可见及近红外宽光谱响应的高效固态量子点敏化太阳能电池

PbS quantum dots sensitized SnO2 (TiO2) nanocrystalline thin film solar cells will be fabricated and their photoresponse to solar spectrum is wished to be expanded from the visible region to the near infrared region by adjusting the band structure of PbS quantum dots according to quantum size effect. At the same time, the band position of PbS quantum dots is needed to well match the energy band of SnO2 (TiO2) nanocrystals. The kinetic processes of photogenerated electrons in quantum dots sensitized nanocrystalline thin film including injection, transport and recombination, as well as the kinetic process of photogenerated holes presenting in the quantum dots/hole-transpporting materials interface will be studied in detail based on the selection of hole-transporting materials with a suitable HOMO position. These kinetic processes will be optimized by ions doping and microstructure designing to the nanocrystalline thin film, passivation of surface defects in quantum dots sensitized nanocrystalline thin film, selection of hole-transporting materials and their deposition method. By these hard works, the injection efficiency of photogenerated electrons, the transport speed of electrons in the nanocrystalline thin film and the transfer rate of holes will be increased, and thus the recombination of photogenerated charged carriers will be suppressed. At last, a solid state quantum dots sensitized solar cell with a structure of semiconductor nanocrystalline thin film/quantum dots/hole-transporting materials layer will be fabricated. The conversion efficiency of 4% can be attained by improving photon to current conversion efficiency due to the photoresponse expansion of the solar cell to solar spectrum and optimum of the kinetic processes mentioned above.

本项目研究PbS量子点敏化SnO2及 TiO2纳晶薄膜太阳能电池，利用量子尺寸效应调节PbS量子点的能带结构，使量子点的光谱吸收从太阳光谱的可见区扩展至近红外范围。同时使PbS量子点能带位置与SnO2、TiO2纳晶薄膜能级相互匹配。在选择能级匹配的空穴传输材料的基础上，研究量子点敏化半导体纳晶薄膜的光生电子包括注入、输运、复合和量子点与空穴传输材料之间的光生空穴转移等多步动力学过程和机制。采用纳晶薄膜的离子掺杂、微结构优化设计、钝化量子点敏化纳晶薄膜的表面缺陷和改变空穴传输材料的种类和空穴传输层制备方法等技术方法和手段，优化多步动力学过程参数，达到提高光生电子注入效率、膜内电子输运速度和空穴转移速度，减少光生电荷复合的目的。研制结构为半导体纳晶薄膜/量子点/空穴传输层的固态量子点敏化太阳能电池，在实现高效采集太阳光能和优化动力学参数的基础上，提高光电流量子效率，使光电转换效率达到4%以上。

可再生能源特别是绿色能源太阳能的开发利用成为我国可持续发展的能源战略决策。量子点敏化太阳能电池是一类成本低、有应用前景的太阳能电池，但其光电转换效率仍然低于其它种类电池，也远低于其理论值。本项目通过扩展量子点敏化太阳能电池的光谱响应范围到近红外区提高电池的光电转换效率，研究了由此引起的存在于光生电子包括注入、输运、复合和量子点与空穴传输材料之间的光生空穴转移等多步动力学过程中的问题，通过对这些动力学过程机制的分析和调控探索了提高量子点敏化纳晶薄膜太阳能电池光电性能的途径，主要取得了以下一些研究成果。根据控制量子点尺寸单分散的生长原理，首次提出制备量子点的两相溶液法，并在纳晶薄膜上现场生长了不同粒径的单分散硫化铅量子点。通过改变制备条件得到吸收峰从1500纳米到可见光区间一系列硫化铅量子点敏化纳晶薄膜，使其光响应区间从可见光扩展到近红外区间。同时，制备了二氧化锡和多种元素掺杂的二氧化钛纳晶薄膜，使掺杂二氧化钛纳晶薄膜的平带电位在本征位置的-45到200毫伏范围内可调，并能与不同粒径的硫化铅量子点的导带能级相匹配。系统研究并发展了一系列量子点敏化纳晶薄膜的表面和界面修饰技术，达到有效调控光生电子在薄膜内的多步动力学过程。采用原位化学催化聚合和电化学聚合两种现场制备空穴传输层技术改善空穴传输层与量子点敏化纳晶薄膜界面性能，从而改善空穴转移过程，有效抑制光生电荷的复合。在此基础上，制备了结构为导电玻璃/量子点敏化纳晶薄膜/空穴传输层/金属电极的固态量子点太阳能电池。结合当前研究热点，在纳晶薄膜内部引入由在惰性气体内煅烧金属有机框架薄膜形成的多孔导电碳骨架，提高量子点敏化纳晶薄膜导电性，减小光生电子与空穴的复合，使其光电转换效率达到5.8%。

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