具有最优光学带隙的锡铅共掺型卤化物钙钛矿太阳电池的研究

The optical bandgap of the conventional lead-based perovskite is around 1.5 eV. Although its efficiency has reached 22.7%, it is not the most suitable band gap for photovoltaic semiconductors according to shockley-Queisserd theory. The absorption loss of near-infrared photon, makes the SQ limit efficiency of this semiconductors only 30%. while a large number of lead in this perovskite material also raises the environmental concerns. In response to these problems, we propose to construct a new type of perovskite by tin-lead co-doping method. By adjusting the ratio of tin and lead, the optimal optical bandgap (1.2-1.3eV) can be obtained and the SQ limit efficiency can reach the maximized value of 33%..The project will study the energy level regulation principle, film morphology and photophysical properties of this type of tin-lead mixed perovskite, build a new tin-lead mixed perovskite solar cell with the best optical bandgap. We will establish the structure-property relationship of this new perovskite semiconductor system, understand how material properties and device structure influence the charge separation, transport, and collection. Besides, we will clarify the physical mechanisms that affect device stability and hence improve device lifetime . The ultimate goal is to achieve photovoltaic devices with power conversion efficiency above 20%, and the encapsulated device can exhibit less than 20% decay in accelerated aging experiments with 1000 hours of continuous illumination.

传统铅基钙钛矿的光学带隙在1.5 eV附近，尽管其效率已达22.7%，但根据shockley-Queisserd理论这并不是最适合做光伏半导体的带隙。近红外光子的吸收损失，使得这类半导体的SQ极限效率只有30%，同时大量的铅也不利于环保。针对这些问题，我们提出以锡铅共掺的方式构造新型钙钛矿半导体，通过调节锡铅比例，获得最佳光学带隙（1.2-1.3eV），其SQ极限效率可达33%。.本项目将深入研究这类锡铅共掺钙钛矿的能级调控规律，结构形貌特性和光物理性质，构筑新型的具有最佳光学带隙的锡铅共掺钙钛矿太阳电池，建立适合这一新型钙钛矿半导体体系的构效关系，深入理解材料特性和器件结构对电荷分离、输运、收集的影响，制备出高性能器件，同时阐明影响稳定性的物理机制，提升器件寿命。最终目标是实现转换效率在20%以上的光伏器件，且封装器件在1000小时连续光照的加速老化实验中，衰减小于20%。

针对现有铅基钙钛矿太阳能电池光谱响应较窄、环境不友好等关键问题，本项目从材料的可控制备出发，深入研究这类锡铅共掺型材料的结构形貌特性和光物理特性，设计并优化器件中的能级匹配、界面接触等，深入理解材料特性和器件结构对电荷分离、输运、收集的影响，制备出高性能的单节太阳能电池器件，并且初步实现窄带隙锡铅共混太阳能电池和铅基太阳能电池的一体化叠层电池。同时理解这类电池退化的物理机制，提升器件的寿命。本项目拟解决的关键科学问题是阐明锡铅共混型钙钛矿太阳能电池材料的“组分结构和凝聚态结构与薄膜的光电特性和器件光伏性能的内在关联。项目完全达到了项目预期目标，实现带隙宽度在1.1-1.3 eV之间的窄带隙锡铅共混型钙钛矿材料的可控制备；系统研究并阐明窄带隙锡铅共混型钙钛矿的基本光物理特性和参数；实现了单节超过20%的效率，超过预期目标。