Low temperature photoluminescence properties of CsPbBr₃ quantum dots embedded in glasses

The photoluminescence properties of perovskite CsPbBr₃ QDs embedded in glasses were investigated at cryogenic temperature in the range of 40-240 K. CsPbBr₃ QDs with radii of 3.3 nm, 4.2 nm and 4.8 nm were precipitated in phosphate glasses using conventional thermal treatment. Photoluminescence (PL) integral intensities, bandgap energies and full with at half maximum of the PL bands of CsPbBr₃ QDs showed a strong dependence on temperature. An exciton binding energy of ∼40 meV was derived from the temperature-dependent emission intensity. Optical phonon energy involved in the exciton-phonon interaction was found to be ∼56 meV, about three times as that of the single phonon energy. Exciton-phonon coupling strength and the lattice thermal expansion coefficient were strongly dependent on the size of CsPbBr₃ QDs, and as a result, inflection temperature of the PL peak energies of CsPbBr₃ QDs increased as the size increased.