Surface-enhanced p-type transparent conducting CuI−Ga2O3 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−Ga 2 O 3 composite films as a substitution to overcome the shortcomings of pure CuI. During the iodination process, Ga 2 O 3 hindered the mobility of CuI grain boundaries, resulting in small grain size and low surface roughness. After the charge re-equilibrium and low-energy carrier filtering at the interface between Ga 2 O 3 and CuI, the hole concentration in the films decreased by an order of magnitude. Due to the interface effect of Ga 2 O 3 at the grain boundaries of CuI, the hole mobility increased by 5 times, and the conductivity improved by 53%. The ultra-wide band gap of Ga 2 O 3 enhanced the transmittance of CuI films in short wavelength region. Ga 2 O 3 served 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 will deepen the understanding of the failure and hole transport mechanisms of CuI films. • The second phase Ga 2 O 3 inhibits the movement of CuI grain boundaries. • Ga 2 O 3 reduces the surface roughness of CuI films. • CuI−Ga 2 O 3 films have lower hole concentration, higher conductivity and hole mobility. • CuI−Ga 2 O 3 films exhibit better stability in ambient than pure CuI films. [ABSTRACT FROM AUTHOR]