Patent Application
20070248840
Referring to
According to one embodiment of the present invention, the substrate 10 is made of suitable glass, such as quartz glass, soda-lime glass or flexible material. The material used for the first electrode 12 is such as, for example, indium-tin oxide (ITO), indium-zinc oxide (IZO), aluminum-zinc oxide (AZO) and the like that has a thickness in a range from about 50 nm to about 600 nm. The hole-transporting layer 14 uses a suitable conductive polymeric material, e.g., polyaniline, PEDOT/PSS produced by Bayer AG, which is an aqueous dispersion of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate), and the like that has a thickness in a range from about 0.5 nm to about 250 nm.
The host material for the light-emitting layer 16 may be poly(p-phenylenevinylene) (PPV), polyvinylcarbazole (PVK), poly{2,7-[9,9-di(alkyl)fluorine]} or poly(alkylthiophene)derevatives, all of which are single-layer conductive polymer with photo-crosslinkable groups included in the functional groups on the main or side chains. The light-emitting material for the light-emitting layer 16 may be at least one small-molecule light-emitting dye, such as a blue light-emitting material 4,4′-bis[2-(4-(N,N-diphenylamino)phenyl)vinyl]biphenyl (DPAVBi), IDE 102 produced by Idemitsu (Japan) and the like, a green light-emitting material 10-(2-Benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-11-one (C545T) and the like, and a red light-emitting material 4-(Dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) and the like. The host material and the light-emitting material may be mixed in a solvent, in particular in an organic solvent. The color purities of those red light-emitting materials in state of the art are not ideal. For example, as DCJTB deviates towards orange color, it may be used together with rubrene to have a color shift to red. The light-emitting layer 16 may have further material mixed therein, which is such as Tris(8-hydroxyquinoline)aluminum (Alq3), 1,2,4-triazole-3-alanine (TAZ), Bis(2-methyl-8-quinolinolato-N1,O8)-(1,1′-Biphenyl-4-olato)aluminum (Balq), 2-(4′-biphenyl)-5-(4″-tert-butylphenyl)-1,3,4-oxadiazole (PBD) and the like for matching the energy barriers and improving the thermal stability and film-forming performance. In the method of forming the light-emitting layer 16 for the polymeric electroluminescent device according to the present invention, the uncured portion of the host material mixed with the at least one small-molecule light-emitting material may be removed by washing with a solvent, in particular with an organic solvent. The light-emitting layer 16 may have a thickness in a range from about 0.5 nm to about 250 nm. The content of the at least one small-molecule light-emitting material in the light-emitting layer 16 is from about 0.001% to about 50% by weight.
The hole-blocking layer 18 may use small-molecule materials such as 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), 2,2′,2″-(1,3,5-benzenetriyl)-tris(1-phenyl-1H-benzimi-dazole (TPBI) and the like, or polymeric materials such as poly(9,9-dioctyl-fluorene)/poly[9,9-dioctylfluorene-co-bis-N-(4-butylphenyl)diphenylamine] (F8/TFB) and the like, with a thickness in a range from about 0.5 nm to about 100 nm.
The electron-transporting layer 20 may use Alq3, TAZ, BAlq, PBD and the like with a thickness in a range from about 0.5 nm to about 200 nm, for matching the energy barriers and improving the thermal stability and film-forming performance.
The electron-injecting layer 22 may be made of lithium fluoride, strontium fluoride, strontium, lithium and the like, with a thickness in a range from about 0.01 nm to about 200 nm.
The second electrode 24 may be a single-layer structure made of aluminum, silver and the like, or a multi-layer comprising, such as, calcium/aluminum, barium/aluminum, calcium/magnesium: aluminum, barium/magnesium: aluminum and the like.
A full-color display device according to the embodiment described above may be made in the following steps (referring to
Washing the substrate 10 and the first electrode 12 formed thereon by means of supersonic cleaning with an organic solvent or de-ionized water, nitrogen blowing, vacuum drying at a temperature ranging from about 80° C. to about 200° C., UV ozone stripping and oxygen plasma stripping.
A plurality of subpixels is formed by coating a photo-sensitive insulating polymeric material onto the substrate 10 and the first electrode 12. The patterned photo-sensitive insulating polymeric material is formed by the photolithography process. A plurality of subpixels with apertures 13 and spacers 13′ is formed and each subpixel corresponds to an organic electroluminescent device.
The hole-transporting layer 14 is formed by spin coating PEDOT/PSS and then is baked in an inert gas atmosphere.
The light-emitting layer 16 is formed by spin coating the green light-emitting material 15, which has been dissolved in a suitable amount of xylene. The green light-emitting material 15 includes PVK, C545T amounting to about 2% by weight for light-emitting, and Alq3 amounting to about 20% by weight for matching the energy barriers and improving the thermal stability and film-forming performance (referring to
The subsequent layers, i.e., the hole-blocking layer 18, the electron-transporting layer 20, the electron-injecting layer 22 and the second electrode 24 are formed by vacuum evaporation. The material for the hole-blocking layer 18 is TBPI, the material for the electron-transporting layer 20 is Alq3, the material for the electron-injecting layer 22 is lithium fluoride and the material for the second electrode 24 is aluminum.
A water/oxygen-barrier thin film is formed on the second electrode 24 by vacuum evaporation. A glass cover plate is disposed on the film with the sides configured by the substrate 10. The cover plate is coated with seal and is cured by heating in order to form a package.
After the package is formed, it is then tested. A luminescence meter PR 650 produced by PhotoResearch is used to read out the data for the present embodiment and a typical software for measuring OLED's photonic characteristics is used to analyze the data.
The following tables provide a comparison of the result with that set forth in the report by Becker, et al, SID 03 Digest, pp. 1286-1289. Table 1 compares the power efficiencies of the electroluminescent devices for the three primary colors, where the power efficiency is defined as the ratio of the luminous flux to the power consumed under current density of 50 mA/cm2. Table 2 compares the luminescences.
Moreover, the CIE chromaticity coordinates of the electroluminescent devices for the three primary colors are (0.30, 0.63) for the green, (0.65, 0.35) for the red and (0.15, 0.27) for the blue.
Accordingly, in the polymeric electroluminescent device of the present invention that may be obtained by spin coating for full color displaying because its transport property of the carriers is unchanged after photo-crosslinking. The polymeric host material for the light-emitting layer is not substantially the light-emitting source so that its distribution of molecular weight does not affect the color purity and. Furthermore, the at least one small-molecule light-emitting material may emit light as it receives energy from the host material that undergoes excitation and de-excitation by energy transferring or carrier trapping.
While the invention has been described in detail with certain preferable embodiments, this description is not intended to limit the invention for which other embodiments may be possibly employed. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the invention as hereinafter claimed.
| Number | Date | Country | Kind |
|---|---|---|---|
| 095114069 | Apr 2006 | TW | national |
