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

High-quality thin films were obtained directly by spin-coating glass substrates with suspensions of powdered cesium lead bromide (CsPbBr₃) 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 CsPbBr₃ PQDs was unique. The optical behavior of the CsPbBr₃ PQDs, including absorption and emission, was then investigated to determine the absorption coefficient and band gap of the material. The CsPbBr₃ 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 CsPbBr₃ 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 × 10¹⁸ 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 CsPbBr₃ PQD thin films could be embedded in a wide variety of cavity resonators to fabricate unique on-chip coherent light sources.