Phase pure CuSbS2 thin films by heat treatment of electrodeposited Sb2S3/Cu layers

Abstract

In this work, we report the fabrication of CuSbS2 (CAS) thin films from Sb2S3/Cu multilayer developed by using electrodeposition. Sb2S3 thin films of approximately 250 nm were deposited by pulse electrodeposition from a bath containing SbCl3 and Na2S2O3 precursors onto which Cu was electrodeposited. In order to optimize the formation of pure chalcostibite phase of CuSbS2, the thickness of Cu layer was varied from 55 to 130 nm. The Sb2S3/Cu multilayer was heat treated at 250 °C under N2/S atmosphere for 30 min for its conversion into CuSbS2 and to enhance the crystallinity. XRD spectra showed orthorhombic phase for all CAS samples. Raman analysis confirmed that the sample with 100 nm of Cu thickness has the highest phase purity. SEM image demonstrated a homogeneous thin film with spherical grains. The chemical states of the elements in the phase pure CuSbS2 film were obtained from X-ray photoelectron spectroscopy evidencing the oxidation states as Cu+Sb3+S2−. The optical characterization demonstrated a band gap of 1.45 eV. Furthermore, the results showed that the CuSbS2 thin film is photosensitive and p-type. The energy level band diagram reaffirms its potential as a good absorber layer in thin film solar cells with suitable charge transport pathways.