Influence of the MACl additive on grain boundaries, trap-state properties, and charge dynamics in perovskite solar cells

• Published in: Physical chemistry chemical physics : PCCP Vol. 23; no. 1; pp. 6162 - 617
• Main Authors: Guo, Yanru, Yuan, Shuai, Zhu, Dongping, Yu, Man, Wang, Hao-Yi, Lin, Jun, Wang, Yi, Qin, Yujun, Zhang, Jian-Ping, Ai, Xi-Cheng
• Format: Journal Article
• Language: English
• Published: England Royal Society of Chemistry 18.03.2021
• Subjects: Carrier recombination; Carrier transport; Charge transport; Control equipment; Current carriers; Grain boundaries; Grain size; Low temperature; Passivity; Perovskites; Photoelectricity; Photoluminescence; Photovoltaic cells; Properties (attributes); Solar cells
• ISSN: 1463-9076; 1463-9084
• 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 CH 3 NH 3 Cl (MACl) additive is introduced into the MAI:PbI 2 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 PbI 2 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. A large-grained perovskite induced by MACl with effectively passivated deep-level traps at grain boundaries is systematically studied via transient dynamics measurements.