Al and F codoped ZnO by a novel co-spray deposition technique for solar cells applications

ZnO was successfully synthesized by a novel co-spray deposition technique. Two solutions were prepared and sprayed through two spray heads. In one solution, Zn(O₂CCH₃)₂ (Zn precursor) and AlCl₃ (Al precursor) were dissolved in a mixture of deionized water and ethanol. In another solution, NH4F (F precursor) was dissolved in the same mixture. The deposition was carried out at 500°C on soda-lime glass in air. Compared to Al-doped or F-doped ZnO, Al and F codoped ZnO resulted in much lower sheet resistance. The lowest sheet resistance obtained so far is below 55 Ω/sq from solutions with 0.6 at.% Al and 55 at.% F, respectively, after vacuum annealing at 400°C for 1 h. The average transmittance of Al and F codoped ZnO is above 80% in the visible range. The effects of dopant concentrations in the starting solutions on the electrical, structural, and optical properties of Al and F codoped ZnO were also investigated.