D–π–A Dyes with an Intramolecular B–N Coordination Bond as a Key Scaffold for Electronic Structural Tuning and Their Application in Dye-Sensitized Solar Cells

Abstract

Abstract A series of D–π–A dyes (AK1–5) was designed and synthesized for applications in dye-sensitized solar cells (DSSCs). AK1–5 contain triphenylamines as electron donors (D), bithiophene π-spacers, boryl-substituted thienylthiazole as electron acceptors (A), and carboxylic acid derivatives as anchor groups. Electrochemical and photophysical measurements on AK1–5 revealed that the use of boryl-substituted thienylthiazole moieties with intramolecular B–N coordination bonds effectively increases the electron-accepting ability of such dyes. The electronic effects of the substituents on the boron center, as well as those of the anchor group enable fine-tuning of the LUMO level, which leads to red shift of the absorption bands of these dyes. Subsequently, DSSCs based on AK1–5 were fabricated, and their performance was examined in terms of the relationship between their electronic structure and the absorption range for photon-to-electricity conversion.