高效宽带隙钙钛矿太阳电池材料开发与器件优化

Recently, perovskite solar cells have attracted tremendous research interest for application in tandem structured devices. However, the solar to electric power conversion efficiency of perovskites based tandem solar cells are still far below the expected values, which should be primarily ascribed to the presence of severe over-potential energy loss as well as long wavelength photons loss within the large-band-gap perovskite top cells. In this proposal, we aim to develop highly efficient large-band-gap perovskite solar cells by addressing the issues of low open-circuit voltage and low photons transmittance at long wavelengths. The detailed research contents include: (1) investigating the relationship between the composition, band gap and energy levels of the hybrid perovskite materials; (2) rationally designing new electron and hole transport materials with optimized energy levels; (3) optimizing the film deposition and device structure to improve the optical performance for the transporting layers; and (4) exploring the impact of charge transport materials on the performance of large-band-gap perovskite solar cells, improving the photovoltaic performance of large-band-gap perovskite solar cells as well as their potential of tandem applications. The success of this project will pave the way for breaking the single junction silicon solar cells efficiency record and achieving super-high efficiency perovskite-silicon tandem solar cells.

近年来，钙钛矿太阳电池的叠层器件应用研究备受关注，但钙钛矿与硅等窄带隙太阳电池的叠层器件效率还远远低于理想值，其主要原因是宽带隙的钙钛矿电池中存在严重的过电位损耗和长波长光子损失。本项目以开发高性能的宽带隙钙钛矿太阳电池为目标，解决目前宽带隙钙钛矿太阳电池开路电压低、长波长光子透过率不足等问题。具体研究内容为：（1）系统研究钙钛矿的组份-带隙-能级三者间的相互关系，明确宽带隙钙钛矿的能带结构；（2）合理设计并开发新型能级优化的电子和空穴传输材料；（3）优化涂膜工艺和器件结构，从电荷传输材料的光学特性和薄膜厚度等方面优化长波长光子的透过性；（4）探索传输材料对宽带隙钙钛矿太阳电池光伏性能（特别是开路电压性能）的影响和作用机制，提升宽带隙钙钛矿太阳电池光伏性能和叠层应用潜力。该项目的成功实施将为发展高效钙钛矿-硅叠层太阳电池、突破单结硅电池效率记录奠定基础。

宽带隙钙钛矿太阳电池在叠层光伏研究中备受关注，目前钙钛矿与硅等窄带隙太阳电池的叠层器件效率还远远低于理想值，其主要原因是宽带隙的钙钛矿电池中存在严重的过电位损耗和长波长光子损失。本项目围绕宽带系钙钛矿太阳电池的吸光活性层、空穴传输层和电子传输层材料的筛选与设计，开展了系列研究工作。1）探索宽带隙、全无机钙钛矿CsPbI3的薄膜制备方法与相稳定机制；2）调控空穴、电子传输材料HOMO-LUMO能级并探索其与钙钛矿电池Voc相关性；3）发展面向叠层和大面积器件应用的界面电荷传输层制备方法。以带隙为1.75eV的CsPbI3钙钛矿作为研究对象，深入探索了低温（90-100oC）制备与稳定CsPbI3钙钛矿的机制，系统对比了一系列含硫有机小分子作为添加剂对其结晶过程的影响，将宽带隙CsPbI3钙钛矿电池的光电转换效率提升至14%左右，实现全部制备流程在100oC以下完成，有助于其在叠层器件中的应用。发展了以四噻吩乙烯、喹喔啉等为核心单元的新型空穴传输材料，提出了“平面-正交构型杂化”、“共平面π延伸”等分子设计策略，协同调控材料能级、迁移率与成膜性，获得了高性能无需掺杂的有机空穴传输材料，显著提高钙钛矿太阳电池稳定性。在国内首创以锚定自组装过程制备大面积超薄均匀电荷传输层，可最大限度降低传输层厚度以降低光学与电学损失。这一系列工作将有力推进宽带系钙钛矿太阳电池的发展及叠层器件的研发。