Significantly Enhancing the Efficiency of a New Light-Harvesting Polymer with Alkylthio naphthyl Substituents Compared to Their Alkoxyl Analogs

摘要

In this work, a new benzo[1,2-b:4,5-b']dithiophene (BDT) building block containing alkylthio naphthyl as a side chain is designed and synthesized, and the resulting polymer, namely PBDTNS-BDD, shows a lower HOMO energy level than that of its alkoxyl naphthyl counterpart PBDTNO-BDD. An optimized photovoltaic device using PBDTNS-BDD as a donor exhibits power conversion efficiencies (PCE) of 8.70% and 9.28% with the fullerene derivative PC71BM and the fullerene-free small molecule ITIC as acceptors, respectively. Surprisingly, ternary blend devices based on PBDTNS-BDD and two acceptors, namely PC71BM and ITIC, shows a PCE of 11.21%, which is much higher than that of PBDTNO-BDD based ternary devices (7.85%) even under optimized conditions.