Graphene-Modified Photoelectrode for Efficient and Cost-Effective Dye-Sensitized Solar Cells

Dye-sensitized solar cells (DSSCs) have been attracted as a real class of building-integrated photovoltaic (BIPV) owing to its natural controllable color transparency, working ability in diffuse light, and low-cost fabrication. The low photoconversion efficiency (PCE) is the main obstacle for BIPV market. The bilayered structure based on mesoporous TiO₂ nanoparticles (NPs) along with TiO₂ blocking layer was introduced to obtain high PCE by optimizing the dye adsorption, avoid recombination via direct electrolyte contact, and enhance light-harvesting ability by providing scattering centers. However, the bilayered structure based on mesoporous TiO₂ network offers inferior charge transfer, thus higher recombination and, consequently, low PCE. In our previous studies, we have developed graphene/TiO₂ blocking layer, graphene/TiO₂ transparent layer, and scattering layer and analyzed individually to improve the electron transport and reduce recombination. In the current work, we have demonstrated the integrated optimized photoelectrode-based DSSCs via the above-mentioned previously developed photoelectrode components with Pt and graphene/polyaniline (PANI) cost-effective counter electrode. Optical property analysis and electrochemical impedance spectroscopy (EIS) have shown that graphene-modified optimum components of photoelectrode have effectively improved the electron transport and light-harvesting ability. Electron lifetime, diffusion coefficient, and diffusion length have been increased by ~87%, ~20%, and ~11%, respectively, as compared to control DSSC based on commercial paste. Consequently, 5.94% of PCE was achieved, which is 20% higher than the DSSCs fabricated with commercial pastes. Moreover, DSSCs based on optimized photoelectrode with graphene/PANI counter electrode have shown 4.04% PCE, which is ~70% of the PCE that was achieved with Pt.