Abstract :

Perovskite nanocrystals show high photoluminescence quantum yield1 as well as efficient performances in optoelectronics devices.2 Unlike traditional colloidal quantum dots, CsPbBr3 nanocrystals exhibit anomalous photoluminescence decay as a function of temperature.3 Our temperature-dependent time-resolved photoluminescence (TRPL) spectroscopy study reveals the presence of localized emission states (~75±15 meV) at longer time delays with reduction of temperature. This delayed emission hasn’t been observed at room temperature PL. The localized emission peak shows anomalous broadening with respect to temperature. The Arrhenius Plot of temperature dependent PL indicates the existence of two activation energies (~77±18 meV and ~12±3 meV) for the non-radiative centers. A qualitative model has been developed which has explained the contrasting behavior of PL decay in CsPbBr3 nanocrystal films. We also demonstrate the low threshold amplified spontaneous emission in these films to hallmark the quality of NCs.