Selenization of electrochemically synthesized copper-indium layers from non-aqueous solution for solar cell application

A simple two-step, electrodeposition of copper-indium (Cu-In) intermetallic alloy thin films followed by selenization process was employed for the synthesis and development of CuInSe2 (CIS) thin film solar cells (TFSC). The co-deposition of Cu and In in ethylene glycol at 130 °C was studied using the cyclic voltammetry (CV) to obtain a stable Cu-In phase. A wide window of deposition potentials from −0.7 V to −1.5 V versus Ag/AgCl reference electrode was optimized. Three different potentials, −0.7 V, −1.0 V and −1.3 V are chosen to deposit the Cu-In intermetallic alloy thin films, which were further selenized in controlled selenium ambient at 400 °C. The selenization effect is studied extensively on structural, morphological, optical and compositional properties of selenized Cu-In (CIS) thin films. Polycrystalline CIS layers with tetragonal crystal structure are obtained upon selenization of Cu-In thin films. Three prominent reflections of CIS, (112), (204/220) and (312/116) are exhibited in all selenized Cu-In layers. Additional secondary phases of CuxSe1-x are attributed for the layers grown at −0.7 and −1.0 V. Compact and void-free surface morphology with particle size ∼1-2 μm was observed for all selenized samples. The selenized Cu-In layer sample deposited at −1.3 V measure ∼1.06 eV energy band gap with polycrystalline tetragonal chalcopyrite crystal structure of CIS. The photoelectrochemical measurement confirms the growth of p-type material. A selenized Cu-In layer deposited at −1.3 V with CdS window layer measured power conversion efficiency 5.44%.