Synthesis and applications of thieno[3,4-c]pyrrole-4,6-dione based linear to star-burst novel D–A conjugated oligomers for organic photovoltaics

Abstract

A series of well-defined donor–acceptor (D–A) conjugated oligomers incorporating thieno[3,4-c]pyrrole-4,6-dione (TPD) acceptor and two symmetrical thiophene units as donor π-bridge along the axes of triphenyl amine core have been synthesized and explored in bulk heterojunction (BHJ) solar cells. Under illumination with AM 1.5 white light (100 mW/cm2), the performance of BHJ photovoltaic devices with an active layer of an electron-donor oligomeric material (TPATP1, TPATP2 or TPATP3) blended with an electron acceptor {[6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) or [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) at various weight ratios has been investigated. The photovoltaic device containing the donor TPATP1 and the acceptor PC71BM at a 1:3 weight ratio exhibited the best efficiency of 1.87% with an open circuit voltage (Voc) of 0.86 V, short circuit current (Jsc) of 6.59 mA/cm2, and a fill factor (FF) of 33%. These results demonstrate that irrespective of conjugation length, tuning of materials with efficient donor and acceptor materials can enhance the optical, electrochemical and eventually the power conversion efficiency (PCE) values of BHJ solar cells. Furthermore oligomers containing TPD acceptor in different structural form have different unique contribution towards photovoltaic properties.