4.5. Analysis the equivalent circuit electric of AC impedance complex
We used as an investigation tool of this CIGS and CIGS-Si cell (silicon doped cell) the software Zview version 2.2.
These results reflected that there are many in homogeneity phenomena, such as defects, grain boundaries, Cd diffusion into CIGS layer, and so on, around the CdS/CIGS interface [XX]. On the other hand, there are probably small defects and in homogeneities around the ZnO/CdS interface compared with around the CdS/CIGS interface [XX]. To investigate the effect of the CdS layer fitted Cj (CPE around the CdS/CIGS interface) and Cn (capacitance around the ZnO/CdS interface) values of the proposed equivalent-circuit parameters are calculated by using the peak frequency of the semicircle (fmax) and R of the Rp-C or Rp-CPE parallel component as follows:
(7) (8) (9) (10)
However, the above-mentioned terminology applies well when the impedance measurements were taken under illumination and photo generated charge carriers (electrons and holes) remains at donor and acceptor phases. The obtained values of Cj and Cn as a function of CdS /CIGS thickness are shown in Fig. XX. The Cj value increases with increasing CIGS thickness from 0.1 nm (without the Si layer) to 1 nm. This result indicates that depletion layer extended up to the edge of the Si layer and the Cj value depended on the Si layer thickness.