New insights into intrinsic point defects of delafossite CuAlO2 as optoelectronic materials

Delafossite CuAlO2 has great potential in optoelectronics applications. The intrinsic point defects play the decisive roles in the optoelectronic properties and application of CuAlO2. However, there are still disputes about their relevant underlying physical mechanisms at the atomic scale. Here, the formation of intrinsic point defects of CuAlO2 and their effects on optical absorption spectra and electronic structure have been systematically investigated using first‐principles calculations. In oxygen‐rich and oxygen‐poor chemical environments, acceptor‐type defects such as Cu vacancy and Cu substitution on the Al site can spontaneously form and produce p‐type conductivity at room temperature. This is the important physical basis for CuAlO2 to be widely used as transparent conductive oxide films. The shallow acceptor‐type levels produced by Cu substitution on Al site and O vacancy, and the shallow donor‐type levels produced by interstitial Cu, are favorable for the separation of photo‐generated electron–hole pairs, which can be suitable for applications in photocatalysis and photovoltaics. The Cu or Al vacancy can produce delocalized energy band at the top of valence band and pinning Fermi level at the same time, which may make CuAlO2 a degenerate semiconductor and produce local surface plasmon resonance effect. Al substitution on Cu site and interstitial Al or O form complex deep defect energy bands in the forbidden band and produce significant multiband optical absorption in the visible–NIR region. They are expected to become alternative materials for photoluminescence and photoelectric detection. This work demonstrates the importance of intrinsic defect engineering for optimizing optoelectronic properties and thus promoting the discovery of novel optoelectronic materials.