Design and Synthesis of Novel NIR Sensitive Unsymmetrical Squaraine Dyes for Molecular Photovoltaics

Two novel NIR-sensitive unsymmetrical squaraine dyes, SQ-258 and SQ-259, for their suitability as a sensitizer in dye-sensitized solar cells (DSSCs) were designed synthesized, followed by photophysical photovoltaic characterizations. It was demonstrated that introducing 1,3-indandione acceptor unit the central squaric acid core of SQ-259 led to suppression dye aggregation owing its non-planar molecular geometry broadening optical absorption photon harvesting window up 800 nm. Owing extended wavelength harvesting, improved photoconversion efficiency (PCE) compared counterpart. However, despite wide improvement PCE less pronounced, this has been attributed small driving force injection electrons (0.29 eV), hampered electronic coupling, decreased lifetime resistance recombination (7.9 ms), which confirmed cyclic voltammetry, quantum chemical calculation, electrochemical impedance spectroscopic investigations, respectively. This article is protected copyright. All rights reserved.