First-principles time-domain study on enhanced luminescence of nanostructured halide perovskites

Abstract

Metal halide perovskites (MHPs) are receiving tremendous interest as a next-generation light emitting diode (LED) material due to their excellent optical properties. Developing MHPs that satisfy the high luminescence efficiency and economic feasibility is an essential strategy for the practical application as an emission layer in LED. It has been reported that MHP thin-film, which is easy to fabricate over a large area, can achieve bright emissions when the MHPs particles (or grains) are fabricated in a nanocrystal size. The mechanism of the light enhancement is considered to be due to two aspects. First, the increased dominance of the specific surface, which is known to reduce non-radiative recombination channels, delayed the non-radiative process. Second, photogenerated electron-hole carriers mainly undergo non-radiative decay by easily separating and diffusing in bulky size. However, the confinement on carrier diffusion according to size reduction becomes effective, and it is considered because it promotes radiative recombination. However, in addition to the dielectric confinement through the size decrease, nanostructured MHP can have some phenomena such as the reconstruction of the atomic coordination network on the surface, the change in crystalline symmetry, or interaction with additives and electron/hole transport layers in contact. The light enhancement mechanism can be understood by examining the implications of changes in atomic and electronic structural properties occurring in nanostructured MHPs. Based on this understanding, the descriptors that determine the photoelectrochemical properties of MHPs can be identified at the atomic level. This thesis presents the results of investigation of the recombination kinetics of MHPs according to the nanostructuring by performing first-principles non-adiabatic molecular dynamics simulation. The lattice vibration and electronic structure factors that determine luminescence efficiency were identified by analyzing the kinetics of radiative and non-radiative recombination in MHPs. It is expected that the findings can suggest guidelines for developing highly-efficient MHP materials for successful LED applications.