PbS量子点超晶格太阳能电池的微观调控及其载流子产生和传输机理研究

With the advantages of high theoretical efficiency, quantum dot solar cells have become a hotspot of present research. However, the shortage of carrier diffusion length and invalid enhancement of multiple exciton generation are serious problems in the industry process of quantum dot solar cell. Superlattice structure can improve the arrangement of quantum dots in thin film, which is also benefit to the resonance coupling between quantum dots. It can be expected to reduce the distance of carrier transfer and the threshold energy of multiple exciton generation, which is the effect way to solve the problems. Here, different size, morphologies and surface ligands of quantum dots are employed to modulate the spatial structure, spatial distance, spatial dimension and spatial order of quantum dot superlattice optical absorption layer. The influences on the carrier transfer performance of quantum dot solar cell from the microstructure of superlattice will be investigated. And it will also explore the relationship between the resonance coupling enhancement of quantum dot superlattice and the efficiency of carrier generation and separation, which can realize the improvement of the carrier diffusion length of the solar cells and the effective enhancement of multiple exciton generation. Meanwhile, the dynamics process of carrier generation, transfer and recombination in quantum dot solar cell will be confirmed, which can clarify the carrier generation, transfer and recombination mechanism. Furthermore, this project will provide scientific reference and theoretical support for the investigation and development of high efficiency quantum dot solar cell.

量子点太阳能电池以极高理论效率成为当前的研究热点，其载流子扩散长度不足和多激子效应无法有效增强是量子点太阳能电池产业化进程中的难点。超晶格结构能改善薄膜内量子点的排列方式，有利于量子点之间的共振耦合，有望缩短载流子的传输距离，并降低多激子产生的阈值能量，是解决问题的有效途径。为此，本项目拟利用不同尺寸、形貌结构及表面配体的PbS量子点对量子点超晶格光吸收层的空间结构、空间距离、空间维度及空间有序度进行联合调控，研究超晶格的微观结构对量子点太阳能电池载流子传输性能的影响规律，并探索量子点超晶格内共振耦合增强与载流子产生及分离效率的内在联系，实现电池载流子扩散长度的提升及多激子效应的有效增强，同时明晰量子点超晶格太阳能电池中载流子产生、传输及复合的动力学过程，揭示载流子产生、传输及复合机理，为高效量子点太阳能电池的研究提供科学借鉴和理论支持。

量子点太阳能电池因其低成本和高理论效率的优势，成为光伏发电降本增效的关键技术。为了解决量子点太阳能电池产业化进程中载流子产生和传输的基础科学问题和技术瓶颈，本项目发展了PbS量子点的一步可控制备方法，实现了PbS量子点的尺寸和表面配体的调控；优化了量子点光吸收薄膜结构，实现了量子点太阳能电池载流子传输效率的有效提升；明晰了量子点太阳能电池载流子的产生和传输机理。结果表明：①通过调控铅和硫的前驱体，可以有效调控PbS量子点的尺寸和表面配体。通过开发一步合成法，同时实现了PbS量子点的尺寸调控和表面钝化，提升了量子点的质量和均匀性，降低了量子点的表面缺陷态密度。②通过尺寸调控和多尺寸联合的方式，实现了排列紧密有序的PbS量子点光吸收薄膜类晶格结构，降低了薄膜内部的缺陷态密度，量子点太阳能电池的光电转换效率从6.31%提升到7.58%。③采用表面配体后处理方式，改善了PbS量子点光吸收薄膜类晶格结构的均匀性和有序性，进一步钝化了薄膜内的缺陷，优化了载流子产生和传输效率，电池的光电转换效率进一步提升到8.17%。④分析了不同结构的量子点太阳能电池中载流子产生效率和载流子传输速率，明确了量子点太阳能电池的微观结构和光电性能之间内在联系，阐明了量子点太阳能电池的载流子产生和传输机理。通过本项目资助，在国内外学术期刊发表SCI论文7篇，授权国家发明专利2项；举办和参加国内外学术会议7次；培养研究生7名；指导学生获得中国可再生能源学会大学生优秀科技竞赛三等奖1项；获长沙理工大学湖湘学者拔尖人才1人。项目相关研究成果为高效量子点太阳能电池的研究和应用提供科学借鉴和理论支持。