We constructed an effective electron extraction layer (EEL) used for polymer solar cells by integrating one new kind of organic material of 4,4′-(1,4-phenylene) bis(2-phenyl-6-p-tolylnicotinonitrile) (p-PPtNT) and cesium carbonate (Cs₂CO₃) used as a compound EEL (CEEL). The CEEL based device exhibits an ideal PCE of 4.15%, corresponding to an enhancement 220% in contrast to that of control device without EEL, which is also comparable to that of ZnO based device. Our analyses indicated that the remarkably improved PCE for CEEL based device is mainly ascribed to the Ohmic contact and the negligible electron extraction barrier at cathode/active layer by inserting CEEL. 

Optics Communications, 2015 

AFM images of (a) ITO/ZnO, (b) ITO/ZnO/P3HT:PCBM, (c) ITO/ Cs₂CO₃(0.6 nm)/p-PPtNT (20 nm), and (d) ITO/Cs₂CO₃ (0.6 nm)/p-PPtNT (20 nm) /P3HT:PCBM.