Medium band gap conjugated polymers from thienoacene derivatives and pentacyclic aromatic lactam as promising alternatives of poly(3-hexylthiophene) in photovoltaic application

Two alternating medium band gap conjugated polymers (PBDT-TPTI and PDTBDT-TPTI) derived from 4,8-bis(4,5-dioctylthien-2-yl)benzo[1,2-b:4,5-b]dithiophene (BDT-T) or 5,10-bis(4,5-didecylthien-2-yl)dithieno[2,3-d:2,3-d]benzo[1,2-b:4,5-b]dithiophene (DTBDT-T) with pentacyclic aromatic lactam of N,N-didodecylthieno[2,3:5,6]pyrido[3,4-g]thieno[3,2-c]-iso-quinoline-5,11-dione (TPTI), are synthesized and characterized. The comparative investigation of the photostabilities of the copolymers revealed that the PDTBDT-TPTI film exhibited the comparable photostability in relative to P3HT. Meanwhile, the inverted photovoltaic cells (i-PVCs) from the blend films of PBDT-TPTI and/or PDTBDT-TPTI with PC71BM, in which poly[(9,9-bis(3-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)] were used as cathode modifying interlayer, presented higher power conversion efficiencies (PCEs) of 5.98% and 6.05% with photocurrent response ranging from 300 nm to 650 nm in contrast with the PCEs of 4.48% for the optimal inverted PVCs from P3HT/PC71BM under AM 1.5 G 100 mW/cm(2). The PCEs of the i-PVCs from PBDT-TPTI and PDTBDT-TPTI were improved to 7.58% and 6.91% in contrast to that of 0.02% for the P3HT-based i-PVCs, and the photocurrent responses of the devices were extended to 300-792 nm, when the ITIC was used as electron acceptor materials. The results indicate that the PBDT-TPTI and PDTBDT-TPTI can be used as the promising alternatives of notable P3HT in the photovoltaic application. (c) 2017 Wiley Periodicals, Inc.