Fabrication of transparent conducting films composed of In³⁺ doped CuS and their application in flexible electroluminescent devices

Transparent conductive films composed of CuS were formed by wet deposition on PET at room temperature followed by annealing at 100 °C for 1 hour. The resistance of the films was tuned by doping with In³⁺. A decrease of over an order of magnitude of the sheet resistance was obtained, from 1721 Ω sq^-1 for undoped CuS film to 109 Ω sq^-1 for In³⁺ doped. Transparency of the conducting films could be tuned by an appropriate selection of reaction time and In³⁺ concentration. It was found that films containing 10 mol% of In³⁺ ions after a reaction duration of 24 hours have a sheet resistance of ∼270 Ω sq^-1 and a transparency of ∼80%. The fabricated films are characterized by excellent adhesion to the PET substrate and are shown to be suitable for use as transparent conducting electrodes (TCE) in flexible electroluminescent (EL) devices.