New lead-free halide double perovskites emitting warm-white light are expected to solve the problems of blue-light hazard and Rare Earth Elements consumption.

Recently materials scientists have developed efficient and stable emission of warm-white light from lead-free halide double perovskites.
The research called “Efficient and stable emission of warm-white light from lead-free halide double perovskites,” which was published in Nature, was led by Professor Jiang Tang, Huazhong University of Science and Technology, and Professor Yanfa Yan, the University of Toledo.

The lead-free double perovskite that exhibits efficient and stable white-light emission via self-trapped excitons that originate from the Jahn–Teller distortion of the AgCl6 octahedron in the excited state. By alloying sodium cations into Cs2AgInCl6, the team breaks the dark transition (the inversion-symmetry-induced parity-forbidden transition) by manipulating the parity of the wavefunction of the self-trapped exciton and reduce the electronic dimensionality of the semiconductor. This leads to an increase in photoluminescence efficiency by three orders of magnitude compared to pure Cs2AgInCl6. The optimally alloyed Cs2(Ag0.60Na0.40)InCl6 with 0.04 per cent bismuth doping emits warm-white light with 86 ± 5 per cent quantum efficiency and works for over 1,000 hours. They anticipate that these results will stimulate research on single emitter-based white-light-emitting phosphors and diodes for next generation lighting and display technologies.

Reference:
Efficient and stable emission of warm-white light from lead-free halide double perovskites.
Jiajun Luo, Xiaoming Wang, Shunran Li, Jing Liu, Yueming Guo, Guangda Niu, Li Yao, Yuhao Fu, Liang Gao, Qingshun Dong, Chunyi Zhao, Meiying Leng, Fusheng Ma, Wenxi Liang, Liduo Wang, Shengye Jin, Junbo Han, Lijun Zhang, Joanne Etheridge, Jianbo Wang, Yanfa Yan, Edward H. Sargent & Jiang Tang.
2018-11-12