Electrodeposition of CuIn(Al)Se2-based thin films on various substrates

Abstract

While the electrodeposition of CuInSe2-based compounds have been the topic of many research efforts, effects of the substrate have been rarely addressed in the literature. In the current study, the electrodeposition of CuIn(Al)Se2 thin films on different substrates is performed and effects of the substrate on the morphology and composition of obtained layer are studied. CuIn(Al)Se2 thin films are electrodeposited on different substrates, including copper, stainless steel (SS), and titanium foils as well as fluorine-doped tin oxide (FTO) transparent electrode. Electrodepositions are performed in sulfate solution of Cu2+, Al3+, In3+, and Se4+ ions. The results from cyclic voltammetry (CV), composition and phase analyses indicate that the incorporation of In and Al is a function of the co-deposition potential in cathodic scanning process and the lowest co-deposition potential of − 0.9 V is observed on FTO substrate. Characterizations of deposited films by scanning electron microscopy, energy-dispersive X-ray spectroscopy and X-ray diffraction analysis have also revealed that the deposited films on FTO and Ti substrates contained a layer with high amount of In, Al (In + Al > 7 wt%) and CuIn(Al)Se2 phase with chalcopyrite structure while the deposited film on Cu substrate mainly consists from binary Cu-Se phases. The deposited films on FTO and SS substrates have large particles (> 400 nm) with partly laminar morphology while fine microstructures are obtained for films deposited on Cu (300 nm) and Ti (80 nm) substrates. In addition, by combining the crystallographic information and thermodynamic relations, a method is proposed to predict the favored phase on each support which are in a good agreement with experimental observations.