Screen-printed counter-electrodes based on biochar derived from wood-corn silage and titanium isopropoxide binder as a more efficient and renewable alternative to Pt-CE for dye-sensitized solar cells

Current research of counter-electrodes (CEs) for dye-sensitized solar cells (DSSCs) focuses mainly on searching for low-cost and mass-production suitable materials as an alternative to standardly used platinum. One of the most studied groups is carbon allotropes, while carbon-enriched materials such as biochar prepared from renewable sources (biomass) show tremendous potential. Structural properties of biochar, electrical conductivity and large specific area predict the possibility of its use as a catalytic material of CE. To ensure printability and efficient contact between the printed catalytic layer and substrate of CE, non-conductive polymer binders, reducing electrical and electrochemical properties of CEs, are standardly used. This work introduces the prep-aration of screen-printed CEs based on titanium isopropoxide (TTIP) binder and biochar microparticles obtained by pyrolysis of wood and corn silage, which were investigated as an alternative to platinum CE. TTIP was examined as a substitute for the polymer binder ethylcellulose (EC) and as the precursor for TiO2 nanoparticle synthesis in biochar/TTIP hybrid CEs. Formation of polymer matrix from TTIP ensured the required rheological properties of biochar/TTIP inks and improved interparticle contact and mechanical stability of screen-printed catalytic layers of CEs. Raman spectroscopy indicated the presence of TiO2 anatase nanoparticles with a size of 5 nm after CEs sintering at 500 degrees C under an argon atmosphere. The sintering process raised catalytic activity and decreased sheet resistance of CEs in the presence of I-3(-)/I- electrolyte, resulting in enhanced photovoltaic parameters of DSSCs. Screen-printed composite CEs consisting of 30 wt% biochar and 20 wt% TTIP reached the best catalytic activity and higher conversion efficiency of DSSCs (6.43 %) than DSSCs with Pt CEs (6.19 %). Based on the results, combining biochar and TTIP offers new possibilities for developing more ecological and low-cost mass-producible materials for CEs.