Gamma-irradiated Chitosan@PVA@TiO2 catalytic counter electrodes for enhanced dye-sensitized solar cell (DSSC) performance

Abstract

Dye-sensitized solar cells (DSSCs) offer an affordable, versatile, and sustainable renewable energy solution, making them a valuable tool in combating climate change. From this standpoint, gamma irradiation treatment provides a viable approach to enhance the performance of low-cost, platinum-free counter-electrodes (CEs) by increasing the number of active sites, thereby improving their catalytic efficiency in DSSCs. To the best of our knowledge, for the first time, innovative Chitosan@polyvinyl alcohol@Titanium dioxide (Chitosan@PVA@TiO₂) (CPT) hybrid films were developed as a catalytic CE substance and were subjected to a range of in-situ gamma irradiation doses (0, 10, 20, 30 and 40 KGy) with the goal to further improving their microstructural and physicochemical qualities. Coupled with a J–V variable evaluation, physical assessments of the microstructure, porosity, morphology, contact angle, optical, and electrochemical impedance spectroscopy (EIS) properties of CEs were carried out. The surface properties of the treated composites improved progressively with increasing gamma doses, reaching optimal levels at 30 KGy (i.e., apparent porosity = 72.5 %, average roughness (Ra) = 5.31 µm) compared to the pristine CE material. Prolonged gamma irradiation enhanced DSSC efficiency, achieving 6.45 % at 10 KGy and 7.14 % at 20 KGy. The high-energy gamma photons facilitated charge carrier movement within the CPT compounds while reducing recombination by creating conditions favorable for charge dissociation. Hence, improved mobility and reduced resistive limitations equate to longer lifespans and more efficient charge transfer within the solar cell. In this regard, the CPT catalytic CE's optimized yield of 8.57 % and short-circuit photocurrent density (J_sc) of 19.1 mA/cm² were achieved after 30 KGy of modification of the surface. Compared to the pristine sample, effectiveness increased by 41.2 %. This enhancement in photovoltaic performance was attributed to the introduction of oxygen-enriched free radicals into the CPT structure, which created continuous channels for rapid electron transfer. Considering all aspects, this work highlights the critical role of gamma-irradiated CPT catalytic CEs in enhancing DSSC performance, offering a new approach to improving the efficiency of these devices.