PbS量子点的带隙宽谱可调、可溶液成膜等优势使其成为近红外区太阳能光电转换的关键材料。但是近红外响应型PbS量子点的大比例、非极性（100）暴露晶面缺乏稳定的表面配体，致使量子点薄膜的微结构和缺陷态难以控制，严重影响量子点太阳能电池性能提升。针对这一关键问题，本项目提出基于PbS量子点（100）暴露晶面保护策略制备低缺陷密度量子点光活性层及高效近红外响应型太阳能电池的研究构想。通过在近红外PbS量子点（100）暴露晶面液相外延生长卤化物超薄保护层，优化相转移过程中量子点表面电离配体层提升其稳定性，原子层沉积惰性氧化物后包覆量子点薄膜等手段制备低缺陷密度的PbS量子点光活性层。深入考察非极性面保护方法对器件载流子输运、注入、复合等过程的影响，优化器件制备工艺，获得阈值波长长于1400nm的高效量子点太阳能电池，推进近红外太阳能光电转换的研究进程。

Lead sulfide quantum dots (PbS QDs) have been recognized as key materials for near-infrared (NIR) photo-to-electric conversion due to their merits such as tunable bandgap in the broad spectral range from IR to visible, and solution-based film-forming technology. However, the NIR responsive PbS QDs contain a large proportion of nonpolar (100) exposed facet, interacting weakly with surface ligands, which makes the QDs easy to be oxidized and form aggregate in solution, and in turn renders a poor control over the microstructure and defects of QD film and the relatively low power conversion efficiency of NIR-QD solar cells. Being about to tackle this critical issue, we propose in the present project a strategy of rational protecting the nonpolar (100) exposed facet of NIR responsive PbS QDs for the purpose of obtaining QD photoactive layer with low defect density and fabricating NIR QD solar cell with high efficiency. The main research contents include: 1) exploring liquid-epitaxy methods to grow ultrathin protection layer of metal halides on the nonpolar (100) exposed facets of PbS QDs; 2) exploring recipes to optimize the composition of ionized surface ligand layer during phase transfer process for stable QD ink; 3) exploring the conditions of atomic layer deposition to post-encapsulate PbS QD films with inert oxides for lowering the defect density of QD film further; 4) investigating the influence of the above processing procedures on the physics of QD solar cell including the behavior of carrier transportation, injection and recombination, and optimizing the fabrication technology of QD solar cell based on the above investigation to obtain high-efficiency QD solar cell with threshold wavelength longer than 1400 nm. The above research will advance the knowledge of science community on NIR responsive QD photovoltaic materials, and impact positively on the research and development of NIR solar cells.