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.