Buried pn homojunction in Cu(InGa)Se/sub 2/ solar cells formed by intentional Zn doping

In this study, we tried intentional doping and fabrication of a pn homojunction at the surface of the Cu(InGa)Se/sub 2/ (CIGS) solar cell by Zn evaporation. For Zn doping of the CIGS layer, Zn was evaporated after CIGS formation and we successfully demonstrated a potential improvement in cell performance by this technique. Furthermore, Zn diffusion into the CIGS film was investigated by secondary ion mass spectroscopy (SIMS). A conductivity-type conversion from p-type to n-type was studied by the measurement of the cross-sectional electron beam-induced current (junction EBIC: JEBIC) and the spectral response of solar cells. A conversion efficiency of 11.5 % has been achieved using the Zn-doped CIGS layer without a buffer layer and by the formation of a pn homojunction in the CIGS absorber.