Fig. 3.
Energy diagram of an inverted OLED device using a-C12A7:e (EIL) and a-ZSO (ETL). The values of the ionization energy (Ip) were determined from the location of the valence band measured by UPS as shown in Figs. S1 and S2. MoOx and NPD, N,N′-di(1-naphthyl)-N,N′-diphenyl- (1,1′-biphenyl)-4,4′-diamine, are used as hole injection layer (HIL) and HTL, respectively, and CBP doped with Ir(ppy)3, tris[2-phenylpyridinato-C2,N]iridium(III), is used as the EML. Note that the stacking order of injection layer and transport layer for electrons is reversed for the hole. This sequence for the electron is designed to use the ohmic contact between a-ZSO and the cathode materials.