Optimized reduced graphene oxide-tio2 nanocomposite with co-sensitization strategy: enhancing dye-sensitized solar cell performance through advanced interfacial engineering and charge transport optimization

Abstract

This study reports a systematic optimization of reduced graphene oxide (rGO) modified TiO2 photoelectrodes for dye-sensitized solar cells (DSCs), addressing a critical limitation in which device efficiencies had remained below 0.15 percent. Through a comprehensive parametric investigation of rGO loading concentration (0.5 to 10 mg/mL), synthesis temperature (200 to 400 degrees Celsius), and a co-sensitization strategy combining the natural dye Delonix regia with the N719 ruthenium complex, substantial performance gains were realised. Electrochemical impedance spectroscopy revealed that an optimal rGO loading of 3 mg/mL reduced the charge transfer resistance at the photoelectrode and electrolyte interface by sixty seven percent relative to bare TiO2 , while incident photon-to-current conversion efficiency measurements demonstrated a broadened spectral response extending to 800 nm with a peak quantum efficiency of seventy eight percent at 530 nm. The optimized cell, combining a 3 mg/mL rGO-TiO2 photoelectrode, one-to-one co-sensitization, and an electrochemically deposited polyaniline counter electrode, exhibited a short-circuit current density of 8.42 mA/cm2 , an open-circuit voltage of 0.71 V, a fill factor of 0.68, and a power conversion efficiency of 4.06 percent under AM 1.5G illumination, a thirty one fold improvement over the prior baseline. Accelerated aging confirmed retention of ninety one percent of the initial efficiency after one thousand hours of continuous illumination. The synergistic interplay of optimized interfacial properties and complementary light absorption establishes a viable route toward cost effective, durable DSCs built on earth abundant materials and partially natural photosensitizers.