Metal-free Organic Dyes Featuring an Azobenzene Bridge for Photochromic Dye-Sensitized Solar Cells

Abstract

We report the facile synthesis of photochromic donor-pi-acceptor (D-pi-A) dyes featuring an azobenzene spacer with diphenylamine and dimethylamine as donor residues (DPAC and DMAC). We also investigate the spectroscopic and electrochemical properties of these dyes and their application to dye-sensitized solar cells (DSSCs). The trans-cis isomerization of the azobenzene bridge permits regulation of the photovoltaic behaviour in the DSSCs containing iodine- and cobalt-based redox electrolytes. The iodidie/triiodidie redox shuttle is suitable for DMAC-DSSCs, whereas the cobalt redox mediator is optimal for DPAC-DSSCs. DMAC- and DPAC-DSSCs yield power conversion efficiencies (PCEs) up to 1.99 % and 1.08 % under one sun illumination, when the solar cells are at the photostationary (PS) state.