Low-temperature (70 °C) ambient air plasma-fabrication of inkjet-printed mesoporous TiO ₂ flexible photoanodes

Abstract Titania/silica electron-generating and -transporting nanocomposite 300 nm layers of high porosity were deposited onto ITO/PET flexible foils using inkjet printing. Prior to printing, the ITO surface had been modified by novel low-temperature ambient air roll-to-roll plasma in order to enhance its surface properties by removing carbon and oxygen contaminants, a process that led to rapid improvement of surface energy. Consequently the ITO work function, an important parameter involving charge injection efficiency in energy harvesting systems, increased by 1 eV. Afterwards, the TiO ₂ /methyl-silica ink exhibited excellent wetting on a 2 s plasma-treated ITO surface. The coating was further processed/mineralized by an additional low-temperature ambient air plasma treatment step. The plasma processing of raw photoanodes led to the mineralization of the methyl-silica binder which resulted in the formation of a fully inorganic TiO ₂ /SiO ₂ mesoporous structure and significantly increased electrophotocatalytic activity, leading to increased photocurrents. The entire two-step plasma process was performed at low-temperature (70 °C) and high speeds, enabling practical applications of such a procedure for large-area fabrication of flexible photoanodes.