Boosting triplet self-trapped exciton emission in Te(IV)-doped Cs 2 SnCl 6 perovskite variants
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Boosting triplet self-trapped exciton emission in Te(IV)-doped Cs2SnCl6 perovskite variants Ruosheng Zeng1,2, Kun Bai2, Qilin Wei1, Tong Chang1, Jun Yan1, Bao Ke1, Jialuo Huang1, Liushun Wang3, Weichang Zhou3 (), Sheng Cao1, Jialong Zhao1 (), and Bingsuo Zou1 () 1
School of Physical Science and Technology, MOE Key Laboratory of New Processing Technology for Non-ferrous Metals and Materials, Guangxi Key Laboratory of Processing for Non-ferrous Metals and Featured Materials, Guangxi University, Nanning 530004, China 2 School of Materials Science and Engineering, Guilin University of Electronic Technology, Guilin 541004, China 3 School of Physics and Electronics, Key Laboratory of Low-dimensional Quantum Structures and Quantum Control of Ministry of Education, Key Laboratory for Matter Microstructure and Function of Hunan Province, Synergetic Innovation Center for Quantum Effects and Application, Hunan Normal University, Changsha 410081, China © Tsinghua University Press and Springer-Verlag GmbH Germany, part of Springer Nature 2020 Received: 16 September 2020 / Revised: 23 October 2020 / Accepted: 27 October 2020
ABSTRACT Perovskite variants have attracted wide interest because of the lead-free nature and strong self-trapped exciton (STE) emission. Divalent Sn(II) in CsSnX3 perovskites is easily oxidized to tetravalent Sn(IV), and the resulted Cs2SnCl6 vacancy-ordered perovskite variant exhibits poor photoluminescence property although it has a direct band gap. Controllable doping is an effective strategy to regulate the optical properties of Cs2SnX6. Herein, combining the first principles calculation and spectral analysis, we attempted to understand the luminescence mechanism of Te4+-doped Cs2SnCl6 lead-free perovskite variants. The chemical potential and defect formation energy are calculated to confirm theoretically the feasible substitutability of tetravalent Te4+ ions in Cs2SnCl6 lattices for the Sn-site. Through analysis of the absorption, emission/excitation, and time-resolved photoluminescence (PL) spectroscopy, the intense green-yellow emission in Te4+:Cs2SnCl6 was considered to originate from the triplet Te(IV) ion 3P1→1S0 STE recombination. Temperature-dependent PL spectra demonstrated the strong electron-phonon coupling that inducing an evident lattice distortion to produce STEs. We further calculated the electronic band structure and molecular orbital levels to reveal the underlying photophysical process. These results will shed light on the doping modulated luminescence properties in stable lead-free Cs2MX6 vacancy-ordered perovskite variants and be helpful to understand the optical properties and physical processes of doped perovskite variants.
KEYWORDS Cs2SnCl6 perovskite variants, equivalent ion doping, self-trapped exciton (STE) emission, electron-phonon coupling, first principles calculation
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Introduction
Due to the balanced electron and hole mobility, long length of carrier diffusion, high photoluminescence quantum yield (PLQY), strong spin-orbit coupling and low-cost solution preparatio
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