Tuning polythiophene/titanium dioxide (PTh/TiO2) hybrid nanocomposite photoanodes for DSSCs: linking composition, morphology, and enhanced efficiency

Dye-sensitized solar cells (DSSCs) have gained significant attention as a promising class of third-generation photovoltaic devices owing to their low cost, ease of fabrication, and tunable optical properties. However, their practical use is still limited by poor electron transport, charge recombination, and low power conversion efficiency. This study tackles the persistent challenge of low efficiency in dye-sensitized solar cells (DSSCs) by introducing a novel polythiophene/titanium dioxide (PTh/TiO2) hybrid nanocomposite photoanode. The photoanode was fabricated using the tape-casting technique, which enabled the deposition of a uniform TiO2 film. This TiO2 photoanode was later sensitized with cis-Bis(isothiocyanato)bis(2,2′-bipyridyl-4,4′-dicarboxylato)ruthenium(II) (N3dye), allowing efficient light absorption and electron transportation. The device performance was further improved by employing a graphene-based counter electrode. The fabricated photoanodes were systematically characterized using SEM, ellipsometry, UV–Vis spectroscopy, and Hall measurements to investigate the link between material properties and photovoltaic performance. By integrating conductive polymer networks with TiO2 nanoparticles, the hybrid photoanode was developed to boost electron transport and light harvesting. The systematic investigation of PTh/TiO2 loadings revealed that the photoanode containing 9 wt% PTh/TiO₂ achieved the highest DSSC efficiency of 0.86%, with an open-circuit voltage (Voc) of 0.56 V, short-circuit current density (Jsc) of 2.53 mA/cm2, and a fill factor of 58.96%. This composition significantly outperformed devices with lower (5%, 7%) and higher (11%) PTh contents, underscoring the pivotal role of optimized nanocomposite architecture in enhancing charge transport and light harvesting. Furthermore, the results highlighted that increasing nanocomposite concentration directly influenced morphology, film thickness, light absorption capacity, and carrier mobility, ultimately shaping device performance.