Enhancement of persistent photoconductivity of ZnO nanorods under polyvinyl alcohol encapsulation

We report on the observation of enhanced and persistent ultraviolet (UV) photoconductivity of polyvinyl alcohol (PVA) encapsulated ZnO nanorods. A simple aqueous solution growth technique is adopted to grow ZnO nanorods in the form of thin film as well as powder. The morphological features of nanorods (before and after PVA coating) have been studied using electron microscopy. Both bare and PVA coated nanorods are found to exhibit photoconductivity under UV light illumination. PVA encapsulation of nanorods has led to the lower adsorption of oxygen molecules on the surface of nanorods leading to the exhibition of high dark current and a slower growth in photocurrent under steady illumination. The appealing aspect of the present investigation lies in the observation of highly enhanced persistent photoconductivity in the encapsulated nanorods. Based on the fact of confinement of the desorbed oxygen molecules, a new mechanism has been proposed to support the encapsulation led enhancement in persistent photoconductivity. The encapsulation led confinement of the desorbed oxygen molecules around the nanorods results in the faster development of surface built-in potential and hence exhibits enhanced persistent photoconductivity, thereby indicating the uniqueness of the proposed mechanism.