Metal Oxides produced by Hollow Cathode Sputtering, their Utility in Thin Film Photovoltaics, and Results for AZO

摘要

An R&D-scale hollow cathode sputtering (HCS) system has been designed and built at NJIT. It operates in reactive mode using metal targets and can deposit virtually any metal oxide. We survey the use of metal oxide layers in thin film PV and report the preparation by HCS of several oxides including ZnO, ZnO:Al (AZO), Zn_xSn_yO, Cd_xSn_yO, and Cu_(2-x)O. Oxynitrides have also been prepared. For AZO, an excellent electron mobility of 53.4 cm~2/Vs has so far been achieved, close to a world record for an as-deposited, sputter-based AZO layer. Cu_(2-x)O layers have been successfully utilized as a back contact in CdTe solar cells. Work is under way to prepare the entire front stack of CdTe solar cells, namely TCO/HRT/buffer, by hollow cathode sputtering.