Development of Superstrate CuInGaSe₂ Thin Film Solar Cells with Low-Cost Electrochemical Route from Nonaqueous Bath

Electrodeposition of Cu­(In,Ga)­Se₂ (CIGS) thin film is an attractive approach for the development of highly efficient low-cost solar cells. This work focuses on the effects of various electrodeposition parameters on the growth and properties of CIGS layers. The films deposited at −0.9 V tend to drive the growth of CIGS favoring (112) crystal orientation, whereas the films deposited at −1.6 V show the orientation along (220)/(204). Interplanar distances corresponding to (112) and (204/220) planes could be observed in the high resolution transmission electron microscopy (HRTEM) images of the respective films, confirming the dependence of the texture on the deposition potential. Films with larger grains could be grown by maintaining higher temperature (130 °C) during the deposition of layers. X-ray photoelectron spectroscopy (XPS) confirmed the presence of Cu⁺, In³⁺, Ga³⁺, and Se^2– valence states in the CIGS layers prepared at −0.9 and −1.6 V. The film deposited at −1.6 V with (220/204) orientation showed high efficiency as compared to the film deposited at −0.9 V with (112) orientation. The observed solar cell parameters, measured under illuminated condition of input power intensity 100 mW/cm², were <i>V</i>_OC = 0.357 V; <i>J</i>_SC = 27 mA/cm², FF = 44, and η = 4.90; and <i>V</i>_OC = 0.460 V, <i>J</i>_SC = 34 mA/cm², FF = 58, and η = 9.07 for the deposition potentials of −0.9 and −1.6 V, respectively<sub>.</sub