Although charges can be transferred and collected efficientlyat 1 104 cm2 V1 s1 [28], we believe that Jsc and PCEs offullerene-free OSCs can be further improved with higher electronmobility. Meanwhile, NFAs with high electron mobility areexpected to fabricate thickness-insensitive OSCs, which is veryimportant for large-scale production. To develop NFAs with highelectron mobility, the following aspects should be taken intoconsideration: (1) intramolecular/intermolecular interaction; (2)molecular orientation; (3) crystallinity. It is well known thatextending the conjugated surface and improving the effectiveconjugation is a good way to enhance the electron mobility[71]. In addition, more planar and regioregular main backbonewould induce better p-p stacking and higher degree of crystallinity, and finally higher electron mobility [170–172]. As anexample, bay-linked perylene bisimides, i.e., di-PBI presents anelectron transfer mobility of 3.32 105 cm2V1s1; While thePDI units linked with fused spirobicyclopentabithiophene (FSP)showed improved electron mobility of 7.23 105 cm2V1s1due to enhanced conjugation between the two PDI units. Theenhanced electron mobility resulted in better OSC performancewhen they paired with PTB7-Th as the active layers. The OSCdevices based on di-PBI/PTB7-Th and FSP/PTB7-Th blends presented PCEs of 5.90% and 8.89%, respectively [129,173].