Multifunctional PVC-based metal oxide/graphene composites for high-performance DSSC counter electrodes

The development of cost-effective and multifunctional counter electrodes (CEs) remains a critical challenge in advancing dye-sensitized solar cells (DSSCs). In this work, we introduce polyvinyl chloride (PVC)-based nanocomposites incorporating ZnO nanoparticles (NPs) and graphene (G) as high-performance CE materials. A dual strategy combining density functional theory (DFT) simulations and experimental validation was employed to establish a rational design framework. Computational screening of diverse metal oxides (MgO, SiO₂, TiO₂, NiO, CuO, ZnO, and ZrO₂) identified ZnO as the most promising candidate due to its favorable dipole moment, band-gap modulation, and charge-transfer characteristics. Subsequent graphene incorporation was predicted to synergistically enhance conductivity and catalytic activity, which was experimentally confirmed. Structural and morphological analyses revealed progressive pore evolution and increased surface roughness with ZnO and graphene loading, directly correlating with improved electrochemical performance. Specifically, PVC/ZnO/G composites exhibited the highest conductivity (66 S/m), enlarged average pore size (2.97 μm), and superior surface roughness (Ra = 8.5 μm), facilitating efficient electrolyte diffusion and rapid charge transport. Electrochemical impedance spectroscopy confirmed accelerated charge transfer with a markedly reduced charge-transfer resistance. J-V characterization further validated superior photovoltaic performance: PVC/ZnO/G achieved a short-circuit current density (J_sc) of 17.894 mA/cm², and a fill factor (FF) of 61.2%, yielding a power conversion efficiency (PCE) of 7.547%, compared to 4.697% for pristine PVC. These enhancements are attributed to the synergistic interplay between ZnO and graphene, which collectively promote efficient electrolyte diffusion, light harvesting, and interfacial charge transport. This study demonstrates, for the first time, the integration of computational screening with experimental validation to develop PVC/ZnO/G as a scalable and cost-effective CE. Beyond offering a viable alternative to Pt-based electrodes, this work establishes a design blueprint for tailoring polymer-metal oxide-graphene hybrids to enable next-generation high-performance and sustainable DSSCs.