Effect of the thickness of blue emitting layer on organic light-emitting devices

Organic light-emitting devices based on the blue fluorescent 4,4´-bis(2,2´-diphenylvinyl)-1, 1´-biphenyl(DPVBi) and red phosphorescent tris(1-pheny-lisoquinolinolato-C², N)iridium(III) [Ir(piq)₃] emitters were fabricated, with a structure of ITO/ NPB (40 nm)/ DPVBi (d)/ CBP: Ir(piq)₃ (15 nm, 6%)/Bphen (40 nm)/Mg:Ag (200 nm). The effect of the thickness variation of the DPVBi on the device performance was studied. The results showed that, the device with 5-nm DPVBi had relatively higher luminance and current efficiency, while the device performance was reduced as increasing the thickness of DPVBi. Moreover, as for the device with thicker DPVBi, stronger blue emission than red emission can be observed in the electroluminescent spectra.