High-efficiency ternary nonfullerene polymer solar cells with increased phase purity and reduced nonradiative energy loss†
In this work, we used a ternary blend strategy to improve the photovoltaic performance of organic solar cells (OSCs). PBDB-T:IDT-EDOT-based binary blend devices show a power conversion efficiency (PCE) of 9.93%, and the ternary devices with PC71BM as the third component exhibit a PCE of 12.07% with simultaneously enhanced Voc, Jsc and FF. The broadened absorption, optimized morphology and balanced charge carrier mobility of these devices are responsible for these improvements. The introduction of PC71BM can disperse the IDT-EDOT aggregates, enhance the phase purity, and increase the electroluminescence quantum efficiency (EQEEL). Furthermore, the performance of the ternary devices is not very sensitive to the weight ratio of the two acceptors. PCEs of over 11% are obtained even though the composition gradually varies from 1 : 1 : 0.2 to 1 : 0.4 : 0.8. Our results demonstrate that PC71BM is a highly promising second acceptor for the construction of high-efficiency ternary OSCs.