Hybrid perovskites have recently emerged as promising material for photovoltaics due to their excellent optoelectronic properties and low-cost solution processability. Despite the impressive power conversion efficiencies (PCE) achieved so far (23.3%), major issues still need to be resolved prior to commercialization. One of the main issue represent the big gap between reported PCE and theoretical Shockley-Queisser (SQ) limit (~31%). In order to increase PCE of these devices close to SQ limit, a better understanding of charge recombination mechanisms is necessary. In this regard, this thesis presents a new type of excitation-dependent microscopy which enables to reveals local charge recombination mechanism of thin film and solar cell device.
Another important issue is halide phase separation in mixed halide perovskite under illumination. Halide phase separation prevent these materials to be incorporated into devices. Therefore, suppressing halide phase separation represent an important issue for the community. Third chapter of this thesis present spectroscopic observation of halide phase separation. Based on these observations a physical model is built which rationalize all microscopic processes that occur during phase separation. Moreover, our model reveals that mixed halide perovskites can be stabilized against phase separation by tuning the physical properties of perovskite film.