Optical and electrical characterization of CIGS thin films grown by electrodeposition route

In this paper, the electrochemical impedance spectroscopy was handled to study the electrochemical attitude of quaternary alloy Cu (In, Ga) Se2/Na2SO4 electrolyte interface. Subsequently, an annealing treatment was performed at various temperatures (250–400 °C). The material features of Cu (In, Ga) Se2 films are controlled by the percentage of gallium content. XRD studies showed three favorite orientations along the (1 1 2), (2 2 0), and (1 1 6) planes for all samples. The morphological and chemical composition studies exhibited Ga/(Ga + In) ratio ranging from 0.27 to 0.32 and RMS surface roughness were in the range 54.2–77.8 nm respectively. The optical band gap energy of the CIGS alloys can be strongly controlled by adjusting gallium and indium concentrations. EIS measurement has been modeled by using an equivalent circuit. Mott–Schottky plot illustrates p-type conductivity of CIGS film with a carrier concentration around 1016 cm−3, a flat band potential Vfb ranging from −0.68 V to −0.57 V, and depletion layer thickness rises from 0.24 to 0.36 μm.