Interfacial engineering of pulsed laser synthesized ternary TiO₂/rGO/WS₂ semiconductor photoanodes for efficient charge transport in dye-sensitized solar cells

This study focuses on interfacial engineering of semiconductor photoanodes to enhance charge transport in dye-sensitized solar cells (DSSCs) by fabricating binary (TiO₂/rGO) and ternary (TiO₂/rGO/WS₂) semiconductor nanocomposites via pulsed laser ablation in liquid (PLAL). The PLAL technique involves irradiating a high-energy pulsed laser in a liquid environment, generating plasma and cavitation bubbles whose rapid collapse produces strong shockwaves, yielding highly pure binary TiO₂/rGO and ternary TiO₂/rGO/WS₂ semiconductor nanocomposites. The synthesized nanomaterials were systematically characterized using XRD, XPS, SEM, TEM, UV-vis spectroscopy, and PL measurements. The Kubelka-Munk function was used to calculate band gap energies from diffuse reflectance spectroscopy (DRS), which were found to be 3.27 eV for pristine TiO₂, 3.24 eV for binary TiO₂/rGO, and 2.97 eV for the ternary system, indicating enhanced visible-light absorption in the ternary system. Furthermore, DFT calculations were employed to elucidate the interfacial electronic interaction and charge redistribution within the ternary TiO₂/rGO/WS₂ nanocomposite, revealing favourable density-of-states alignment for charge transfer. We found that DSSC fabricated with a ternary TiO₂/rGO/WS₂ photoanode showed a high J_SC of 18.16 mA/cm², FF of 59.58%, and V_OC of 0.68 V, resulting in improved power conversion efficiency (PCE) of 7.36% compared to the binary (PCE of 6.40%) and pristine TiO₂ (PCE of 5.18%) photoanode devices. The enhanced performance is attributed to a rGO mediated conductive network and WS₂ driven interfacial charge separation, leading to suppressed recombination losses and improved charge collection efficiency in ternary TiO₂/rGO/WS₂ semiconductor photoanode-based DSSCs.