Multimodal characterization of solution-processed Cu3SbS4 absorbers for thin film solar cells

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 cm⁻¹), 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.