Co-grafting of surfactants: a facile and effective method for the performance enhancement of plastic crystal based solid-state dye-sensitized solar cells

Abstract

The charge recombination at the TiO₂ photoelectrode/electrolyte interface plays a crucial role in determining the efficiency of solid-state dye-sensitized solar cells (DSSCs) because of the poor interface contact at the TiO₂ photoelectrode/electrolyte interface. In this work, we report the surface co-grafting of surfactants onto the surface of the TiO₂ photoelectrode, and their effects on the photovoltaic performance of solid-state DSSCs. Three ionic surfactants, including anionic surfactants, sodium 2-ethylhexyl sulfosuccinate (AOT) and chenodeoxycholic acid (CDCA), and a cationic surfactant, dodecyltrimethylammonium bromide (DTAB), were applied for the modification of the TiO₂ photoelectrode/electrolyte interface. The results show that co-grafting of surfactants AOT or CDCA on the TiO₂ photoelectrode surface, and post heat treatment (above the melting point of solid-state electrolytes) could drastically improve the interfacial contact properties of the TiO₂ photoelectrode/electrolyte interface, increase the penetration of the electrolytes into the porous TiO₂ photoelectrode, and thus enhance the photovoltaic performances of the solid-state electrolyte DSSCs. With the surface modification of AOT/N719, the succinonitrile based solid-state DSSCs exhibited superior long-term stability, and showed power conversion efficiencies of 6.75% and 7.92% under 1.5 solar spectrum illuminations at 100 and 50 mW cm⁻², respectively.