Heteroepitaxial growth of Cu2O films on Nb-SrTiO3 substrates and their photovoltaic properties

In this paper, p-type Cu2O thin films have been epitaxially grown on n-type semiconducting (001) oriented Nb-SrTiO3 (NSTO) substrates with different Nb doping concentration by pulsed laser deposition technique. X-ray diffraction and high resolution transmission electron microscopy reveal a cube-on-cube epitaxial relationship between Cu2O and NSTO. It is found that the deposition temperature, the thickness of Cu2O films and the Nb doping concentration of NSTO substrates have critical impact on the photovoltaic (PV) properties of the Cu2O/NSTO heterojunction devices. A maximum PV performance is observed in ITO/Cu2O/NSTO device when the deposition temperature, film thickness and Nb doping concentration of NSTO are 550 °C, 76 nm, and 0.7 wt% NSTO, respectively. The optimized PV output corresponds to the open circuit voltage, short-circuit current density, fill factor and photovoltaic conversion efficiency about 0.45 V, 1.1 mA/cm2, 46% and 0.23%，respectively. This work offers an insight into the strategy for developing and designing novel optoelectronics of NSTO-based oxide heterostructures.