(a) Chemical structures of mCP and TPBi. (b) Energy level of nondoped devices with electroplex emission. Device configurations: ITO/MoO3 (10 nm)/NPB (60 nm)/mCP (15 nm)/EML (30 nm)/TPBi (30 nm)/LiF (1 nm)/Al. (c) External quantum efficiency-luminance characteristics of the nondoped devices. (d) EL spectra of 3Cz-Ph-CN and 3Cz-mPh-CN. (e) EL spectra of 3Ph-Cz-CN at different voltages (inset is the picture of device C at the voltage of 12 V). (f) PL spectrum of the blend film (inset is the description of CIE in the nondoped device C).