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