The Defect Chemistry of Emerging, Wide-Bandgap Absorber BiOI

Wide bandgap solar absorbers are seeing significant interest for a variety emerging photovoltaic technologies, from top-layers in tandem cells to single junction devices for indoor applications. V-VI-VII materials have been studied for photocatalysis, but have recently gained interest as “perovskite-inspired” materials (PIMs) for solar absorber applications.^[1]These are materials which stray from the perovskite structure, but share an elemental space, thus keeping the strong antibonding character at the band edges and large dielectric constant, which are associated with the defect tolerance observed in lead halide perovskites.<br/><br/>From the family of bismuth-based absorbers, BiOI has emerged as a leading candidate due to its improved air stability and lack of ultrafast charge-carrier localization, which can pose a challenge for many Bi containing PIMs originating from the reduction in dimensionality.^[1,2,3]However, large concentrations of electron traps have been measured in BiOI thin films, the potential source of poor device performance.^[4]<br/><br/>Therefore, in this project we perform the first, complete investigation into all intrinsic point defect in BiOI at the hybrid DFT level, using the shakenbreak method to thoroughly search the complex defect potential energy surface.^[5] This will allow the identification of harmful defects and guide the development of fabrication processes to reduce their impact.<br/><br/><br/>[1] Y.-T. Huang, S. R. Kavanagh, D. O. Scanlon, A. Walsh, R. L. Z. Hoye, Nanotechnology, 2021, 32, 132004.<br/>[2] D. S. Bhachu, S. J. A. Moniz, S. Sathasivam, D. O. Scanlon, A. Walsh, S. M. Bawaked, M. Mokhtar, A. Y. Obaid, I. P. Parkin, J. Tang and C. J. Carmalt, Chem. Sci., 2016, 7, 4832<br/>[3] A. M. Ganose, M. Cuff, K. T. Butler, A. Walsh, D. O. Scanlon, Chem. Mater., 2016, 28, 1980<br/>[4] S. Lal, M. Righetto, A. M. Ulatowski, S. G. Motti, Z. Sun, J. L. MacManus-Driscoll, R. L. Z. Hoye, L. M. Herz, J. Phys. Chem. Lett., 2023, 14, 6620–6629<br/>[5] I. Mosquera-Lois, S. R. Kavanagh, D. O. Scanlon, A. Walsh, npj Comput. Mater., 2023, 9, 1 —11