Combinatorial study of Sn-Ti-W-O transparent conducting oxide thin films for photovoltaic applications

a combinatorial study of transparent conducting oxide thin films based on SnO2–TiO2-WO3 phase space is reported. These multinary oxide films were fabricated by magnetron reactive co-sputtering of tin monoxide (SnO), titanium (Ti) and tungsten (W) targets. SnO2–TiO2-WO3 film compositions with Ti/Sn ratio (0.02 – 0.12) and W/(Ti+Sn) ratio (0.02 – 0.25) were explored. The effect of oxygen partial pressure on composition, structure and optical properties was evaluated. High optical transparency above 80% across the visible spectrum was obtained for sputtered ternary SnO2-TiO2 oxide films for oxygen partial pressure >19.4%. A positive correlation between optical bandgap and Ti/Sn ratio was observed. However, optical properties deteriorated as Ti-content increased in the as-deposited SnO2-TiO2-WO3 films. All studied as-deposited SnO2-TiO2-WO3 thin films were found to be highly resistive. X-ray diffraction data indicated no long-range structural order.