Ruthenium(ii) containing supramolecular polymers with cyclopentadithiophene–benzothiazole conjugated bridges for photovoltaic applications

Abstract

Two novel supramolecular polymers (PHBTRU and PFBTRU) containing ruthenium(II) metal ions and bis-terpyridyl ligands with cyclopentadithiophene–benzothiazole conjugated bridges, have been successfully synthesized for application in polymer solar cells by the supramolecular self-assembly process. Both polymers exhibit appropriate solubility in organic solvents and excellent thermal stability with decomposition temperatures over 400 °C. The UV-vis and cyclic voltammetry results show that the resulting polymers have good light-harvesting abilities, low bandgaps as well as low-lying HOMO levels. Compared to polymer PHBTRU, the fluorine atom effect significantly improves the above optical and electrochemical properties of PFBTRU. The photovoltaic devices based on PHBTRU and PFBTRU were fabricated and evaluated with a conventional structure of ITO/PEDOT:PSS/polymer:PC₇₁BM/Ca/Al. The PFBTRU device exhibited the highest power conversion efficiency (PCE) of 2.66% with a V_oc of 0.73 V, a J_sc of 7.12 mA cm⁻² and a FF of 0.51, which was obtained without any additives and/or posttreatment of the active films. The photovoltaic performance achieved in this work is the best result of the reported supramolecular polymers being used in conventional BHJ polymer solar cells.