The development of flexible photovoltaic technologies has attracted significant attention due to their potential applications in wearable electronics, portable devices, and building-integrated energy systems. Among third-generation solar technologies, dye-sensitized solar cells (DSSCs) are particularly promising because of their low fabrication cost, ease of processing, and satisfactory performance under various illumination conditions. However, conventional DSSCs generally rely on rigid fluorine-doped tin oxide (FTO) glass substrates and high-temperature sintering processes (450 to 500 °C), limiting their flexibility and compatibility with roll-to-roll manufacturing. The use of polymeric substrates offers an attractive alternative, but their low thermal stability requires the development of new low-temperature photoanode fabrication strategies. In this work, a novel low-temperature approach was proposed to fabricate flexible PET/TiO₂ composite nanofibrous photoanodes for DSSC applications.

The main objective of this study was to investigate the influence of TiO₂ nanoparticle distribution within electrospun polyethylene terephthalate (PET) nanofibers on the photovoltaic performance of flexible DSSCs. To achieve this objective, highly porous PET/TiO₂ nanocomposite mats were fabricated using three different techniques: uniaxial electrospinning (UE), coaxial electrospinning (CE), and electrospinning coupled with electrospraying (E-ES). These methods enabled precise control over the localization of TiO₂ nanobars either within the fiber bulk, in the shell layer, or directly on the nanofiber surface. The originality of this work lies in the use of surfactant-capped one-dimensional TiO₂ nanobars and in the development of flexible photoanodes in which TiO₂ nanoparticles are strategically positioned at the fiber surface without requiring any post-sintering treatment. To the best of our knowledge, this is the first report describing the use of electrospun PET/TiO₂ nanofibrous structures incorporating TiO₂ nanobars as flexible photoanodes in DSSCs.

Morphological characterization by scanning electron microscopy revealed that both UE and CE methods produced homogeneous porous nanofibrous structures, whereas the E-ES process generated PET fibers decorated with TiO₂ aggregates distributed on the fiber surface and within the porous network. This architecture significantly increased surface roughness and the availability of TiO₂ active sites. Dye adsorption experiments using N719 dye demonstrated that the E-ES photoanodes exhibited superior dye-loading capacity, with increases of 110% and 337% compared with CE and UE photoanodes, respectively. The enhanced dye adsorption was attributed to the greater exposure of TiO₂ nanoparticles on the nanofiber surface, facilitating stronger interactions between the semiconductor and dye molecules.

Photovoltaic characterization showed that the position of TiO₂ nanoparticles strongly influences DSSC performance. The DSSCs fabricated with E-ES photoanodes achieved the highest short-circuit current density (0.12 mA cm⁻²), representing a 200% increase compared with the CE-based devices. Electrochemical impedance spectroscopy further confirmed that E-ES photoanodes exhibited lower charge-transfer resistance and reduced electron recombination, thereby enhancing charge collection efficiency.

Overall, this study demonstrates that controlling the spatial distribution of TiO₂ nanoparticles within electrospun PET nanofibers is crucial for improving the performance of flexible DSSCs. The electrospinning-electrospraying (E-ES) strategy provides a simple, low-cost, and scalable route for manufacturing flexible polymer-based photoanodes and represents a promising platform for future lightweight photovoltaic devices.