Experimental and computational study of Cu2FeSnS4: An emerging quaternary semiconductor

Abstract

The quaternary semiconductor Cu2FeSnS4 (CFTS) has attracted attention of the research community due to its optical and electrical properties, earth abundance and non-toxicity. CFTS powder has been successfully synthesized using solvothermal technique. X-ray diffraction peaks and Raman spectra confirm structural formation of the compound, and XPS studies determine the oxidation states of Cu, Fe, Sn and S to be +1, +2, +4 and −2 respectively. The scanning electron microscopy images show nanosheet array-like morphology and the stoichiometry ratio of 2:1:1:4 for Cu, Fe, Sn and S respectively is obtained from EDS measurements. Direct band gap of 1.52 eV has been estimated using the Tauc plot. The experimental findings have been supported computationally using density functional theory (DFT) based calculations performed within quantum espresso (QE) software. The stannite phase is observed to be the ground state and is in accordance with the experimental observation. The total density of states (DOS) and projected DOS show the contribution of each elemental species in valence and conduction bands. A direct band gap of 1.51 eV obtained from HSE06 hybrid functional is in good agreement with the Tauc plot result. Further, the cation defect formation calculations show that Cu vacancy is most likely to be formed among the cations. The computationally obtained absorption spectra confirms the application of CFTS as absorber layer in a solar cell. The electrical study of the p-CFTS and n-CdS junction is carried out using J-V response. The calculated ideality factor, series resistance and power conversion efficiency show promising application in photovoltaic industry. The present work fills the existing gap in the published literature of a systematic experimental and computational study of CFTS semiconductor, which has application in varied fields.