为p-n叠层太阳能电池的研究提供一定的理论基础及参考数据。本课题已按照研究计划完成了相关研究内容，基本达到了预期目标，在基础研究和人才培养等方面取得了一定的进展。相关研究结果已在学术期刊上发表论文4篇。申请发明专利3项，其中2项已获得授权。培养硕士研究生6名。