White light emission induced by confinement in organic multiheterostructures

Abstract

A technique for inducing white-light emission from organic multiheterostructures is proposed. The configuration of organic multiheterostructure white-light emitting diodes is ${\mathrm{ITO/TPD(50 nm)/BePP}}_{\mathrm{2}}{\mathrm{(5 nm)/TPD(4 nm)/BePP}}_{\mathrm{2}}\mathrm{:rubrene(5 nm)/}$ ${\mathrm{TPD(4 nm)/Alq}}_{\mathrm{3}}\mathrm{(10 nm)/Al}.$ Triphenyldiamine derivative (TPD) is used as a hole-transporting layer and the potential barrier layers. Blue fluorescent phenylpyridine beryllium $({\mathrm{BePP}}_{\mathrm{2}}\mathrm{),}$ orange fluorescent rubrene, and green fluorescent aluminum complex $({\mathrm{Alq}}_{\mathrm{3}})$ are used as three primary colors. ${\mathrm{BePP}}_{\mathrm{2}}$ and ${\mathrm{BePP}}_{\mathrm{2}}$ doped with rubrene act as the potential wells sandwiched between TPD barrier layers, in which excitons are confined. ${\mathrm{Alq}}_{\mathrm{3}}$ is used as an electron-transporting green-color emitter. The white-light emission spectrum covers a wide range of the visible region, and the Commission Internationale de l’Eclairage coordinates of the emitted light are (0.32, 0.38) at 9 V. The maximum brightness and luminous efficiency of this device are $\text{4000\hspace{0.05em}}{\mathrm{cd/m}}^{\mathrm{2}}$ (at 17 V) and 0.4 lm/W, respectively.