Photoelectrochemistry at SnO2 particulate fractal electrodes sensitized by a ruthenium complex: Solid-state solar cell assembling by incorporating a composite polymer electrolyte

Nanocrystalline tin oxide thin film electrodes were prepared and their structural and morphological properties were characterized. X-ray diffraction (XRD) confirmed the films crystallinity, whereas both scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed the presence of a porous and fractal network of interconnected nanoparticles forming uniform surface features of relatively low roughness. The SnO2 particulate fractal electrodes were successfully sensitized by the ruthenium N3 complex and solid-state solar cells were assembled by incorporating a binary polymer/inorganic oxide electrolyte. The incorporation of the composite electrolyte consisting of poly(ethylene) oxide (PEO) filled with titanium oxide and containing LiI and I2 as the redox couple presents a satisfying cell performance in comparison with a liquid junction photoelectrochemical cell: typical maximum incident photon to current efficiency (IPCE) as high as 46% at 510 nm, short-circuit photocurrent (Jsc) of 2.6 mA cm−2 and overall conversion efficiency (η) of 0.14% under white light illumination were obtained. The IPCE values of the solid-state dye-sensitised solar cells based on SnO2 are high enough and can be compared to those obtained with titania nanoporous electrodes. The relatively low light to power energy conversion efficiency is attributed to the poor fill factor (FF=0.21) and photovoltage (Voc=0.21 V), characteristics that are related to the reduction of triodide by conduction band electrons and the intrinsic properties of tin oxide.