2, Case Western Reserve University, Cleveland, Ohio, United States
3, Duke University, Durham, North Carolina, United States
4, Duke University, Durham, North Carolina, United States
Hybrid organic-inorganic metal halide perovskites (PVSKs) have attracted interest as next generation solar cell materials due their potential for high power conversion efficiency and simple fabrication methods. Despite the rapid development of PVSKs in the material science field, the characterization of photo-physical properties and dynamics is far from exhaustive, leaving open questions, such as the role of trap states, influence of defects, and the origin of luminescence. PVSK layers show grain-level spatial variations, and conventional spectroscopic analysis tools (such as transient optical absorption spectroscopy) often cannot resolve the heterogeneous grains. Nano imaging tools, such as scanning electron microscopy, can resolve the spatial structure but provide little information on dynamic optical and electronic properties.
Here we demonstrate the use of time-resolved nonlinear optical microscopy, pump-probe microscopy, to measure optical and electron dynamics in PVSKs on the femto- to pico-second timescale and sub-micron spatial scale. We investigate crystalline CH3NH3PbI3 and CH3NH3PbI3-xClx perovskite thin layers deposited on glass substrates and map charge carrier dynamics that result in various nonlinear contrasts: two photon absorption, ground state depletion, and excited state absorption. Based on these contrasts, we can visualize the heterogeneous grains and investigate the influence of different fabrication methods or the presence of electron accepting layers on the electronics properties. In this submission, we will present progress in utilizing pump-probe microscopy for mapping of charge carrier dynamics in order to explore the effects of PVSK composition, manufacturing, and aging.