The benefits of utilizing nanowire-based photoanodes for dye sensitized solar cells is quickly becoming apparent. Nanowire structures allow for the presence of an interfacial electric field that is otherwise absent in nanoparticle-based dye sensitized solar cells (DSSCs). This electric field enhances charge transport by inducing potential gradient migration. This mechanism does not occur in nanoparticle-based devices, which are limited to charge transport by only diffusion. Additionally, the presence of an interfacial electric field is believed to reduce the rate of photogenerated electron back reaction with the electrolyte, enhancing photocurrent and allowing for differing electrolyte compositions that may increase photovoltage. Furthermore, the use of conductive core/semiconductive shell nanowire structures decouples the length a photogenerated charge must travel to be collected from the photoanode thickness (and thus overall photoactive surface area).
In this computational study, we investigate how the presence of an interfacial electric field affects interfacial charge transfer, bulk charge transport and charge carrier distributions. The numerical results indicate that electron loss reactions are 1000-fold less when an interfacial electric field is present. Furthermore, varying the special parameters of the photoanode to optimize performance indicates that DSSCs with photoanodes much thicker than 10 Ám (the optimal thickness for nanoparticle-based DSSCs) can be used. This result indicates that efficiencies much larger than the current 12% achievement are attainable through conductive core/semiconductive shell nanowire arrays.