Control of Photocurrent Generation in Polymer/ZnO Nanorod Solar Cells by Using a Solution-Processed TiO₂ Overlayer

We report herein the fabrication of hybrid conjugated polymer/ZnO photovoltaic devices using ZnO nanorod structures prepared by electrodeposition and study the effect of introducing a second metal oxide overlayer using a TiCl₄ post-treatment. We use transient absorption spectroscopy, scanning electron microscopy, and photovoltaic device measurements to study the microstructure and charge generation properties of the hybrid films and the performance of the resulting devices. We show how the ZnO nanostructure can be controlled via the nanorod growth conditions and demonstrate that photovoltaic device performance can be optimized by controlling the nanostructure in this way. Moreover, we show that a large increase in photocurrent generation can be achieved by coating the ZnO surface with a thin layer of titanium oxide by treating the ZnO nanostructure with a TiCl₄ solution