Industrial high-rate (∼14 nm/s) deposition of low resistive and transparent ZnOx:Al films on glass

The results presented in this paper show that highly conductive and transparent ZnO
_x
:Al films can be grown on glass by a high throughput industrial CVD process at atmospheric pressure. Amorphous silicon p-i-n solar cells have been grown on as deposited ZnO
_x
:Al films in order to demonstrate the suitability of this material as front contact for thin silicon film solar cells. Aluminum doped ZnO
_x
(ZnO
_x
:Al) films have been deposited on glass in an in-line industrial-type reactor by a metalorganic chemical vapor deposition process at atmospheric pressure. Tertiary-butanol has been used as oxidant for diethylzinc and trimethylaluminium as dopant gas. ZnO
_x
:Al films can be grown at very high deposition rates of ~ 14 nm/s for a substrate speed from 150 mm/min to 500 mm/min. The electrical, structural (crystallinity and morphology) and optical properties of the deposited films have been characterized by using Hall, four point probe, X-ray diffraction, atomic force microscope and spectrophotometer, respectively. All the films have c-axis, (002) preferential orientation and good crystalline quality. ZnO
_x
:Al films are highly conductive (R <; 9 Ohm/sq, for a film thickness above 1300 nm) and transparent in the visible range (>; 80%). Amorphous silicon p-i-n solar cells have been grown on as deposited ZnO
_x
:Al films, without optimizing the surface texturing of ZnO
_x
:Al films to enhance light scattering. An initial efficiency of approximately 8% has been achieved.