Low glass transition temperature hole transport material in enhanced-performance solid-state dye-sensitized solar cell

A new triarylamine-based hole transport materials (HTM) with branched side chain giving low glass transition temperature (T_g) is synthesized and incorporated into a solid state dye sensitized solar cell. This designing of molecular structure of HTM for lowering the T_g along with viscosity and surface tension of the casting solution effectively increases the pore-filling fraction (PFF) as the cell is heated during the fabrication, leading to an 8 fold increasing in cell efficiency over cells without heat treatment. We relate the cell performance improvement not only due to the PFF of TiO₂ by the (HTM), but also because of morphological and thickness changes in the hole transport material (HTM) capping layer.