Efficiency enhancement in dye-sensitized solar cells irrespective of the electrolyte medium by nanostructured tri-layer TiO2 photoanode

Abstract

A nanostructured, tri-layer TiO2 photoanode consisting of a rice grain–shaped (RG), electrospun TiO2 sandwiched between two TiO2 nanoparticle (NP) layers has been successfully used for the efficiency enhancement in dye-sensitized solar cells (DSSCs) with three different types of electrolytes. The three different types of electrolytes, liquid, gel, and solid, were prepared, and their solar cell performances were assessed in order to establish that the efficiency enhancement due to the tri-layer TiO2 photoanode occurs irrespective of the electrolyte type. The solar cell parameters of DSSCs with this novel photoanode were compared with DSSCs fabricated using a conventional TiO2 nanoparticle (NP) single-layer photoanode. The electrolytes used were (a) commercially available Solaronix Iodolyte Z-50 liquid electrolyte (LE); (b) gel electrolyte (GE) consisting of PEO, EC, PC, KI, Pr4NI, and I2; and (c) solid electrolyte (SE) consisting of PAN, EC, PC, LiI, Pr4NI, BMII, and I2.. Substantial improvement of efficiency of solar cells with NP/RG/NP composite electrode could be obtained irrespective of the type of the electrolyte medium. For the cells with gel polymer electrolyte (GE) and the solid polymer electrolyte (SE), the efficiency enhancement is 26.9% and 21.5% respectively, while the efficiency enhancement for the liquid electrolyte–based cell is 19.4%. The short-circuit photocurrent density values showed a similar enhancement due to the composite TiO2 photoanode. These findings suggest that the efficiency and the photocurrent are enhanced considerably by the tri-layered photoanode structure evidently due to the improved light absorption by scattering events in the TiO2 tri-layer.