Guo Yanru, Yuan Shuai, Zhu Dongping, Yu Man, Wang Hao-Yi, Lin Jun, Wang Yi, Qin Yujun, Zhang Jian-Ping, Ai Xi-Cheng
Department of Chemistry, Renmin University of China, Beijing 100872, China.
School of Materials Engineering, Xi'an Aeronautical University, Xi'an 710077, China.
Phys Chem Chem Phys. 2021 Mar 18;23(10):6162-6170. doi: 10.1039/d0cp06575g.
Grain boundary trap passivation in perovskite films has become one of the most effective strategies for suppressing the charge recombination and enhancing the photovoltaic performance of perovskite solar cells, whereas the relevant trap-state properties and the charge carrier dynamics need to be further clarified. In this work, the CH3NH3Cl (MACl) additive is introduced into the MAI:PbI2 precursor solution to obtain perovskite films comprising various grain sizes with distinct grain boundaries and trap-state properties. The influence of grain boundary traps passivated with the MACl additive on trap-state properties and charge carrier transport/recombination dynamics is systematically studied with time-resolved spectroscopic and transient photoelectric characterization. Specifically, the MACl amount determines the content of the PbI2 residual in the final perovskite, leading to photoluminescence quenching induced by charge transfer. The trap-state distribution result reveals that the deep-level traps at the grain boundaries as the main sources of charge recombination centers are dramatically passivated. Low-temperature photoluminescence spectroscopy distinguishes and compares the trap-state emission related to different perovskite phases. Transient photoelectric measurements including photovoltage decay and charge extraction further demonstrate that the boundary trap passivation can effectively promote charge transport and inhibit charge recombination in devices treated with the optimized MACl amount. As a result, the corresponding device possesses superior photovoltaic parameters to the control device. This work proposes a systematic understanding of the grain boundary trap passivation strategy and provides a new insight into the development of high-performance perovskite solar cells.
钙钛矿薄膜中的晶界陷阱钝化已成为抑制电荷复合和提高钙钛矿太阳能电池光伏性能的最有效策略之一，然而相关的陷阱态性质和电荷载流子动力学仍需进一步阐明。在这项工作中，将CH3NH3Cl（MACl）添加剂引入到MAI:PbI2前驱体溶液中，以获得具有不同晶界和陷阱态性质的各种晶粒尺寸的钙钛矿薄膜。利用时间分辨光谱和瞬态光电表征系统地研究了用MACl添加剂钝化的晶界陷阱对陷阱态性质和电荷载流子传输/复合动力学的影响。具体而言，MACl的量决定了最终钙钛矿中PbI2残余物的含量，导致电荷转移引起的光致发光猝灭。陷阱态分布结果表明，作为电荷复合中心主要来源的晶界处的深能级陷阱被显著钝化。低温光致发光光谱区分并比较了与不同钙钛矿相相关的陷阱态发射。包括光电压衰减和电荷提取在内的瞬态光电测量进一步表明，边界陷阱钝化可以有效地促进电荷传输并抑制用优化的MACl量处理的器件中的电荷复合。结果，相应的器件具有优于对照器件的光伏参数。这项工作提出了对晶界陷阱钝化策略的系统理解，并为高性能钙钛矿太阳能电池的开发提供了新的见解。
