Thermochromic Cs2 AgBiBr6 Single Crystal with Decreased Band Gap through Order-Disorder Transition

Yaru Zhang; Yilong Song; Yuan Lu; Zhuang Zhang; Yang Wang; Yang Yang; Qingfeng Dong; Yi Yu; Peng Qin; Fuqiang Huang

doi:10.1002/smll.202201943

Thermochromic Cs₂ AgBiBr₆ Single Crystal with Decreased Band Gap through Order-Disorder Transition

Small. 2022 Jun;18(24):e2201943. doi: 10.1002/smll.202201943. Epub 2022 May 16.

Authors

Yaru Zhang^{1

2}, Yilong Song³, Yuan Lu⁴, Zhuang Zhang^{1

2}, Yang Wang^{1

2}, Yang Yang³, Qingfeng Dong³, Yi Yu⁴, Peng Qin^{1

2}, Fuqiang Huang^{1

2

5}

Affiliations

¹ State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai, 200050, China.
² Center of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Science, Beijing, 100049, China.
³ State Key Laboratory of Supramolecular Structure and Materials, College of Chemistry, Jilin University, Changchun, 130012, China.
⁴ School of Physical Science and Technology, ShanghaiTech University, Shanghai, 201210, China.
⁵ State Key Laboratory of Rare Earth Materials Chemistry and Applications, College of Chemistry and Molecular Engineering, Peking University, Beijing, 100871, China.

PMID: 35570752
DOI: 10.1002/smll.202201943

Abstract

Lead-free Cs₂ AgBiBr₆ double perovskite is considered to be a promising alternative to the traditional lead-based analogues due to its long carrier lifetime, high structural stability, and non-toxicity. However, the large band gap limits its absorption of visible light, which is not conducive to further optoelectronic applications. Herein, a thermochromic strategy is reported to decrease the band gap of Cs₂ AgBiBr₆ by approximately 0.36 eV, obtaining the smallest reported band gap of 1.69 eV under ambient conditions. The experimental data indicate that after annealing the Cs₂ AgBiBr₆ single crystals at 400 °C, the silver (Ag) and bismuth (Bi) atoms occupy the B-site in a random way and form a partially disordered configuration. The formation of the antisite defects broadens the band edges and decreases the band gap. This work offers new insights into the preparation of narrow band gap lead-free double perovskites, and a deep understanding of their structural and electronic properties for further development in photoelectric devices.

Keywords: lead-free perovskites; narrow band gap; order-disorder transition; thermochromic strategy.

Abstract

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