预先合成量子点组装制备高效量子点太阳电池

量子点太阳电池现已成为极具潜力的“第三代” 光伏器件, 其优点体现在材料成本低廉, 制备工艺简便, 以及其敏化剂特有的多激子效应(MEG) 潜能和吸光范围可方便调节等方面. 但是与染料分子敏化剂相比, 量子点敏化剂粒径更大、表面缺乏具有与TiO₂结合的官能团, 这导致其在TiO₂介孔中渗透阻力大、难以在TiO₂表面吸附沉积, 所以量子点沉积手段在电池组装过程中尤为重要. 本文综述了电池组装过程中量子点的沉积方法, 分类阐述了直接生长量子点方法: 化学浴沉积(CBD)和连续离子层吸附生长(SILAR), 以及采用预先合成量子点的沉积方法: 连接分子辅助法(LA)、直接吸附法(DA)和电泳沉积(EPD)方法, 陈述了各沉积方法的发展过程及相应电池性能的改善, 对比了这些沉积方法的优缺点. 突出介绍了预先合成量子点的沉积方法, 特别是近年来不断优化而凸显优势的连接分子辅助法(LA). 总结了此方法快速、均匀沉积以及实现器件高性能的特点, 介绍了此方法沉积表面缺陷更少、结构更完善、材料更“绿色化”的量子点敏化剂的最新研究成果.

Pre-synthesized quantum dot deposition approach to obtain high efficient quantum dot solar cells

Quantum dot sensitized solar cells (QDSCs) appear to be one of the promising photovoltaic candidates, due to the lower cost of obtaining materials and assembling processes, as well as the advantages of their QD sensitizers which exhibit properties of tailoring the absorbance spectrum to near-infrared (NIR) regions, the multiple exciton generation (MEG), hot electron extraction, etc. However, the difficulty of QDs penetrating into TiO₂ mesoporous film remains to be an obstacle for the development of QDSCs, which comes from (1) their larger size (1-10 nm) compared with dye molecules, (2) steric hindrance from the long chain organic ligands on the surface, and (3) the lack of terminal functional group of the ligand with affinity to TiO₂. These issues imply the importance of implementing an efficient QD deposition method in the fabrication process. Based on summarizing the advantages and shortcomings, this review demonstrates the development of the QD deposition approaches in direct growth deposition methods: the chemical bath deposition (CBD) method, the successive ionic layer adsorption and reaction (SILAR) method, and the pre-synthesized QD deposition methods: linker-assisted deposition (LA), direct absorption (DA) and electrophoretic deposition (EPD). As an overall comparison to be taken for all these deposition approaches, the pre-synthesized QD deposition method has outperformed the direct growth deposition method due to the use of pre-synthesized high quality QD sensitizers for better performance in surface chemistry. Especially, the LA approach in this method exhibits its excellence of fast and uniform QD deposition with high coverage, as well as in building high efficiency QDSC devices. Specifically, the improved structure of the sensitizers such as the inverted type-I, type-II core/shell structures and alloyed configuration through surface ion-exchange, has been employed to boost the charge injection and depress the charge recombination, benefited from LA pre-synthesized QDs deposition method. The advantages of the LA method are fully illustrated by the examples of the most recent work in the achievement of reaching the record efficiency of QDSCs. Finally, outlooks have been given on possible approaches to realize further improvement of fabricating the QDSCs with excellent performance at higher levels.