Reversible Oxidative p-Doping in 2D Tin-Based Halide Perovskite Transistors

Tin-based halide perovskites exhibit excellent electrical properties, making them promising semiconducting materials for various optical and electrical devices. Despite significant advances, their susceptibility to environmental factors such as oxygen and moisture often limits reliable device operation [1]. Two-dimensional tin-based perovskites show better stability than their three-dimensional counterparts while maintaining good electrical properties [2], but they are still not entirely stable. Therefore, understanding atmospheric effects and the underlying mechanism is crucial for developing stable and reliable tin-based perovskite devices. However, the intricate mechanisms are yet to be fully elucidated.<br/>In this study, we investigated the effects of ambient air exposure on phenethylammonium tin iodide ((PEA)₂SnI₄) perovskite field effect transistors (FETs) [3]. Upon exposure to ambient air for minutes, we observed a significant p-shift (+15.8 V in the threshold voltage) and enhanced p-type conduction. Remarkably, successively exposing (PEA)₂SnI₄ FETs to vacuum conditions displays a gradual recovery of the electrical properties to their pristine states. The X-ray photoelectron spectroscopy and X-ray diffraction studies revealed negligible degradation, such as Sn²⁺-to-Sn⁴⁺ oxidation or perovskite decomposition, under successive air and vacuum conditions. Additional electrical measurements identified oxygen in ambient air as the primary agent driving this reversible doping phenomenon.<br/>To identify the mechanism of reversible p-doping, we did a theoretical study using density functional theory. We found that oxygen molecules occupying interstitial sites within the perovskite lattice can act as electron acceptors which induce p-doping without causing degradation. Both experimental and theoretical results support that reversible p-doping phenomena occur when exposing the perovskites to ambient air for several minutes. Our findings will advance the understanding of environmental effects on tin-based perovskites, offering insights for improving the reliability and stability of perovskite devices.<br/><br/>References<b> </b><br/>[1] L. Lanzetta, T. Webb, N. Zibouche, X. Liang, D. Ding, G. Min, R. J. E. Westbrook, B. Gaggio, T. J. Macdonald, M. S. Islam, S. A. Haque, <i>Nat Commun</i>, 12, 2853 (2021).<br/>[2] Y. Liao, H. Liu, W. Zhou, D. Yang, Y. Shang, Z. Shi, B. Li, X. Jiang, L. Zhang, L. N. Quan, R. Quintero-Bermudez, B. R. Sutherland, Q. Mi, E. H. Sargent, Z. Ning, <i>J. Am. Chem. Soc</i>. 139, 6693 (2017).<br/>[3] Y. Kim, J. Woo, Y.-K. Jung, H. Ahn, I. Kim, Y. Reo, H. Lim, C. Lee, J. Lee, Y. Kim, H. Choi, M.-H. Lee, J. Lee, S. D. Stranks, H. Sirringhaus, Y.-Y. Noh, K. Kang, and T. Lee, <i>ACS Energy Letters</i>, 9, 1725 (2024).