Copper iodide and oxide semiconductor thin films patterned by spray-spin coating for fabricating complementary inverters: Improving stability with passivation layers

Abstract

Recently, copper iodide (CuI) has been studied as a solution-processed p-type semiconductor owing to its high hole mobility and low-temperature processability. With the development of the field in this solution-processed inorganic semiconductor, it has become increasingly necessary to integrate the p-type thin-film transistors (TFTs) into a complementary inverter using a simple solution-based patterning method. However, compared to the n-type counterpart, it remains a challenge to pattern the p-type inorganic TFTs while maintaining reliable performances. In this study, Zn-doped CuI (Zn:CuI) were patterned in a simple manner by combining spin and spray coating, namely “spray-spin coating,” to fabricate p-type TFTs. The device stability of the spray-spin-coated Zn:CuI TFTs was ensured by treating hydrophobic fluoropolymer, CYTOP, as a passivation layer. Owing to the blocking of oxygen penetration at the CYTOP layer, which was confirmed by the chemical binding energy states of the Zn:CuI thin film, the resulting devices exhibited enhanced electrical characteristics while maintaining low off-state current and normal threshold voltage. Finally, via spray-spin coating, complementary inverters comprising n-type In2O3/ZnO bilayer and p-type Zn:CuI semiconductors were successfully fabricated on a single wafer, demonstrating a robust switching operation.