Improving energy harvesting efficiency of dye sensitized solar cell by using cobalt-rGO co-doped TiO₂ photoanode

In dye-sensitized solar cells (DSSCs), TiO₂ has long been a popular electron transport material for carrying photo-generated electrons from the dye to the outer circuit. However, increasing the electrical conductivity of TiO₂ while preserving its properties is one of the most significant challenges for increasing DSSC efficiency. Here, cobalt-reduced graphene oxide co-doped TiO₂ nanoparticles were synthesized by a modified sol-gel procfess that together controlled the particle size as well as narrowed bandgap of nanoparticles as determined by XRD and UV-Vis absorption measurements. The SEM and TEM were used to perform in-depth morphological characterization of the newly synthesized nanocomposites while J-V (current-voltage) curves, EIS Nyquist curves, and incident photon to current conversion efficiency (IPCE) spectra were used to examine the photovoltaic parameters. Enhanced short circuit current density (J_sc 12.83 mA cm⁻²), open-circuit voltage (V_oc 0.618 V) and overall power conversion efficiency (PCE, η = 5.24%) of DSSC was obtained with Co/rGO co-doped TiO₂ based photoanode in comparison to bare TiO₂ (η = 3.71%), cobalt doped TiO₂ (η = 4.09%) and rGO doped TiO₂ (η = 4.43%) based DSSCs. Huge improvement in efficiency, 41% higher PEC in Co/rGO co-doped TiO₂, was attributed to better utilization of visible radiations, greater dye adsorption and enhancement in charge transfer properties by suppressing the electron transport resistances. The incorporation of rGO improved electron transfer, which compensated for recombination losses, thereby increasing the DSSC's J_sc. The synergetic role of rGO and transition metal helped in keeping the structure intact in the nano-assembly that enhance the photo-generated carriers.