Highly Efficient Non-Fullerene Polymer Solar Cells from Benzo[1,2-b:4,5-b’]difuran-Based Conjugated Polymer with Improved Stabilities
In this work, a novel benzo[1,2-b:4,5-b′]difuran (BDF)-based polymer (PDiFPBDF-TBz, F13) was designed and synthesized with a wide bandgap of 1.90eV. With advantage of electronegative fluorine and furan units, F13 possessed a deep HOMO level of -5.54eV, which is favorable for higher Voc in polymer solar cell (PSC). When F13 was blended with Y6, the device obtained a PCE of 12.7% with a Voc of 0.80V, a Jsc of 22.61 mA/cm2 and an FF of 70.28%. More surprisingly, the un-encapsulated pristine fabricated device will generate a higher PCE of up to 13.34% after storing under nitrogen or air. Further studies showed that the un-encapsulated devices could remain ~92% of its original PCEs even exposure to air in ~1150 hours and nitrogen in ~1370 hours, indicating very promising stabilities. This improvement was from the interfacial interaction of active layer and anode layer and the stable micromophological structure of F13:Y6 film. F13:Y6 device also exhibited a suppressed energy loss of 0.525eV, which is among the smallest one in BDF polymers-based NF-PSCs. These results demonstrate that the rational design of BDF polymer is highly critical in reaching the state-of-the-art photovoltaic performance and the long-term stability.