Preparation and characterization of sputtered aluminum and gallium co-doped ZnO films as conductive substrates in dye-sensitized solar cells

Aluminum and gallium co-doped zinc oxide (GAZnO) films were deposited on borosilicate glass substrates by radio frequency (rf) magnetron technique. The effects of substrate temperature on the structural, optical and electrical properties of the sputtered films were investigated. X-ray diffraction measurement revealed mixed orientations for films prepared at low substrate temperatures, while films prepared at high temperatures were oriented mainly along the (002) direction. Optical transmittance data indicated that the transparency of all the films was above 80% within the visible spectrum, while the electrical resistivity and mobility were improved with increasing substrate temperatures reaching maximum values at 350°C. Finally, using GAZnO films prepared at 300°C and 350°C as transparent conductive substrates in a solar cell sensitized with a metal-free organic dye, light-to-electrical energy conversion efficiency of 3.5 and 3.7% under AM 1.5 irradiation (1000Wm^-2 simulated sunlight) was recorded, respectively.