Doping and Co-Doping of Bandgap-Engineered ZnO Films for Solar Driven Hydrogen Production

Co-doped ZnO:(Al,N) and ZnO:(Ga,N) films were deposited by co-sputtering using radio-frequency magnetron sputtering on F-doped tin-oxide-coated glass. We found that the ZnO:(Al,N) and ZnO:(Ga,N) films exhibited greatly enhanced crystallinity compared to ZnO:N films doped by pure N and deposited under similar conditions. Furthermore, the ZnO:(Al,N) and ZnO:(Ga,N) films showed much higher N-incorporation than ZnO:N films deposited with pure N doping. As a result, the ZnO:(Ga,N) films showed significantly higher photocurrents than ZnO:N doped only by N. The ZnO:(Cu,Ga) films were synthesized by RF magnetron sputtering in O₂ gas ambient at room temperature and then annealed at 500°C in air for 2 hours. We found that the carrier concentration tuning does not significantly change the bandgap and crystallinity of the ZnO:Cu films. However, it can optimize the carrier concentration and thus dramatically enhance PEC response for the bandgap-reduced p-type ZnO thin films.