Pressure-tuned biexciton emission in CH3NH3PbBr3 perovskite quantum dots

Abstract

Pressure-induced evolution of the bandgap, structural phase transitions, and changes in exciton effects can significantly modulate the luminescent properties of lead halide perovskites (LHPs) quantum dots (QDs). Previous studies have indicated that CH3NH3PbBr3 (MAPbBr3) QDs, as a typical low-dimensional LHP material, and their photoluminescence (PL) at ambient conditions are mainly attributed to the radiative recombination of the initially generated excitons upon light absorption and the excitons involving surface states, while the existence of biexciton radiative recombination remains unclear. In this work, we confirm the existence of biexciton radiative recombination in MAPbBr3 QDs at ambient conditions through experimental measurements of excitation-intensity-dependent PL and time-resolved PL (TRPL) spectra at ambient conditions as well as temperature-dependent PL spectra (80–260 K) at ambient pressure. We also establish that the PL of MAPbBr3 QDs primarily originates from the combined effects of three excitons radiative recombination physical processes: biexcitons, initially generated excitons upon light absorption, and excitons involving surface states. Furthermore, through in situ high-pressure PL, absorption, and TRPL spectroscopy measurements, we reveal that the recombination lifetimes and the relative contributions of these three excitons in MAPbBr3 QDs are all subject to alteration in response to the pressure-induced bandgap evolution and the structural phase transitions, thereby modulating their PL emission characteristics.