Surface-Enhanced Transparent Conducting P-Type Cui−Ga2o3 Composite Films with High Hole Transport Performance and Stability

CuI is a wide bandgap p-type transparent conductor with promising optoelectronic properties. However, conventional CuI films prepared through the iodination of Cu films exhibit rough surface, poor stability and excessively high hole concentration, hindering its application. Herein, we introduce CuI−Ga2O3 composite films as a substitution to overcome the shortcomings of pure CuI. During the iodination process, Ga2O3 hinders the mobility of CuI grain boundaries, resulting in small grain size and low surface roughness. After the charge re-equilibrium between Ga2O3 and CuI, the hole concentration in the films decreased by an order of magnitude. The interface effect of Ga2O3 at the grain boundaries of CuI, increases the hole mobility by 5 times and the conductivity by 53%. The ultra-wide band gap of Ga2O3 enhances the transmittance of CuI films in short wavelength region. Ga2O3 serves to passivate the grain boundaries of CuI, preventing the oxidation of CuI and the loss of iodine, consequently improving the stability of the films. This work deepens the understanding of the failure and hole transport mechanisms of CuI films.