钛基无铅钙钛矿Cs2TiI6光伏薄膜与器件研究

Perovskite solar cells have developed very fast in recent years. However, the development of traditional perovskite materials is limited by the poor stability due to the organic components and by the toxicity due to the element lead. This project focuses on the novel all-inorganic titanium-based perovskite halide materials. This new material exhibits great potentials. Compared with the traditional methyl ammonium lead iodide, Ti-based perovskite material shows similar optoelectronic properties but much higher environmental stability. In this project, we will investigate Cs2TiI6, which has proper optical bandgap for photovoltaic application. We will control the preparation of Cs2TiI6 thin films and study the basic properties of the films. The charge carrier mobility, absorption coefficient, band structure and work function of the thin films will be investigated. The influence of grain boundaries on the film electronic properties will be in-situ investigated. By designing proper device structure, optimizing Cs2TiI6 morphology and geometry, choosing proper carrier extraction layers and interfacial modification, the photogenerated charge carriers will be effectively extracted to the external circuit. Our aim is to fabricate stable (under 85 °C + 85 RH% for 2000 h, the efficiency of our solar cells will keep above 90% of the initial values) and high-performance (power conversion efficiency above 10%) solar cells. The accomplishment of this project will contribute to the non-toxic, environmentally stable and efficient perovskite photovoltaics.

钙钛矿太阳能电池近年来发展迅猛。然而，传统钙钛矿材料由于有机成分引发的不稳定性和重金属铅导致的毒性，严重制约了其实际应用。本项目针对新型全无机钛基无铅钙钛矿材料进行研究。该新材料表现出巨大潜力：与甲铵碘化铅相比，其主要光电性质相近，但稳定性大大增强。项目瞄准带隙适当的Cs2TiI6材料，实现其薄膜的可控制备；对薄膜基本性质进行表征，并分析其载流子迁移率、吸收系数、能带结构、功函数等重要信息；从微观和宏观两个角度上原位探索晶界对薄膜电学性质的影响；设计合理的器件结构，通过优化Cs2TiI6形貌和几何参数，以及载流子传输层材料选择和界面调控，从而改善光生电荷的有效传输和收集；最终实现稳定（85°C+85RH%环境2000h，器件效率保持在初始值90%以上）、高效（能量转换效率>10%）的Cs2TiI6太阳能电池的制备。项目的完成将对实现无毒、环境稳定、高效的钙钛矿光伏器件做出贡献。

本项目围绕钛基卤化物双钙钛矿纳米晶的可控制备，光物理性质及其器件应用展开了系统的研究工作。针对八面体中心Ti4+离子的强极化能力，设计具有不同抗极化能力的I-/Br-离子组分调控方式，通过阶序控温-冰浴冷却的方法改进了传统的热注入技术，制备出了系列Cs2TiBrxI6-x双钙钛矿纳米晶材料；通过对系列材料的稳定性进行评价，发现提高Br的比例可改善材料的稳定性；选取Cs2TiBr6为代表，对其光物理性质进行.了系统的研究，其超快光谱及飞秒Z扫描结果表明其单分子复合速率随着温度的下降而降低，但是双分子复合速率的规律则相反，非线性吸收截面高达1i070GM；鉴于该材料优异的光电性质在光电器件中具有巨大潜力，我们进一步通过晶界调控的方式，减弱晶界处的载流子-声子散射，促进了载流子迁移，进而优化了卤化物双钙钛矿太阳能电池的的稳定性和器件性能；在此基础上，通过氧化物电子传输层和表面修饰两种方式，提高填充因子，进而达到高并联电阻，优化了载流子传输模式，改善了开路电压、短路电流密度等关键指标。此外，我们还构建了忆阻器件，可实现人工神经突触信号模拟。本项目已发表高水平学术论文7篇，尚有部分工作仍在整理中。本项目的实施不但对于钛基双钙钛矿卤化物纳米晶材料的制备和应用做出了系统的基础性工作，还对其在光电、智能忆阻材料等应用研究提供了坚实的科学基础和技术储备。