Optimization of Al-doped ZnO window layers for large-area Cu(InGa)Se2-based modules by RF/DC/DC multiple magnetron sputtering

In this report, a comparative study of physical propel ties of the multilayered ZnO:Al films prepared by a combination of RF and DC magnetron sputtering is presented. It has been found that a RF/DC/DC trilayered system consisting of a thin RF sputtered ZnO:Al bottom layer with two identical DC-sputtered ZnO:Al layers deposited with a low DC current improved the physical propel-ties when compared to those of the ZnO film of the baseline condition, [DC(2.0 A, thickness of about 6500 Angstrom) monolayer]. The sheet resistance and transmittance of the highest quality ZnO film deposited with the RF(600 Angstrom)/DC(1.2 A, thickness of 4200 Angstrom)/DC(1.2 A, thickness of 4200 Angstrom) sputtering condition were found to be 10 Omega/sq and 85% in the wavelength range of 350-1400 nm, respectively. With the newly improved transparent-conductive-oxide (TCO) window, Cu(InGa)Se-2 (CIGS) modules (aperture area = 50 cm(2)) have been fabricated, and marked improvement in fill factor (FF) (+8%) and efficiency (+12%) have been obtained when compared to those of the ZnO:Al deposited under the baseline condition. The average efficiency of the above CIGS modules was found to be 11.1%.