Dislocated output coupling within a selected band in an OLED based on an in-plane DBR microcavity array

Abstract

Periodic arrays of microcavities based on distributed Bragg reflectors (DBR) are introduced into organic light-emitting diodes (OLEDs). The electroluminescence (EL) confined both within the DBR microcavity and inside the indium-tin-oxide layer is coupled out through interacting with the grating structures, so that a narrow-band portion of the EL is picked up by multiple grating-diffraction processes with the aid of the waveguide effect in the substrate. This selected EL spectrum is coupled out of the device at a separated location with a distance larger than 4 mm from the direct output for a substrate with a thickness of 1.1 mm. Meanwhile, optical gain inside the microcavity and through inter-microcavity coupling leads to the amplification of the EL, so that band-narrowing effect is observed with increasing the applied voltage for the dislocated output. A narrowest bandwidth of 26 nm was measured for the dislocated output coupling, which is a significant narrowing with respect to the direct output with a bandwidth >100 nm.