Controlling and Optimizing Amplified Spontaneous Emission in Perovskites

Abstract

Perovskites are currently attracting extensive research interest as a wavelength-tunable lasing material. As a first step towards electrically pumped lasers, numerous investigations have recently reported amplified spontaneous emission (ASE) of optically pumped perovskites with remarkably low thresholds. Here, we investigate the optical aspects of perovskite ASE, in order to establish design principle of materials and devices. We show that compared to solution processed CsPbBr3, vacuum deposition yields superior ASE characteristics with a threshold of 35 μJ/cm2. The optical loss (Rloss) during lateral photon propagation in waveguide mode is identified as a key parameter to determine the ASE quality. With spatially resolved photoluminescence, we determine Rloss as 40 cm-1 and >1000 cm-1 for vacuum and solution processed perovskites, respectively. We present a comprehensive model which relates ASE, gain length, optical loss, temperature, and density of states. Finally, we succeed in demonstrating ASE in the perovskite samples with metal electrodes, mimicking a diode architecture for electrical pumping. Optical spacer layers are shown to play a crucial role to prevent metal absorption loss in waveguide modes.