Reductant Engineering in Stable and High‐Quality Tin Perovskite Single Crystal Growth for Heterojunction X‐Ray Detectors

• Published in: Advanced materials (Weinheim) Vol. 35; no. 48; pp. e2307042 - n/a
• Main Authors: Li, Mingbian, He, Yuhong, Feng, Xiaopeng, Qu, Wei, Wei, Wei, Yang, Bai, Wei, Haotong
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.11.2023
• Subjects: Biocompatibility; Crystal growth; Heterojunction devices; Materials science; Optoelectronics; Oxalic acid; Oxidation; Perovskites; Photovoltaic cells; Reducing agents; Single crystals; Solar cells; stability; Tin; tin perovskites; X‐ray detectors
• ISSN: 0935-9648; 1521-4095
• DOI: 10.1002/adma.202307042

Tin perovskites have emerged as a promising alternative material to address the toxicity of lead perovskites and the low bandgap of around 1.1 eV is also compatible with tandem solar cell applications. Nevertheless, the optoelectronic performance of solution‐processed tin perovskite single‐crystal counterparts still lags behind because of the tin instability under ambient conditions during crystal growth and limited reductants to protect the Sn2+ ions from oxidation. Here, the reductant engineering to grow high‐quality tin perovskite single crystals under ambient conditions is studied. Oxalic acid (H2C2O4) serves as an excellent reductant and sacrificial agent to protect Sn2+ ions in methanol due to its suitable redox potential of −0.49 V, and the CO2 as the oxidation product in the gas state can be easily separated from the solution. The FPEA2SnI4 single crystal grown by this strategy exhibits low trap density perovskite surface by constructing an FPEA2PbI4‐FPEA2SnI4 (FPI‐FSI) single crystal heterojunction for X‐ray detection. An improved X‐ray sensitivity of 1.7 × 105 µC Gy−1 cm−2 is realized in the heterojunction device, outperforming the control FPEA2PbI4 counterpart. Tin perovskite has attracted much attention due to its smaller bandgap, while the instability of Sn2+ limits the tin perovskite single crystal growth under ambient conditions. Oxalic acid, serving as a reductant, is proved to be suitable for the solution growth of high‐quality tin perovskite single crystals under ambient air, inhibiting oxidation, reducing defects, and improving device performance.