Fabrication of Buffer-Window Layer System for Cu(In, Ga)Se2 Thin Film Devices by Chemical Bath Deposition and Sol–Gel Methods

Recently, nontoxic fabrication for Cu(In, Ga)Se 2 thin films gained increasing popularity. In this work, chemical bath deposition and Sol–gel methods were utilized in the fabrication of an environmentally buffer-window (ZnS-ZnO/ZnO:Al) layer system for Cu(In, Ga)Se 2 thin film devices. The influences of conditions like annealing temperature, coating times, and Al-doping amount were investigated. The surface morphology and optical properties illustrated a compact and uniform ZnS film with a band-gap of 3.78, which can be a good alternative to CdS film. Resistivity of 0.35 Ω·cm for the ZnO/ZnO:Al film was achieved by the ideal condition of 9 coating times and 5 Al-doping amounts. A cross-sectional view of the complete Cu(In, Ga)Se 2 thin film was obtained, and the structure status was analyzed.