Compositional engineering of ZnBr-doped CsPbBr perovskite nanocrystals: insights into structure transformation, optical performance, and charge-carrier dynamics

Compositional engineering of CsPbBr 3 perovskite nanocrystals (PNCs) via Zn( ii )-doping is an effective way to passivate the defect states, improve the stability, and photoluminescence (PL) efficiency of PNCs for optoelectronic applications. The increase in doping of ZnBr 2 results in a gradual transformation of CsPbBr 3 into Cs 4 PbBr 6 through the formation of intermediate CsPbBr 3 -Cs 4 PbBr 6 heterostructures. The structural transformation is due to the replacement of Pb 2+ ions at the B-site with Zn 2+ ions supplied by ZnBr 2 . Furthermore, the presence of additional Br − ions not only facilitates the transition process but also inhibits surface defects in PNCs, leading to an impressive PL quantum yield of 98.6%. The mechanism behind this transformation and the enhancement of optical properties was investigated through experimental characterization techniques. Time-resolved PL and transient absorption spectroscopy revealed the suppression of nonradiative carrier trapping centers and the generation of shallow energy states, facilitating radiative recombination with the addition of ZnBr 2 . Furthermore, temperature-dependent PL and TRPL studies revealed that radiative recombination and de-trapping were facilitated by temperature changes. At elevated temperatures, ZnBr 2 -doped PNCs exhibited better color stability than CsPbBr 3 , making them suitable for application in light-emitting devices. Finally, we developed a white light emitting diode (WLED) using a blue LED, Zn-doped CsPbBr 3 PNCs, and K 2 SiF 6 :Mn 4+ , which resulted in the emission of white light with impressive features: a high luminous efficiency of 58 lm W −1 , a color rendering index of 80.6, and generated color coordinates of (0.3312, 0.3253) with a correlated temperature of 5584 K, Furthermore, the WLED achieved a wide color gamut, exhibiting 129.74% of the NTSC and 96.88% of the BT-2020. ZnBr 2 incorporated CsPbBr 3 transformed into to Cs 4 PbBr 6 via the intermediate CsPbBr 3 /Cs 4 PbBr 6 heterostructure, resulting in improved PL characteristics (near unity PLQY).