PNNL

Abstract

The most efficient inorganic thin film chalcogenide-based solar cells use CdTe or CuInGaSe2 (CIGS) as absorber layers, which rely on toxic (Cd) and/or scarce elements (In, Te). The desire for more sustainable solar cells has led to the development of Earth abundant and non-hazardous chalcogenide absorbers. Cu3SbS4 (famatinite) is a promising Earth abundant p-type semiconductor that has a low direct band gap (0.9–1.05 eV), is a superabsorber (absorption coefficient 104–105 cm1), and has potential in low-cost, thin-film solar cells. Although these properties make the Cu3SbS4 phase stand out as a promising material for photovoltaics, to date Cu3SbS4 solar cells have only achieved low efficiencies. In this study, we demonstrate a method for synthesizing Cu3SbS4 nanocrystals and formation of thin-films by coating nanocrystal precursors onto substrates. Optical, structural, and chemical state characterization were performed before and after thermal processing of the Cu3SbS4 films. A detailed experimental analysis of the bulk and surfaces of the Cu3SbS4 absorber films indicate that phase stability and preferential copper oxidation at the surface may limit device performance for Cu3SbS4 based solar cells. These findings may provide significant insight on how to improve Cu3SbS4 based solar cell performance by controlling processing conditions. This research was funded by the United States National Science Foundation – Scalable Nanomanufacturing program (Grant CBET-1449383). A portion of this research was performed at the Northwest Nanotechnology Infrastructure, a member of the National Nanotechnology Coordinated Infrastructure, which is supported by the National Science Foundation (Grant ECCS- 1542101). The acquisition of the OSU Titan TEM was supported by the National Science Foundation via the Major Research Instrumentation (MRI) program under Grant No. 1040588, the Murdock Charitable Trust, and the Oregon Nanoscience and Microtechnologies Institute (ONAMI). XANES spectra were obtained through an approved program user proposal at the Advanced Light Source, which is a DOE Office of Science User Facility under contract no. DE-AC02-05CH11231. The ALS approved program user proposal beam time was obtained through the chemical imaging initiative, an LDRD program at PNNL. We acknowledge Trey Diulus and Dr Igor Lyubinetsky for their assistance with the XPS experiments.