Effect of the molecular weight of poly(3-hexylthiophene) on the performance of solid-state dye-sensitized solar cells

Abstract

Conductive polymers have become one of the most promising alternatives to liquid electrolytes in dye-sensitized solar cells (DSCs) in order to avoid solvent evaporation and leakage problems. Herein the performance of solid-state DSCs based on poly(3-hexylthiophene) (P3HT) of different molecular weights (MWs) as a hole transport material has been investigated. The DSC devices using the heteroleptic Ru complex Z907Na as a sensitizer in combination with P3HT of MW 30 kDa reach power conversion efficiencies of 1.0%. The mechanism of the photocurrent generation and the role of P3HT in the solid-state DSC devices has been discussed, showing that there is a non-uniform filtration of P3HT with a high MW into the TiO₂ mesoporous film, and thus resulting in an acceleration of the charge recombination close to the TiO₂/Z907Na/P3HT heterojunction interface.