Low-Temperature Photoluminescence Studies of CsPbBr3 Quantum Dots

Cesium lead halide pervoskite semiconductors are being extensively studied due to unprecedentedly high luminescence efficiency and concomitant narrow emission line width. Here, we report photophysical properties of CsPbBr3 quantum dots having different sizes. Notably 5.5 nm sized CsPbBr3 quantum dots reveal 95% photoluminescence (PL) quantum yield at room temperature. Moreover, signature of the stimulated emission is observed at low temperature for excitation fluence as low as ∼4.16 μW (Xe lamp excitation). Even though CsPbBr3 quantum dots reveal the red shift in band gap at low temperature, similar to the single crystal, the exciton–phonon interaction is profoundly affected by the quantum size effects. Temperature-dependent optical studies reveal an anomalous decrease in exciton-LO phonon coupling in small-sized quantum dots aside from expected higher exciton binding energy. Observed stimulated emission in low-sized CsPbBr3 quantum dots has implications in realizing a quantum dot based laser.