Terahertz Conductivity within Colloidal CsPbBr3 Perovskite Nanocrystals: Remarkably High Carrier Mobilities and Large Diffusion Lengths

Abstract

Colloidal CsPbBr₃ perovskite nanocrystals (NCs) have emerged as an excellent light emitting material in last one year. Using time domain and time-resolved THz spectroscopy and density functional theory based calculations, we establish three fold free carrier recombination mechanism, namely, non-radiative Auger, bi-molecular electron-hole recombination and inefficient trap-assisted recombination in 11 nm sized colloidal CsPbBr₃ NCs. Our results confirm a negligible influence of surface defects in trapping charge carriers, which, in turn, results in to desirable intrinsic transport properties, from the perspective of device applications, such as remarkably high carrier mobility (~4500 cm²V^-1s^-1), large diffusion length (> 9.2 μm) and high luminescence quantum yield (80%). In spite of being solution processed, and possessing a large surface to volume ratio, this combination of high carrier mobility and diffusion length, along with nearly ideal photoluminescence quantum yield, is unique compared to any other colloidal quantum dot system.