Improved Photovoltaic Properties of Fluorene-Thiophene-Based Copolymers by an Electron-Transporting Triazole Unit in the Main Chain

Abstract

An electron-transporting triazole (Tz) unit was introduced into the fluorene-thiophene-based copolymer backbone via a Suzuki coupling reaction. The resulting copolymer, poly[9,9'-dioctyl-fluorene-co-5, 5-(4', 7'-di-2-thienyl-2', 1',3'-benzothiadiazole)-co-(4-(4-butyl-phenyl)-3, 5-diphenyl-4H-1,2,4]triazole)] (PF3TBTz), was soluble in common organic solvents and can be easily used as the active layer in organic photovoltaic cells (OPVs). By the introduction of the triazole unit, the OPV performance was nearly doubled from 0.62% (PF3TB) to 1.25% (PF3TBTz) under the same conditions. The higher performance can be explained by the improved surface morphology, resulting in better charge photogeneration and higher short circuit current (J(sc)) value in PF3TBTz in comparison with PF3TB. The possibility of the use of triazole units in OPV applications are described herein.