Shixun Wang,Ran Shi,Bing Tang,Yuan Xiong,Arsenii Portniagin,Xin Zhao,Stephen V. Kershaw,Run Long,Andrey L. Rogach
The co-doping of double perovskites is a useful approach in terms of improving their stability and photoluminescence quantum yield. Herein, Bi3+ and Te4+ cations have been co-doped into Cs2AgInCl6 nanocrystals. Doping with Te4+ cations promotes radiative recombination of self-trapped excitons due to increased defect formation energies of silver and indium vacancies, according to experimental and theoretical results. When used in excess, the TeO2 precursor would generate residual TeO2, Te2O3Cl2, R2TeO, or all three of them, which confined undesired chlorine ions on oxygen vacancies to counteract the pull from the Cs2AgInCl6 host, resulting in improved coordination with surface oleic acid ligands. As a result, 1% Bi and 8% Te co-doped Cs2AgInCl6 nanocrystals reach a high photoluminescence quantum yield of 34% and show an improved stability, maintaining over 70% of their original emission intensity after storage for more than 1 month. These findings are important in the context of producing high-performance properly doped double perovskite nanocrystals for optoelectronic applications.
Recently, Bi-doped Cs 2 Ag 0.6 Na 0.4 InCl 6 lead-free double perovskites demonstrating efficient warm-white emission have been reported. To enable the solution processing and enrich the application fields of this promising material, here a colloidal synthesis of Cs 2 Ag 1− x Na x In 1− y Bi y Cl 6 nanocrystals is further developed. Different from its bulk states, the emission color temperatures of the nanocrystal can be tuned from 9759.7 to 4429.2 K by Na + and Bi 3+ incorporation. Furthermore, the newly developed nanocrystals can break the wavefunction symmetry of the self-trapped excitons by partial replacement of Ag + ions with Na + ions and consequently allow radiative recombination. Assisted with Bi 3+ ions doping and ligand passivation, the photoluminescence quantum yield of the Cs 2 Ag 0.17 Na 0.83 In 0.88 Bi 0.12 Cl 6 nanocrystals is further promoted to 64%, which is the highest value for lead-free perovskite nanocrystals at present. The new colloidal nanocrystals with tunable color temperature and efficient photoluminescence are expected to greatly advance the research progress of lead-free perovskites in single-emitter-based white emitting materials and devices.
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