Synthesis and Application of Electronic Oxides for Solar Energy

Plasma-enhanced chemical vapor deposition (PECVD) is being developed as a flexible coating technology for a variety of oxides. In this paper we discuss the synthesis of transparent conducting oxides (TCOs), insulating oxides and electrochromic oxides. Tin oxide was synthesized using mixtures of SnCl 4 and O 2 . By proper control of processing conditions the resistivity of this material may be varied from 10 -3 5 Ω-cm. Films of varying resistivity were employed as buffer layers in CdS/CdTe solar cells. Preliminary device results have demonstrated that integration of a tin oxide buffer layer was very beneficial for cell performance. In addition, we demonstrate the PECVD synthesis of WO 3 from WF 6 /O 2 /H 2 /Ar mixtures. The plasma process space that yielded adherent, transparent tungsten oxide was established. The deposited films were both amorphous and reversibly electrochromic. High temperature annealing above 400°C converted the films into a polycrystalline state.