Oxygen vacancies induced enhancement of photoconductivity of La_0.5Sr_0.5CoO_3-δ thin film

Effects of light and electrical current on the electrical transport properties and photovoltaic properties of oxygen-stoichiometric La_0.5Sr_0.5CoO₃ and oxygendeficient La_0.5Sr_0.5CoO_3-δ films prepared by pulsed laser deposition have been investigated. Oxygen-deficient films annealed in a vacuum show an obvious increase of resistance and lattice parameter. Besides, a direct correlation between the magnitude of the photoconductivity and oxygen vacancies in La_0.5Sr_0.5CoO_3-δ films has been observed. The light illumination causes a resistance drop to show the photoconductivity effect. Moreover, the photoconductivity can be remarkably enhanced by increasing the electrical current, that is, it exhibits current-enhanced photoconductivity (CEPC) effect. Oxygen deficiency in the annealed film leads to the formation of a structural disorder in the Co-O-Co conduction channel due to the accumulated oxygen vacancies and hence is believed to be responsible for the increase in higher photoconductivity. These results may be important for practical applications in photoelectric devices.