The effect of citric acid and selenization onto electrochemically deposited Copper-Indium thin films for solar cell applications

Abstract

Copper Indium diselenide (CISe) layers have been synthesized via two stage processes; electrodeposition of Copper-Indium (Cu-In) and selenization. The effect of complexing agent, citric acid (CA) was studied on the growth of Cu, In and Cu-In layers. Polycrystalline Cu-In layers were electrodeposited from aqueous bath at −0.85V versus Ag/AgCl reference electrode. The structural, optical, morphological, compositional, photoelctrochemical and optoelectronic properties for Cu-In layer and selenized Cu-In layers are studied. Three prominent reflections of tetragonal crystal structure of CISe, (112), (204/220) and (312/116) were exhibited in selenized layers. Nearly uniform, void-free surface morphology was observed in selenized samples. Upon selenization of Cu-In layers prepared with 0.1M CA produced stoichiometric CISe thin films. The energy band-gap values are estimated between 1.05eV to 1.18eV. Photoelectrochemical cell measurement revealed the growth of p-type and n-type conductivity of CISe thin films. The peaks related to chalcopyrite CISe and ordered defect compound are observed in Raman analyses. The superstrate solar cell structure prepared with selenized Cu-In layer deposited in presence of 0.1M CA measured 4.05% efficiency. The values of Rs, 7.42Ω-cm2, 0.94Ω-cm2 and G, 1.01mS/cm2 10.25mS/cm2 were calculated under dark and illuminated condition, respectively. We believe that the measured efficiency is low; however the further improvement is possible by optimizing the surface treatment conditions.