The carrier-type of the emerging photovoltaic Sb2Se3 was evaluated for both thin films and bulk crystals via a range of complementary techniques. X-ray photoelectron spectroscopy (XPS), hot probe, Hall effect, and surface photovoltage spectroscopy showed films and crystals synthesized from the Sb2Se3 granulate material to be n-type with chlorine identified as an unintentional n-type dopant via secondary ion mass spectrometry analysis. The validity of chlorine as a dopant was confirmed by the synthesis of intrinsic crystals from metallic precursors and subsequent deliberate n-type doping by the addition of MgCl2. Chlorine was also shown to be a substitutional n-type shallow dopant by density functional theory calculations. TiO2/Sb2Se3 n-n isotype heterojunction solar cells with 7.3% efficiency are subsequently demonstrated, with band alignment analyzed via XPS.
Bibliographical noteFunding Information:
Funding for the work was provided by EPSRC via EP/N014057/1, EP/L01551X/1, EP/P02484X/1, and EP/R513271/1. We acknowledge Diamond Light Source for time on Beamline I09 under Proposal No. SI21431-1. The uses of the UCL Legion, Myriad, and Grace High Performance Computing Facilities (Legion@UCL, Myriad@UCL, and Grace@UCL) are acknowledged in the production of this work. Computational work was also performed on the ARCHER UK National Supercomputing Service, via our membership of the UK’s HEC Materials Chemistry Consortium, funded by EPSRC (EP/L000202). Work at the University of Minnesota was supported by the customers of Xcel Energy through a grant from the renewable development fund. Data files related to the project are available from http://datacat.liverpool.ac.uk/id/eprint/1029 or from the corresponding author.
© 2020 American Chemical Society.