Two-dimensional lead-free perovskite Cs 3 Bi 2 I 8.3 Br 0.7 single crystals with anisotropic ion migration and hard X-ray responses

• Published in: Journal of materials chemistry. C, Materials for optical and electronic devices Vol. 12; no. 28; pp. 10613 - 10620
• Main Authors: Li, Xiang, Zhang, Guodong, Hua, Yunqiu, Sun, Xue, Liu, Jiaxin, Liu, Hongjie, Yue, Zhongjie, Zhai, Zhongjun, Xia, Haibing, Tao, Xutang
• Format: Journal Article
• Language: English
• Published: 18.07.2024
• ISSN: 2050-7526; 2050-7534
• DOI: 10.1039/D4TC01131G

All-inorganic Bi-based perovskite single crystals have been regarded as one of the semiconductors for X-ray detection due to their high absorption coefficient and excellent carrier transport properties. Herein, the low-dimensional centimeter-sized Cs 3 Bi 2 I 8.3 Br 0.7 , Cs 3 Bi 2 I 8.5 Br 0.5 , and Cs 3 Bi 2 I 9 single crystals were successfully grown using the vertical Bridgeman method. With the ratio of Br/I increased to 0.7/8.3, the crystal structures of these homologues transform from zero-dimensional (0D) Cs 3 Bi 2 I 9 (space group: P 6 3 / mmc ) to two-dimensional (2D) Cs 3 Bi 2 I 8.3 Br 0.7 (space group: P 3̄ m 1). The anisotropic properties of Cs 3 Bi 2 I 8.3 Br 0.7 single crystals with a layered structure were systematically investigated. Despite a high sensitivity (7579 μC Gy air −1 cm −2 ) and a low detection limit (101.85 nGy air s −1 ) under a low electric field of 100 V mm −1 , the (1̄20) plane device shows severe dark current baseline drift under a high electric field of 400 V mm −1 due to the low ion activation energy of 241.24 meV. In compasion, the (001) plane device exhibits a stable and non-drifting dark current baseline and a high sensitivity of 1.46 × 10 4 μC Gy air −1 cm −2 at 25 °C under 400 V mm −1 due to the high ion activation energy of 580.62 meV. As the temperature increases to 75 °C, the sensitivity of the (001) plane was further increased to 1.89 × 10 4 μC Gy air −1 cm −2 . The anisotropic ion migration and X-ray detection performances are attributed to the difference of carrier transportation and ion activation energy along intra-layer and inter-layer directions. Our results show that anisotropic engineering is an efficient way for enhancing the X-ray detection performances of 2D Cs 3 Bi 2 I 8.3 Br 0.7 single crystals.