Temperature-induced localized exciton dynamics in mixed lead–tin based CH3NH3Pb1−xSnxI3 perovskite materials

Of late, tremendous research efforts have been made to obtain Pb-free low-toxicity halide perovskites. In this regard, the Sn-based perovskite is the focus of attention because of its properties being similar to those of Pb. This paper explores the fundamentals of temperature-induced dynamics of localized excitons in mixed Pb–Sn based CH3NH3Pb1−xSnxI3 perovskite materials. A quantitative model using the Monte Carlo simulation of exciton hopping and relaxation is developed to compute the photoluminescence (PL) peak energy, in addition to the PL line-width over a temperature regime of 10 K–300 K. The temperature-induced changes in the bandgap expansion allow the quantitative fit of our calculation to the experimental results. We show that the PL peak energies in CH3NH3PbI3 and CH3NH3Pb1−xSnxI3 are blue shifted due to the fact that the excitons are localized with higher energy localized states with increasing temperatures. It has also been found that the amount of redshift in PL peak energy decreases with an increase in Sn contents while the full width at half maximum increases in increased Sn content perovskite materials. These results give a deep insight into the exciton dynamics in CH3NH3Pb1−xSnxI3, further aimed at efficient applications in optoelectronic devices.