Optimized Nb‐Doped TiO2/rGO Nanocomposites for Assessment of Photovoltaic Performance With Metal‐Free Dye and Polymer Gel Electrolyte

Abstract This research presents the development of niobium (Nb)‐doped titania (TiO 2 )/reduced graphene oxide (rGO) nanocomposites (NTR NCs) for dye‐sensitized solar cells (DSSCs). The novelty lies in two aspects: introducing Nb (V) ions into TiO 2 /rGO nanocomposites via an in‐situ sol‐gel method with doping concentrations from 1.0 to 3.0 mol %, and fabricating photoanodes using the doctor blade technique, sensitized with a Co 2+ /Co 3+ ‐based PEO‐PEG polymer gel electrolyte‐assisted D‐π‐A carbazole metal‐free (SK3) dye. Detailed investigations into the optoelectrical, structural, and morphological properties were conducted using various spectral and analytical tools. Notably, DSSCs based on Nb‐doped TiO 2 /rGO nanocomposites with 2.0 mol % Nb (NTR‐2) achieved a remarkable solar efficiency (η) of 5.48 % under AM 1.5 solar simulation, significantly outperforming devices based on bare TiO 2 nanoparticles and undoped TiO 2 /rGO NCs by factors of 4.15 and 2.97, respectively. The substantial enhancement in photovoltaic performance is attributed to superior charge transfer properties and higher carrier density, as revealed by electrochemical impedance spectroscopy (EIS) and Mott‐Schottky (M–S) analysis. Nb‐doping results in an energetic surface nature, improved optical absorption, and reduced charge transfer resistance, collectively boosting the overall efficiency of DSSCs. This work underscores the potential of Nb‐doped TiO 2 /rGO NCs as effective photoanode materials in enhancing DSSC performance.