Responsivity of In/ZnO nanoparticles/In and In/Ti0.05Zn0.95O nanoparticles/In devices to solar irradiation

The effect of the incorporation of Ti into ZnO nanoparticles on the responsivity of In/ZnO nanoparticles/In devices to solar irradiation is studied. The dependence of the sensitivity to solar irradiation, response time, grain size, luminescence and defects upon the addition of Ti is determined. The time-resolved photocurrent plot indicates that the rise and decay processes become faster when Ti is incorporated into ZnO nanoparticles. The ratio of photocurrent-to-dark current (i.e., photosensitivity) is about one order of magnitude for In/ZnO nanoparticles/In devices. However, the ratio of photocurrent-to-dark current is three-four orders of magnitude for In/TiZnO nanoparticles/In devices. An oxygen vacancy-related band model is proposed to describe the transition processes for free carrier generation. The incorporation of Ti into ZnO nanoparticles leads to the combined effect of a reduction in the grain size and the reduced number of oxygen vacancies, which serves to reduce the dark current and increase the value of photosensitivity.