Facile synthesized benzo[1,2-b:4,5-b']difuran based copolymer for both fullerene and non-fullerene organic solar cells

Abstract

A novel D-A conjugated polymer, PFBT-T, consisting of alkyl substituted benzo[1,2-b:4,5-b']difuran (BDF) as electron donor, alkyl substituted benzo[1,2-c:4,5-c']dithiophene-4,8-dione (BDD) as electron acceptor and thiophene as the π-bridge has been designed and synthesized through facile Stille coupling reaction. Compared with its reported similar polymer based on benzo[1,2-b:4,5-b']thiophene (BDT) unit, PFBT-T has deeper LUMO and HOMO energy level and more intense absorption in 350–550 nm, leading to higher short-circuit current density (Jsc) and open circuit voltages (Voc). Organic solar cells (OSCs) based on PFBT-T with architecture of ITO/PEDOT:PSS/PFBT-T:(PC71BM or IT-M)/PDINO/Al were fabricated. OSCs using PC71BM or IT-M as acceptors respectively obtained the power conversion efficiencies (PCEs) of 5.83% and 5.64%, which both were better than OSCs based on its BDT-based analogues. These results demonstrated that BDF was a promising donor constructing block which may replace BDT unit in some cases.