Excitonic gain and laser emission from mixed-cation halide perovskite thin films

Abstract

Organic–inorganic halide perovskites have recently developed into a potential semiconductor coherent light emitter candidate beyond their promise in solar cell applications. However, despite the ample demonstrations of perovskite lasers, experimental results on the origin of optical gain in perovskites are still elusive. Here, we analyze the excitonic gain in the green from mixed-cation halide perovskites Cs0.17[CH(NH2)2]0.83PbBr3 (Cs0.17FA0.83PbBr3) by both low temperature absorption/emission spectroscopies and ultrafast pump–probe transient absorption experiments. The perovskite thin films show a robust excitonic feature up to room temperature, with estimated exciton binding energy E b =43.8 meV, which can be maintained under high electronic excitations that are required for lasers. By using a high-quality (Q=1350) vertical cavity consisting of sputtered dielectric HfO2/SiO2 distributed Bragg reflectors with perovskite optical gain medium embedded inside, we have demonstrated excitonic-gain-enabled optically pumped lasing, with improved threshold of 13.5±1.4 μJ/cm2 and device longevity lifetime >35 h (108 laser shots) at ambient environment under sustained pulsed optical excitations (3.493 eV, τpulse=0.34 ns, 1 kHz). Understanding and exploiting excitonic gain from perovskite thin film materials may help to further boost the performance of perovskite-based lasers.