Gamma irradiation-induced enhancement of electrochemical activity in plastic waste-derived PET/Al2O3/TiO2 counter electrodes for DSSCs

Harnessing the dual potential of waste valorization and renewable energy innovation, this research explores a transformative approach to solar cell technology. By converting recycled plastic waste into functional nanocomposite materials, the study addresses two global challenges simultaneously: plastic pollution and the demand for clean energy. Herein, a novel counter electrode (CE) framework for dye-sensitized solar cells (DSSCs) is introduced, based on recycled polyethylene terephthalate (PET) reinforced with Al2O3 and TiO2 nanoparticles (NPs), further engineered via controlled γ-irradiation at doses of 0–50 kGy. Systematic characterization revealed that γ-irradiation progressively enhanced surface roughness, porosity, and wettability, with optimal modification at 40 kGy, facilitating better electrolyte infiltration, catalytic site accessibility, and electron transfer kinetics. These structural enhancements facilitated superior electrolyte infiltration and catalytic site accessibility, accompanied by optical band gap narrowing (3.02 → 2.13 eV) and a marked decrease in charge-transfer resistance (Rct: 50 Ω → 12 Ω). These interfacial improvements directly translated into superior photovoltaic output, with power conversion efficiency (PCE) rising from 5.22% (PAT0) to 7.69% at 40 kGy (PAT40), closely approaching the Pt benchmark (8.01%). Notably, PAT40 achieved optimized short-circuit current density (18.54 mA/cm2) and fill factor (68%), underscoring the synergy between structural evolution and catalytic activity induced by controlled γ-irradiation. Beyond performance, this work highlights an eco-conscious strategy by valorizing PET waste into high-value DSSC components, thereby integrating plastic waste reduction with clean energy generation. This work not only validates radiation processing as a powerful tool for tuning polymer–nanoparticle composites but also highlights the potential of sustainable, low-cost alternatives to precious metal CEs in next-generation solar technologies.