Figure 9

Energy level diagrams.
Energy level diagrams of (a) ITO/PEDOT:PSS/PTB7/PC71BM and (b) ITO/PEDOT:PSS/P3HT/PC61BM. Фh and eD are the hole extraction barrier and interface dipole, respectively. ΨITO, ΨPEDOT:PSS, ΨPTB7, ΨPC71BM, ΨP3HT and ΨPC61BM are the work functions of ITO, PEDOT:PSS, PTB7, PC71BM, P3HT and PC61BM, respectively. Comparing the diagrams, we observed the strong interface dipole between P3HT and PC61BM. Schematic image of (c) PC71BM and PTB7 and (d) PC61BM and P3HT interfaces.