All-inorganic lead-free luminescent metal halides doped with ns2-metal ions have shown great promise in next-generation solid-state lighting because of their superior optical properties and easy solution processibility.
However, the photoluminescence (PL) origin of ns2-metal iondoped metal halides is not well understood and has been ascribed to the misconceived self-trapped exciton (STE) emission in many recent studies. Moreover, it remains challenging to achieve efficient and tunable white-light emission in metal halides due to the lack of suitable luminescent centers that allow for efficient energy transfer (ET) with minimal energy loss.
In a study published in Angewandte Chemie International Edition, the research group led by Prof. CHEN Xueyuan from Fujian Institute of Research on the Structure of Matter of the Chinese Academy of Sciences developed a new class of highly efficient and dual-band-tunable white-light emitters based on Bi3+/Te4+co-doped perovskite derivative Cs2SnCl6 microcrystals (MCs).
Owing to the strong electron–phonon coupling in the spatially confined 0D structure of Cs2SnCl6, the Bi3+ and Te4+ ions in the singly-doped MCs exhibited intense blue and yellow PL originating from the inter-configurational 3P0,1→1S0 transitions at 456 and 565 nm with broad emission bands, large Stokes shifts, and high PL quantum yields (QYs) of 60.6% and 84.6%, respectively.
Specifically, the researchers observed a remarkable transition in the PL lifetime from 1.20 ms at 10 K to 1.49 μs at 300 K in Cs2SnCl6: 1.1% Bi3+, due to the strong temperature dependence of the spin-forbidden 3P0→1S0 and spin-orbital allowed 3P1→1S0 transitions of Bi3+, as solid evidence for the isolated Bi3+ emission.
Besides, through efficient ET from Bi3+ to Te4+, they realized dual-band-tunable white-light emissions in Cs2SnCl6: Bi3+/Te4+ MCs with excellent air-, structure-, photo-, and anti-water stability and a PLQY of up to 68.3%.
This study provides new insights into both excited-state dynamics of Bi3+ and Te4+ in Cs2SnCl6 and a general approach to achieve single-composition white-light emitters based on lead-free metal halides through ns2-metal ion co-doping.
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