Morphological evolution of sol-electrophoretic deposited ZnO nanostructures on anodic TiO2 nanotubes for back-side illuminated dye-sensitised solar cells

Abstract

Efficient photoanodes are essential for dye-sensitized solar cells (DSSCs). We report on sol-electrophoretic deposition of ZnO/TiO2 heterojunction structures with enhanced photocurrent-photovoltage performance for back-side illumination DSSCs. An anodic oxidation method was used for the preparation of TiO2 nanotube arrays (TNAs). ZnO nanostructures with different morphologies were successfully deposited on TNAs via sol-electrophoretic process. The results revealed that TNAs decorated with ZnO favors the photovoltaic properties reaching the best photoanode performance in a pH and temperature of 8.5 and 30°C, respectively, under an electrophoretic deposition (EPD) potential of 10 V. This photoanode generates short circuit current (Jsc) and open circuit voltage (Voc) of 3.28 mA/cm2 and 0.79 V, respectively. Consequently, the power conversion efficiency (PCE) acquired 1.525% with a fill factor of 72% for the best ZnO/TiO2 heterojunction enhances the DSSC performance by 107% with respect to similar TNAs due to the surface passivation of electronic states eliminating the recombination rate.