We have successfully fabricated a low-reflection organic light-emitting diode (LR-OLED) by replacing the highly reflective Al cathode of a conventional OLED with a Fabry–Pérot (FP) cavity cathode, which is simultaneously responsible for absorption, plasmonic absorption and destructive interference. The FP cavity cathode consisted of a front semi-transparent double thin metal layer (Al/Ag), an inserted organometallic black layer (BL) in the middle and a highly reflective Al mirror. The organometallic BL contained a high-mobility electron transport and broadband absorptive organic matrix, N,N′-bis(2,6-diisopropylphenyl)-1,7-bis(4-methoxy-phenyl)perylene-3,4,9,10-tetracarboxydiimide (MPPDI), and Ag-nanoparticle (NP) dopants which contributed not only to the plasmonic absorption but also to the metallic conductivity. By adjusting the thickness and Ag-NP concentration of the organometallic BL, one can optimize the destructive interference cavity effect. LR-OLEDs fabricated using the aforementioned characteristics of the Ag-NP yielded superior electrical performance and low reflection across almost the entire visible spectrum. With the exemption of surface reflection (air/glass ∼4%), a lowest reflection of 0% near 750 nm and an average reflection of 1.39% for the entire visible spectrum were obtained for a LR-OLED with a 65 nm organometallic BL (mixing ratio of MPPDI : Ag = 10 : 1). With the additional structural cavity cathode, the LR-OLEDs nonetheless exhibited similar electrical performances and continuous operational lifetimes to those of control devices with a traditional highly reflective Al cathode.

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Under a white ambient light illumination and without bias, the color-cathode organic light emitting device (OLED) shows the various reflection colors to display the information by utilizing the internal interference cavity inside rear cathode. In this report, we employed a high conductivity metal-organic material, tris(8hydroxyquinolinato)aluminum (Alq3) doped with Ag nanoparticles, to be the interlayer of this interference cavity cathode. Its good conductivity is leading to a comparable electrical performance with that of reference device. There is a small increase of driving voltage 0.5V at 100 mA/cm2 for colorcathode OLED. In addition, the thicknesses of this interlayer inside this interference cavity varies to 40, 60, 80 and 100 nm to alter the reflection colors such as orange, purple, blue and green.