Over 500°C stable transparent conductive oxide for optoelectronics

Abstract

Abstract High‐temperature stable transparent conductive oxides (TCOs) are highly desirable in optoelectronics but are rarely achieved due to the defect generation that is inevitable during high‐temperature air annealing. This work reports unprecedented stability in aluminum and fluorine co‐doped ZnO (AFZO) films prepared by pulse laser deposition. The AFZO can retain a mobility of 60 cm2 V−1 s−1, an electron concentration of 4.5 × 1020 cm−3, and a visible transmittance of 91% after air‐annealing at 600°C. Comprehensive defect characterization and first principles calculations have revealed that the offset of substitutional aluminum by zinc vacancy is responsible for the instability observed in aluminum‐doped ZnO, and the pairing between fluorine substitution and zinc vacancy ensures the high‐temperature stability of AFZO. The utility of AFZO in enabling the epitaxial growth of (AlxGa1−x)2O3 film within a high‐temperature, oxygen‐rich environment is demonstrated, facilitating the development of a self‐powered solar‐blind ultraviolet Schottky photodiode. Furthermore, the high‐mobility AFZO transparent electrode enables perovskite solar cells to achieve improved power conversion efficiency by balancing the electron concentration‐dependent conductivity and transmittance. These findings settle the long‐standing controversy surrounding the instability in TCOs and open up exciting prospects for the advancement of optoelectronics.

Keywords

• aluminum and fluorine co‐doped ZnO
• high temperature
• Schottky photodiodes
• solar cells
• stability mechanism
• transparent conductive oxides