Highly stable metal halides Cs 2 ZnX 4 (X = Cl, Br) with Sn 2+as dopants for efficient deep-red photoluminescence

The development of deep-red emitting lead-free metal-halide perovskites with high photoluminescence quantum yields (PLQYs) and outstanding stability remains a major challenge for displays and deep-tissue bioimaging. In this work, we report a facile and convenient solvothermal method to synthesize metal halides Cs 2 ZnX 4 (X = Cl, Br) that however is PL innert at room temperature. Upon composition engineering utilizing Sn 2 + as the dopant, the resulting Cs 2 ZnCl 4 :Sn not only emits strong deep-red PL peaked at 700 nm with the highest 99.4% PLQY among the similar materials so far, but also exhibits excellent structure stability in air (PLQY remains 96% after one year exposure to the atmosphere). Detailed experimental characterizations and theoretical calculations reveal that the deep-red emission stems from self-trapped excitons induced by the Sn 2 + dopant. Particularly, triplet emission ( 3 P 2 -> 1 S 0 ) from Sn-5s 2 orbitals has been observed at low temperature due to the break of parity-forbidden transition. This work provides an important guidance for the development of deep-red light-emitting materials with low price, high efficiency and excellent stability.(c) 2022 Published by Elsevier B.V. on behalf of Chinese Chemical Society and Institute of Materia Medica, Chinese Academy of Medical Sciences.

Automated summary

In this work, deep-red emitting lead-free metal-halide perovskites with high photoluminescence quantum yields (PLQYs) and outstanding stability were synthesized through a solvothermal method. The resulting Cs2ZnCl4:Sn exhibited strong deep-red photoluminescence and excellent structure stability in air, with a PLQY of 99.4% and 96% remaining after one year exposure to the atmosphere, respectively. Detailed experimental characterizations and theoretical calculations revealed that the deep-red emission originated from self-trapped excitons induced by the Sn2+ dopant, and triplet emission from Sn-5s2 orbitals was observed at low temperature.