Vapor-Assisted Solution Approach for High-Quality Perovskite CH3NH3PbBr3 Thin Films for High-Performance Green Light-Emitting Diode Applications.

The vapor-assisted solution method was developed to prepare high-quality organic-inorganic halide perovskite CH3NH3PbBr3 (MAPbBr3) thin films. We detailedly investigated the effect of evaporation time and temperature of MABr powder on the microstructure, crystallinity, and optical characterizations of MAPbBr3 thin films, and a controllable morphology evolution with varying surface coverage was observed. Temperature-dependent and time-resolved photoluminescence measurements were carried out to investigate the optical transition mechanisms and carrier recombination dynamics of MAPbBr3 thin films. Our results revealed that no structural phase transition occurred within the heating process (10-300 K). In addition to the exciton-related emission, a trapped charge-carrier emission appeared at a critical temperature of 140 K. The corresponding temperature sensitivity coefficient of band gap, exciton binding energy, and optical phonon energy of the MAPbBr3 thin films were extracted from the experimental data. Furthermore, planar perovskite light-emitting diodes (PeLEDs) based on a Al/LiF/TPBi/MAPbBr3/NiO/ITO structure were fabricated, and a high-purity green emission at ∼532 nm with a low line width (25 nm) was achieved. The devices demonstrated remarkable performances with high luminance (6530 cd/m2), current efficiency (8.16 cd/A), external quantum efficiency (4.36%), and power efficiency (4.49 lm/W). This research will provide valuable information for the preparation of high-quality perovskite thin films, facilitating their future applications in novel high-performance PeLEDs.