Synergistic effects of the aspect ratio of TiO2 nanowires and multi-walled carbon nanotube embedment for enhancing photovoltaic performance of dye-sensitized solar cells

The existence of numerous interfacial boundaries among TiO2 nanoparticles (NPs) accumulated in the photoelectrode layer of dye-sensitized solar cells (DSSCs) hinders the effective transport of photogenerated electrons to an electrode. Therefore, as a replacement for TiO2 NPs, one-dimensional TiO2 nanowires (NWs) can be suggested to provide pathways for fast electron transport by significantly reducing the number of interfacial boundaries. In order to provide direct evidence for the better performance of such longer TiO2 NWs than shorter TiO2 NWs, we examine the effect of the controlled aspect ratio of the TiO2 NWs randomly accumulated in the photoelectrode layer on the photovoltaic performance of DSSCs. It is clearly found that longer TiO2 NWs significantly improve the electron transport by reducing the TiO2/dye/electrolyte interfacial contact resistance. Furthermore, the embedment of multi-walled carbon nanotubes (MWCNTs) as an effective charge transfer medium in longer TiO2 NWs is proposed in this study to promote more synergistic effects, which lead to significant improvements in the photovoltaic properties of DSSCs.