Composition, morphology, and optical properties of CuInSe2 thin films electrodeposited using constant and pulsed potentials

Abstract

CuInSe2 thin films were electrodeposited on conductive glass using potentiostatic (PoED) and pulsed electrodeposition (PuED). One pulse consisted of a step between two potential values: E10-0.9 and E20-0.1 VSCE. Each potential was applied during 10 s. Twenty to 180 pulses were applied. In the case of PoED, -0.9 VSCE were applied during 400 to 3,600 s. The differences in crystallographic structure, morphology, and chemical composition between as-deposited PoED and PuED films were investigated by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and energy dispersive scanning spectroscopy. The presence of secondary phases seemed to be reduced by using PuED. X-ray diffraction showed no significant differences between films prepared by PuED and PoED. Instead, micro-Raman spectroscopy revealed that the chemical composition and homogeneity were improved by pulsing the potential. The thickness of the films increased, and the crystallinity improved as more pulses were applied. For both types of electrodeposition, longer times favored the formation of nearly stoichiometric CuInSe2. For the electrical characterization, the films were annealed in argon and then etched in a KCN solution. KCN etching showed no effect in the film composition. Photoelectrochemical tests and I-V curves confirm p-type conduction. The differences observed in composition, morphology, and optoelectronic properties were attributed to the current profile imposed on the electrode.