All-sputtered 14% CdS∕CdTe thin-film solar cell with ZnO:Al transparent conducting oxide

Radio-frequency (rf)-sputtered $\mathrm{Al}$ -doped $\mathrm{ZnO}$ was used as the transparent front contact in the fabrication of high efficiency superstrate configuration $\mathrm{CdS}∕\mathrm{CdTe}$ thin-film solar cells. These cells had $\mathrm{CdS}$ and $\mathrm{CdTe}$ layers also deposited by rf sputtering at $250°\mathrm{C}$ with the highest processing temperature of $387°\mathrm{C}$ reached during a post-deposition treatment. The devices were tested at National Renewable Energy Laboratory and yielded an efficiency of $14.0\%$ , which is excellent for a $\mathrm{CdTe}$ cell using $\mathrm{ZnO}$ and also for any sputtered $\mathrm{CdTe}$ solar cell. The low-temperature deposition process using sputtering for all semiconductor layers facilitates the use of $\mathrm{ZnO}$ and conveys significant advantages for the fabrication of more complex multiple layers needed for the fabrication of tandem polycrystalline solar cells and for cells on polymer materials.