Highly flexible TiO2/C nanofibrous film for flexible dye-sensitized solar cells as a platinum- and transparent conducting oxide-free flexible counter electrode

In this study, highly flexible TiO2/C nanofibrous film was fabricated via electrospinning followed by thermostabilization and carbonizaiton. These nanofibers (NFs) composed of carbon and TiO2 nanoparticles (NPs) with incorporation of TiO2 NPs into carbon matrix. The content of polyvinylpyrrolidone (PVP) and titanium (IV) isopropoxide (TiP) were adjusted to optimize the performance of the TiO2/C nanofibrous film. The results show that the average diameter of TiO2/C NFs and the content of carbon in NFs decreased as the proportion of PVP increased. With addition of PVP, TiO2 NPs distributed more uniformly. With increase of TiP, the average diameter and content of TiO2 increased. As a result, the conductivity decreased with the increase of PVP and TiP. While, the flexibility increased, reaching a best value before decreasing as the PVP and TiP increased. The TiO2/C nanofibrous film presented best flexibility with the content of PVP and TiP of 50% and 0.7 g. Notably, the flexible TiO2/C nanofibrous film showed pleasurable catalytic activity. Therefore, the TiO2/C nanofibrous film served as platinum (Pt)- and transparent conducting oxide (TCO)-free counter electrode (CE) for flexible dye-sensitized solar cells (FDSSCs). Besides, the TiO2/C nanofibrous film CE withstood large deformation of bending and exhibited excellent bending stability.