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.
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