Fabrication of Thin Films from Powdered Cesium Lead Bromide (CsPbBr3) Perovskite Quantum Dots for Coherent Green Light Emission

摘要

High-quality thin films were obtained directly by spin-coating glass substrates with suspensions of powdered cesium lead bromide (CsPbBr_(3)) perovskite quantum dots (PQDs). The structural properties of the films were characterized via transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD) analysis, and atomic force microscopy (AFM). The crystal structure of the CsPbBr_(3) PQDs was unique. The optical behavior of the CsPbBr_(3) PQDs, including absorption and emission, was then investigated to determine the absorption coefficient and band gap of the material. The CsPbBr_(3) PQDs were evaluated as active lasing media and irradiated with a pulsed laser under ambient conditions. The PQDs were laser-active when subjected to optical pumping for pulse durations of 70–80 ps at 15 Hz. Amplified spontaneous emission (ASE) by the CsPbBr_(3) PQD thin films was observed, and a narrow ASE band (～5 nm) was generated at a low threshold energy of 22.25 μJ cm~(–2). The estimated ASE threshold carrier density (n _(th)) was ～7.06 × 10~(18) cm~(–3). Band-gap renormalization (BGR) was indicated by an ASE red shift and a BGR constant of ～27.10 × 10~(–8) eV. A large optical absorption coefficient, photoluminescence (PL), and a substantial optical gain indicated that the CsPbBr_(3) PQD thin films could be embedded in a wide variety of cavity resonators to fabricate unique on-chip coherent light sources.