All sputtered 14% CdS/CdTe device with ZnO:Al front contact

An Al-doped ZnO front contact was successfully used for the first time for the fabrication of high efficiency CdS/CdTe thin-film solar cells. The ZnO:AI films were deposited on aluminosilicate glass by RF sputtering from a ZnO:Al/sub 2/O/sub 3/ target. The ZnO:AI film has /spl sim/95% average transmission in the visible spectrum with /spl sim/3 ohm/square sheet resistance. The CdS and CdTe thin films were also deposited by RF sputtering and devices were completed with a vapor CdCl/sub 2/ treatment and evaporated Cu/Au back contacts. The highest processing temperature was 387/spl deg/C, reached during the vapor CdCl/sub 2/ treatment. The devices were tested at NREL with efficiency of 14.0% which is a record for an all-sputtered CdS/CdTe solar cell. The ZnO-based cell had J/sub SC/ of 23.6 mA/cm/sup 2/ compared to 20.7 mA/cm/sup 2/ for our recent NREL-tested 12.6% cell on a commercial soda-lime-glass/SnO/sub 2/:F substrate. Other parameters of the 14% ZnO based cell are: FF = 73.25% and V/sub OC/ = 814 mV. The improved performance is almost entirely due to higher current because of better optical and electrical properties of ZnO:Al TCO. We report also on the relative stability between devices on SnO/sub 2/:F and ZnO:Al TCO, under one-sun light soak at V/sub OC/.