Phenothiazine-based dyes with bilateral extension of π-conjugation for efficient dye-sensitized solar cells

Four novel organic photo-sensitizers based on phenothiazine were designed, synthesized and characterized for efficient dye-sensitized solar cells. Anisole, octyloxybenzene and dodecyloxybenzene were incorporated into the phenothiazine by an Ullmann reaction. An additional octyloxybenzene was incorporated into one dye unit through a Suzuki coupling reaction. The modified phenothiazine moiety acts as an electron donor and cyanoacrylic acid acts as an electron acceptor and anchoring unit. The photophysical, electrochemical and sensitizing characteristics of the new dyes were evaluated. The bis(octyloxybenzene) substituted dye delivered the best performance with its sensitized solar cell displaying an overall power conversion efficiency of 5.73% under standard illumination. The results indicate that bilateral conjugate extension of the pi conjugation can increase their light harvesting capacity and electron lifetime, leading to improvements in the efficiency of their dye-sensitized solar cells. (C) 2012 Elsevier Ltd. All rights reserved.