All-inorganic lead-free luminescent metal halides doped with ns2-metal ions have displayed great promise in next-generation solid-state lighting owing to their superior optical properties and easy solution processibility.
However, the photoluminescence (PL) origin of ns2-metal ion-doped metal halides is unknown, and many recent studies have attributed it to the misinterpreted self-trapped exciton (STE) emission. Furthermore, due to a lack of suitable luminescent centers that allow for efficient energy transfer (ET) with minimal energy loss, achieving efficient and tunable white-light emission in metal halides remains difficult.
The research group led by Professor Xueyuan Chen from the Chinese Academy of Sciences’ Fujian Institute of Research on the Structure of Matter developed a new class of extremely effective and dual-band-tunable white-light emitters based on Bi3+/Te4+co-doped perovskite derivative Cs2SnCl6 microcrystals (MCs). The research was in Angewandte Chemie International Edition.
The Bi3+ and Te4+ ions in singly-doped MCs exhibited intense blue and yellow PL originating from the inter-configurational 3P0,1→1S0 transitions at 456 and 565 nm with large Stokes shifts, broad emission bands, and high PL quantum yields (QYs) of 60.6% and 84.6%, respectively, due to strong electron-phonon coupling in the spatially confined 0D structure of Cs2SnCl6.
Due to the strong temperature dependence of the spin-forbidden 3P0→1S0 and spin-orbital allowed 3P1→1S0 transitions of Bi3+, the authors discovered a spectacular transition in the PL lifetime from 1.20 ms at 10 K to 1.49 μs at 300 K in Cs2SnCl6: 1.1% Bi3+, as solid evidence for the isolated Bi3+ emission.
Furthermore, they achieved dual-band-tunable white-light emissions in Cs2SnCl6: Bi3+/Te4+MCs with excellent structure-, air-, photo- and anti-water stability and a PLQY of up to 68.3% through efficient ET from Bi3+ to Te4+.
This research adds to the understanding of Bi3+ and Te4+ excited-state dynamics in Cs2SnCl6, as well as a general approach to achieving single-composition white-light emitters based on lead-free metal halides using ns2-metal ion co-doping.
Zhang, W., et al. (2022) Dual-Band-Tunable White-Light Emission from Bi3+/Te4+ Emitters in Perovskite-Derivative Cs2SnCl6 Microcrystals. Angewandte Chemie International Edition. doi.org/10.1002/anie.202116085.