8:30 AM - EL04.10.03
Dopability in Antimony Selenide—Suppressing Amphoteric Antisites
Christopher Savory1,Laurie Phillips2,Jonathan Major2,David Scanlon1
University College London1,University of Liverpool2
With the global demand for energy increasing year on year, diversification beyond current technologies and materials is crucial to meeting this demand by accessing more sustainable materials in a wider variety of device architectures and applications. In photovoltaics, while silicon is the dominant technology, its poor absorption puts upper bounds on device thinness, while established ‘thin-film’ materials such as CdTe allow strong absorption from nanometre-thin films and flexible devices but suffer from toxicity and low abundance of constituent elements.1,2
Antimony Selenide, on the other hand, is a highly promising candidate chalcogenide photovoltaic absorber, possessing a very high absorption coefficient, near-ideal band gap and relatively abundant constituents. Solar cells utilising it as the absorber layer are nearing 10% in efficiency,3 and the pseudo-1D nature of the material, with van der Waals interactions, has been highlighted as a potential reason for benign grain boundaries.4 Our recent theoretical work, however, has found that despite a high dielectric constant and a ns2 ‘lone-pair’ cation configuration, both characteristics that have been associated with the concept of defect tolerance, Sb2Se3 possesses multiple low formation energy intrinsic defects with mid-gap transition levels that could severely hinder future improvements in open circuit voltage.5
In this study, we discuss these hybrid density functional theory calculations on the intrinsic defects of Sb2Se3 with focus on examining how the amphoteric behaviour of selenium allows for such low formation antisite defects, which may pin the Fermi level. Further, we examine the carrier capture behaviour of these defects and which defect levels may be responsible for the trap states seen in experimental DLTS measurements. Finally, we have also performed calculations on numerous extrinsic dopants to assess possible routes to doping in Sb2Se3, including passivation of deep intrinsic levels, and, in collaboration with colleagues at the University of Liverpool, potential contaminants that may affect current and future devices. Through these results, our study examines the specific effects at play within Sb2Se3 but also explores the consequences on the applicability of ‘defect tolerance’ within post-transition metal chalcogenide materials.
(1) Haegel, N. M.; Margolis, R.; Buonassisi, T.; Feldman, D.; Froitzheim, A.; Garabedian, R.; Green, M.; Glunz, S.; Henning, H.; Holder, B.; Kaizuka, I.; Kroposki, B.; Matsubara, K.; Niki, S.; Sakurai, K.; Schindler, R. A.; Tumas, W.; Weber, E. R.; Wilson, G.; Woodhouse, M.; Kurtz, S. Science (80-. ). 2017, 356 (6334), 141.
(2) Peter, L. M. Philos. Trans. A. Math. Phys. Eng. Sci. 2011, 369, 1840.
(3) Li, Z.; Liang, X.; Li, G.; Liu, H.; Zhang, H.; Guo, J.; Chen, J.; Shen, K.; San, X.; Yu, W.; Schropp, R. E. I.; Mai, Y. Nat. Commun. 2019, 10, 125.
(4) Zhou, Y.; Wang, L.; Chen, S.; Qin, S.; Liu, X.; Chen, J.; Xue, D.-J.; Luo, M.; Cao, Y.; Cheng, Y.; Sargent, E. H.; Tang, J. Nat. Photonics 2015, 9 (6), 409.
(5) Savory, C. N.; Scanlon, D. O. J. Mater. Chem. A 2019, 7 (17), 10739.