Numerical investigations of the impact of buffer germanium composition and low cost fabrication of Cu ₂O on AZO/ZnGeO/Cu ₂O solar cell performances

Abstract

Numerical simulations of AZO/Zn _{1− x} Ge _x O/Cu ₂O solar cell are performed in order to model for the first time the impact of the germanium composition of the ZnGeO buffer layer on the photovoltaic conversion efficiency. The physical parameters of the model are chosen with special care to match literature experimental measurements or are interpolated using the values from binary metal oxides in the case of the new Zn _{1− x} Ge _x O compound. The solar cell model accuracy is then confirmed thanks to the comparison of its predictions with measurements from the literature that were done on experimental devices obtained by thermal oxidation. This validation of the AZO/Zn _{1− x} Ge _x O/Cu ₂O model then allows to study the impact of the use of the low cost, environmental friendly and industrially compatible spray pyrolysis process on the solar cell efficiency. To that aim, the Cu ₂O absorber layer parameters are adjusted to typical values obtained by the spray pyrolysis process by selecting state of the art experimental data. The analysis of the impact of the absorber layer thickness, the carrier mobility, the defect and doping concentration on the solar cell performances allows to draw guidelines for ZnGeO/Cu ₂O thin film photovoltaic device realization through spray pyrolysis.