A. Impedance spectra (SCAPS1D) and Equivalent circuit (EQC Zview software fitting)
First, the equivalent circuit of CIGS and CIG-SI solar cells obtained by impedance analysis is the excellent characteristics. In general, an equivalent circuit of simple heterojunction materials consists of three elements, namely, a series resistance (Rs) and Rbulck, parallel circuit of parallel resistance (Rp), and constant capacitance (C) or “capacitance-like element” called a constant phase element (CPE). These models are shown in Fig. 6. A spatial in homogeneity, probably originating from the grain boundaries in the absorber layer, made it necessary to introduce a CPE (constant phase elements). In general, non-ideal behavior originates from a distribution in the current density due to material in homogeneity For example; a CPE is often used in DSC impedance models in place of a capacitance-like element to compensate for in homogeneity in the TiO2/dye interface [17, 18]. The impedance of CPE (ZCPE) is defined by CPE index “p” (CPE-p) and CPE constant “T” (CPE-T) as follows;