Efficient and stable emission of warm-white light from lead-free halide double perovskites.
basic_science · Level V
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- Record sourced from PubMed, PMID 30405238.
- Also identified by DOI 10.1038/s41586-018-0691-0.
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Abstract
Lighting accounts for one-fifth of global electricity consumption<sup>1</sup>. Single materials with efficient and stable white-light emission are ideal for lighting applications, but photon emission covering the entire visible spectrum is difficult to achieve using a single material. Metal halide perovskites have outstanding emission properties<sup>2,3</sup>; however, the best-performing materials of this type contain lead and have unsatisfactory stability. Here we report a 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 AgCl<sub>6</sub> octahedron in the excited state. By alloying sodium cations into Cs<sub>2</sub>AgInCl<sub>6</sub>, we break 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<sup>4</sup>. This leads to an increase in photoluminescence efficiency by three orders of magnitude compared to pure Cs<sub>2</sub>AgInCl<sub>6</sub>. The optimally alloyed Cs<sub>2</sub>(Ag<sub>0.60</sub>Na<sub>0.40</sub>)InCl<sub>6</sub> 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. We anticipate that these results will stimulate research on single-emitter-based white-light-emitting phosphors and diodes for next-generation lighting and display technologies.