Nanostructured WO₃ layer as an interfacial modifier for transparent electrodes: enhancing wettability and optical properties for OPVs

Abstract This study investigates the influence of nanostructured tungsten trioxide (WO 3 ) films on the surface properties of transparent electrodes used in organic photovoltaics, specifically indium tin oxide (ITO) and fluorine-doped tin oxide (FTO). The aim is to improve their compatibility with the conductive polymer PEDOT: PSS used as a hole-transport layer (HTL). We show that pulsed laser deposition (PLD) parameters, particularly the number of laser pulses, influence surface architecture, wettability, and optical behaviour of WO₃. The X-ray diffraction investigation reveals that thicker layers adopt a monoclinic structure. The integration of PEDOT: PSS with nanostructured WO₃ layers could help mitigate degradation caused by PEDOT: PSS acidity, creating interfacial conditions that have been associated in the literature with improved device stability and performance. Optical measurements show that thicker WO₃ films enhance absorption in the ultraviolet and near-infrared regions while maintaining high transmittance in the visible range. Additionally, the surface morphology of the WO₃ layer significantly improves electrode hydrophilicity, reducing the water contact angle and enabling uniform PEDOT: PSS deposition without changing HTL thickness. The nanostructured WO₃ film acts as an interfacial modifier that preserves HTL thickness, an important parameter for organic photovoltaic cells and other optoelectronic devices, requiring stable interfaces and efficient charge transport. These insights contribute to the optimization of transparent electrodes for enhanced efficiency in organic photovoltaic applications.