Enhanced Electron Transport in Dye-Sensitized Solar Cells Using Short ZnO Nanotips on A Mirco-textured Metal Anode

Abstract

AbstractMuch attention has been directed towards the enhancement of electron transport in dye-sensitized solar cells (DSSC) using one-dimensional nanoarchitectured semiconductors. However, the improvement resulting from these ordered 1-D nanostructured electrodes is often offset or diminished by the deterioration in other device parameters intrinsically associated with the use of these 1-D nanostrucutres, such as the two-sided effects of the length of the nanowires impacting the series resistance and roughness factor. In this work, we mitigate this problem by allocating part of the roughness factor to the collecting anode instead of imparting all the roughness factors onto the semiconductor layer. A microscopically rough Zn microtip array is used as an anode on which ZnO nanotips are grown to serve as the semiconductor component in a DSSC. For the same surface roughness factor, our Zn microtip/ZnO nanotip DSSC exhibits an enhanced fill factor compared to a corresponding planar anode supported ZnO nanowire DSSC. In addition, the open circuit voltage of the Zn-microtip|ZnO-nanotip DSSC is also enhanced due to a favorable band shift at the Zn-ZnO interface, which raises the quasi Fermi level of the semiconductor and consequently enlarges the energy gap between the quasi Fermi level of ZnO and the redox species. The overall improvement demonstrates a new fundamental approach to enhance the efficiency of dye-sensitized solar cells.