Influence of Al/Cu thickness ratio and deposition sequence on photoelectric property of ZnO/Al/Cu/ZnO multilayer film on PET substrate prepared by RF magnetron sputtering

Abstract ZnO/Al/Cu/ZnO multilayer films were deposited on flexible polyethylene terephthalate (PET) substrates by radio frequency (RF) magnetron sputtering. The overall thickness of the intermediate Al and Cu metal layers maintained at 8 nm. The four different Al/Cu thickness ratios were 7:1, 6:2, 5:3 and 4:4. Other four reference samples were prepared by using the same process, i.e. ZnO single-layer film, ZnO/Al 8 (8-nm-thick Al layer, the same below)/ZnO, ZnO/Cu 8 /ZnO and ZnO/Cu 2 /Al 6 /ZnO multilayer films. The effects of Al/Cu thickness ratio and deposition sequence of Al and Cu layers were investigated. The results revealed that with the increase of Cu layer thickness, sheet resistance of the multilayer film decreased, while transmittance increased first and then decreased. The ZnO/Al 6 /Cu 2 /ZnO multilayer film with a sheet resistance of 108 Ω/sq and an average visible transmittance of 84.73% had the optimum overall photoelectric property, being confirmed by the highest figure of merit of 1.77 × 10 –3 Ω –1 . Furthermore, ZnO/Cu 2 /Al 6 /ZnO and ZnO/Al 6 /Cu 2 /ZnO multilayer films exhibited almost the same average visible transmittance and sheet resistance, implying that the deposition sequence of Al and Cu layers has little influence on photoelectric properties. It is demonstrated that ZnO/Al/Cu/ZnO multilayer flexible films have great potential in various fields.