Effects of Crystal Morphology on the Hot-Carrier Dynamics in Mixed-Cation Hybrid Lead Halide Perovskites

Ultrafast pump-probe spectroscopies have proved to be an important tool for the investigation of charge carriers dynamics in perovskite materials providing crucial information on the dynamics of the excited carriers, and fundamental in the development of new devices with tailored photovoltaic properties. Fast transient absorbance spectroscopy on mixed-cation hybrid lead halide perovskite samples was used to investigate how the dimensions and the morphology of the perovskite crystals embedded in the capping (large crystals) and mesoporous (small crystals) layers affect the hot-carrier dynamics in the first hundreds of femtoseconds as a function of the excitation energy. The comparative study between samples with perovskite deposited on substrates with and without the mesoporous layer has shown how the small crystals preserve the temperature of the carriers for a longer period after the excitation than the large crystals. This study showed how the high sensitivity of the time-resolved spectroscopies in discriminating the transient response due to the different morphology of the crystals embedded in the layers of the same sample can be applied in the general characterization of materials to be used in solar cell devices and large area modules, providing further and valuable information for the optimization and enhancement of stability and efficiency in the power conversion of new perovskite-based devices.

Automated summary

Ultrafast pump-probe spectroscopies are crucial for investigating charge carriers dynamics in perovskite materials, providing valuable information on excited carriers' dynamics and aiding in the development of new devices with tailored photovoltaic properties. Studies on mixed-cation hybrid lead halide perovskite samples showed that small crystals embedded in the mesoporous layer can retain carrier temperature for a longer period compared to large crystals, highlighting the importance of crystal dimensions and morphology in hot-carrier dynamics. The high sensitivity of time-resolved spectroscopies in discerning the transient response due to variations in crystal morphology within the same sample can be applied to optimize stability and efficiency in perovskite-based devices for solar cell applications.