The Influence of the n-Side Doping on Metastable Defect Concentrations in Cu(In,Ga)Se2 Evaluated From Space Charge Profiles

In this study, we investigate, through numerical simulations, the influence of the n-side of the Cu(In,Ga)Se2 (CIGS)-based photovoltaic devices on capacitance space charge profiles, with a special emphasis on evaluating metastable defect concentrations. We calculated that for plausible doping level of the CdS buffer ranging from 10
¹⁶
to 10
¹⁸
cm
^-3
, the values of hole concentrations in the absorber delivered by capacitance can be underestimated, and the ZnO/CdS/CIGS devices should not be treated a priori as n
⁺
-p junctions. We showed how this effect can influence the values of metastable defect concentrations extracted from capacitance-voltage (CV) profiles. We indicated that the apparent nonuniformity of experimental CV profiles might be due to an incomplete depletion of the buffer layer. Based on our results, we proposed experiments that can help unveil the correct shallow acceptor and metastable defect concentration in CIGS.