MA-activated lattice shrinkage and bandgap renormalization advancing the stability of FA1-xMAxPbI3 (x=0–1) perovskites photovoltaic

Generally, referring to the stability of perovskite, the most studied perovskite material has been MA-free mixed-cation perovskite. The precise role of MA in the light-thermal-humid stability of perovskite solar cells still lacks of a systematically understanding. In this work, the evolution of crystallographic structures, intermediate phase, ultrafast dynamics, and thermal decomposition behavior of MA-mixed perovskite FA1-xMAxPbI3 (x=0–100%) are investigated. The influence of MA on the stability of devices under heat, light, and humidity exposure are revealed. In the investigated compositional space (x=0–100%), device efficiencies vary from 19.5% to 22.8%, and the light, thermal, and humidity exposure stability of the related devices are obviously improved for FA1-xMAxPbI3 (x=20%–30%). Incorporation 20%–30% of MA cations lowers nucleation barrier and causes a significant volume shrinkage, which enhances the interaction between FA and I, thus improving crystallization and stability of the FA1-xMAxPbI3. Thermal behavior analysis reveals that the decomposition temperature of FA0.8MA0.2PbI3 reaches 247 ​°C (FAPbI3, 233 ​°C) and trace amounts of MA cations enhance the thermal stability of the perovskite. Remarkably, we observe lattice shrinkage using spherical aberration corrected transmission electron microscope (AC-TEM). This work implies that stabilizing perovskites will be realized by incorporating trace amounts of MA, which improve the crystallization and carrier transport, leading to improved stability and performances. The evolution of crystallographic structures, intermediate phase, ultrafast dynamics and thermal decomposition behavior of MA-mixed perovskite (FA1-xMAxPbI3, x ​= ​0%–100%) were systematically investigated. MA incorporation improves the stability of the perovskite by enhancing interactions between FA and I through shrinkage of the cubo-octahedral volume. This work has important implications for the control of A-site cations and the design of more stable perovskite structures on a microscopic scale. [Display omitted] •Trace of MA+ in FA1-xMAxPbI3 lowers nucleation barriers and improves thermal stability of FA1-xMAxPbI3 compared to FAPbI3.•The lattice shrinkage caused by MA ​+ ​substitution is the origins of enhanced light-thermal humid stability of device.•MA ​+ ​induces obvious bandgap renormalization in FA1-xMAxPbI3, increasing electron effective mass.