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;