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Core-Levels, Band Alignments, and Valence Band States in CuSbS 2 for Solar Cell Applications

DOI: 10.1021/acsami.7b14208 DOI Help

Authors: Thomas J. Whittles (University of Liverpool) , Tim D. Veal (University of Liverpool) , Christopher N. Savory (University College London) , Adam W. Welch (National Renewable Energy Laboratory) , Francisco Willian De Souza Lucas (National Renewable Energy Laboratory) , James T. Gibbon (University of Liverpool) , Max Birkett (University of Liverpool) , Richard J. Potter (University of Liverpool) , David O. Scanlon (University College London; Diamond Light Source) , Andriy Zakutayev (National Renewable Energy Laboratory) , Vinod R. Dhanak (University of Liverpool)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acs Applied Materials & Interfaces

State: Published (Approved)
Published: November 2017

Abstract: The earth-abundant material CuSbS2 (CAS) has shown good optical properties as a photovoltaic solar absorber material, but has seen relatively poor solar cell performance. To investigate the reason for this anomaly, the core-levels of the constituent elements, surface contaminants, ionization potential, and valence band spectra are studied by x-ray photoemission spectroscopy (XPS). The ionization potential and electron affinity for this material (4.98 eV and 3.43 eV) are lower than for other common absorbers, including CuInxGa(1-x)Se2 (CIGS). Experimentally corroborated density functional theory (DFT) calculations show that the VBM is raised by the lone pair electrons from the antimony cations contributing additional states when compared with indium or gallium cations in CIGS. The resulting conduction band misalignment with CdS is a reason for the poor performance of cells incorporating a CAS/CdS heterojunction, supporting the idea that using a cell design analogous to CIGS is unhelpful. These findings underline the critical importance of considering the electronic structure when selecting cell architectures that optimize open-circuit voltages and cell efficiencies.

Journal Keywords: CuSbS2; copper antimony sulfide; XPS; DFT; thin film solar cells; band alignments; density of states

Subject Areas: Materials, Energy

Technical Areas: