Temperature-dependent photoluminescent behavior of millimeter-scale Cs4PbBr6 /CsPbBr3 bulk crystals and their application to white light-emitting diodes

The zero-dimensional perovskite composite Cs 4 PbBr 6 /CsPbBr 3 has attracted significant attention for its remarkable photoluminescence (PL), which remains highly effective even in solid state. This work presents a detailed analysis of the steady-state and time-resolved PL (TRPL) behavior of millimeter-scale Cs 4 PbBr 6 /CsPbBr 3 crystals over a temperature range of 80 to 360 K, which covers exciton binding energy, phonon energy, and PL peak energy shifting with increasing temperature. According to the results, Cs 4 PbBr 6 /CsPbBr 3 exhibits high exciton binding energy and phonon energy, with calculated values of 358.7 and 94.8 meV, respectively. Specifically, when the temperature is below similar to 235 K, thermal expansion dominates to influence the TRPL and peak energy, whereas electron-phonon interaction becomes the dominant factor as temperature rises from 235 to 325 K. It is found that Cs 4 PbBr 6 /CsPbBr 3 has a PL behavior similar to CsPbBr 3 , and characterization and TRPL results demonstrate that nanometer-scale CsPbBr 3 crystals embed in the Cs 4 PbBr 6 bulk matrix. Meanwhile, a white light-emitting diode (WLED) device based on Cs 4 PbBr 6 /CsPbBr 3 with luminous efficiency of 64.56 lm/W is fabricated, and its color coordinate is measured as (0.34, 0.31) under 20 mA, which is in close proximity to the standard white color coordinate. Moreover, the color gamut of the device is measured as 128.66 % of the National Television Systems Committee (NTSC). The WLED electroluminescence (EL) spectra show high Correlated Color Temperature (CCT) stability for the working current varying from 5 to 100 mA, and after continuous operation for 12 h, the EL intensity decreases and stabilizes at similar to 70 % of the initial EL intensity. These findings suggest that Cs 4 PbBr 6 /CsPbBr 3 crystals are a promising candidate for WLEDs.(c) 2023 Published by Elsevier Ltd on behalf of The editorial office of Journal of Materials Science &