Efficient Optical Amplification in the Nanosecond Regime from Formamidinium Lead Iodide Nanocrystals

Abstract

Lead halide perovskite nanocrystals (NCs) were recently found to exhibit extraordinary optical amplification properties. The great majority of such studies implemented ultrashort photon pulses in the femtosecond regime to initiate the stimulated emission process. Yet the realization of practical lasing applications based on such materials is crucially dependent on their ability to sustain optical amplification at significantly longer time scales, at which major losses associated with spontaneous emission and nonradiative recombination occur. Herein we demonstrate highly efficient amplified spontaneous emission (ASE) from close-packed films of formamidinium lead iodide perovskite (FAPbI3) NCs under excitation in the nanosecond regime. Systematic optimization of the NC processing and thermal treatment yields solids that exhibit high ASE net modal gain up to 604 cm–1 and weakly temperature sensitive ASE thresholds with room-temperature values as low as 140 μJ cm–2. The efficient optical amplification using excitation pulses comparable to the exciton lifetime combined with the excellent chemical durability and air stability of FAPbI3 NCs renders them outstanding gain media for continuous-wave lasers in the red and near-infrared.