Front contact optimization for Cu(In,Ga)Se/sub 2/ (sub)modules

The impact of front contact window optimization on module design for different absorber bandgaps is examined, wider bandgaps being simultaneously less demanding of the ZnO IR transparency as well as its sheet conductivity. Based on small area device measurements, examples are given demonstrating the need and deposition method of the high resistive ZnO buffer layer as a function of the CdS buffer layer thickness. Questions concerning the validity of using doped ZnO characteristics of films deposited on glass are addressed. It is shown that the doped ZnO in devices can be potentially quite different from that on glass, some of this difference is tracked to the CdS. This should be accounted for when used in module prediction models.