Multilayer White Light-Emitting Organic Electroluminescent Device

Abstract

Organic electroluminescent devices are light-emitting diodes in which the active materials consist entirely of organic materials. Here, the fabrication of a white light-emitting organic electroluminescent device made from vacuum-deposited organic thin films is reported. In this device, three emitter layers with different carrier transport properties, each emitting blue, green, or red light, are used to generate white light. Bright white light, over 2000 candelas per square meter, nearly as bright as a fluorescent lamp, was successfully obtained at low drive voltages such as 15 to 16 volts. The applications of such a device include paper-thin light sources, which are particularly useful for places that require lightweight illumination devices, such as in aircraft and space shuttles. Other uses are a backlight for liquid crystal display as well as full color displays, achieved by combining the emitters with micropatterned color filters.

Solution-processed multilayer small-molecule light-emitting devices with high-efficiency white-light emission

“…4c). Alternatively, with three-coordinated tris(2-(4,6-difluorophenyl)pyridine)iridium(III) (Ir(Fppy) 3 ), the device efficiencies significantly increased to 36 lm W À 1 for power efficiency and 20% for EQE at 100 cd m À 2 (Fig. 4c, Supplementary Table 1).…”

“…It is intriguing to note that Ir(Fppy) 3 performs five times as well as FIrpic in power efficiency, although these two blue emitters possess almost identical opto-electrical properties (Supplementary Table 2). In these devices, the majority of excitons would be generated near the EML/ETL interface because of the relatively large injection barrier between them (Fig.…”

“…By using the two molecules as hosts for tris(2-phenylpyridine) iridium(III) (Ir(ppy) 3 ), we fabricated green phosphorescent OLEDs, in which quadruple organic layers were fully solution processed. The device configuration was indium tin oxide (ITO) (130 nm)/poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) (30 nm)/poly(9,9-dioctyl-fluorene-alt-N-(4-butylphenyl)-diphenylamine) (TFB) (20 nm)/host:12 wt% Ir(ppy) 3 (30 nm)/2,2 0 ,2 00 -(1,3,5-benzinetriyl)tris(1-phenyl-1-H-benzimidazole) (TPBi) (50 nm)/lithium 8-quinolate (Liq) (1 nm)/Al (100 nm) (Fig.…”

“…Such multilayer structures allow for the separation of the charge-injecting, chargetransporting and light-emitting functions to the different layers, thus leading to a marked increase in efficiency and lifetime [1][2][3][4][5] . Although stepwise vacuum evaporation easily achieves the required multilayer structures of small molecules at the expense of high manufacturing cost, it is more challenging in the case of solution processing, because depositing one layer would dissolve the layer beneath it.…”

Inhibition of solution-processed 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile crystallization by mixing additives for hole injection layers in organic light-emitting devices

“…[1][2][3] To fabricate highly efficient devices, the incorporation of hole injection layers (HILs) is indispensable because these significantly improve the characteristics of hole injection from the anode to the emitting layer, leading to lower driving voltages and improved charge recombination balance. To date, various HILs have been reported, [4][5][6][7][8][9][10][11][12][13][14][15] and, among these, 1,4,5,8,9, 11-hexaazatriphenylene-hexacarbonitrile (HAT-CN) has been employed in HILs (leading to low driving voltage) 4,[16][17][18][19][20][21][22] since the first application of OLED by LG Chemical Ltd. 22 HAT-CN was first reported by Czarnik and co-workers 23 and its characterization has been investigated in various studies.…”