Patent Application
20080001537
The present invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:
The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. The scope of the invention is best determined by reference to the appended claims. Embodiments of the invention, which provides an organic light emitting device, will be described in greater detail by referring to the drawings that accompany the invention. It is noted that in the accompanying drawings, like and/or corresponding elements are referred to by like reference numerals.
Next, a hole-injecting layer 306, such as CuPc, TiOPc, m-MTDATA and/or 2-TNATA, is formed on the substrate 302 and the anodes 304. A hole-transporting layer 308, such as TPD, NPB (Kodak), PVK, Spiro-TPD (Convion) and/or Spiro-NPB (Convion) is formed on the hole-injecting layer 306. An organic luminescent material layer 310, such as Alq3, Almq3, Blue (Ricoh) and/or TBADN (Kodak) is formed on the hole-transporting layer 308. An electron-transporting layer 312, such as Alq3, Almq3, DVPBi (Idemitsu), TAZ (Sumitomo) and/or PBD (Idemitsu) is formed on the organic luminescent material layer 310. An electron-injecting layer 314, such as LiF, MgP, MgF2 and/or Al2O3 is formed on the electron-transporting layer 312.
A primary cathode layer 316, such as Ag, Al, Li, Ca, In, ITO and/or IZO is formed on the electron-injecting layer 314, for example by evaporation or sputtering. The combination of the hole-injecting layer 306, hole-transporting layer 308, organic luminescent material layer 310, electron-transporting layer 312 and electron-injecting layer 314 can be referred to as an organic light emitting layer 309 (OLED layer), in which can be achieved by evaporation, spin coating or other method. The primary cathode layer 316 can be a metal layer formed by evaporation. The primary cathode layer 316 can also be a transparent conductive layer, such as ITO or IZO formed by sputtering. The combination of the anodes 304, the hole-injecting layer 306, the hole-transporting layer 308, the organic luminescent material layer 310, the electron-transporting layer 312 and the electron-injecting layer 314 and the primary cathode layer 316 can be referred to as pixels 311, as shown in
In order to reduce damage of the OLED layer 309 from ion sputtering, thickness of the primary cathode layer 316 can not be too thick. In a embodiment of the invention, the primary cathode layer 316 is about 20 Ř500 Åthick. Resistance of the primary cathode layer 316, however, increases, when reducing thickness thereof. In order to eliminate the issues, in an embodiment of the invention, a plurality of patterned auxiliary cathodes 318 are formed on the primary cathode layer 316. The patterned auxiliary cathodes 318 are strips interposed between each two rows of pixels 311 and extend in a row direction for a distance of at least the length of two pixels 311. Note that the patterned auxiliary cathodes 318 are connected to a conductive pad 320 thereunder for supplying current (electrons and/or holes) to the pixels 311 for illumination. The patterned auxiliary cathodes 318 can be conductive materials, such as Ag, Al, Li, Ca, In, ITO and/or IZO. In a embodiment of the invention, the patterned auxiliary cathodes 318 are formed of Al, Ag or combination thereof, and about 1000 Ř7000 Å. In another embodiment of the invention, the patterned auxiliary cathodes 318 can be a conductive line. In addition, the patterned auxiliary cathodes 318 is thicker than the primary cathode layer 316, thus, the patterned auxiliary cathodes 318 has lower resistance than the primary cathode layer 316.
Accordingly, electrons and/or holes can be transported from the conductive pad 320 to the patterned auxiliary cathodes 318 with lower resistance, and then further to the pixels 311. Due to the patterned auxiliary cathodes 318 with lower resistance, the primary cathode layer 316 can be thinner to reduce affection of the underlying OLED layer 309, and electrons and/or holes can be transported to pixels with less resistance.
Referring to
The invention is not limited to the described double-emitting OLED devices. In one embodiment of the invention, the feature described can be used in top-emitting OLED devices.
According to the embodiments described, the primary cathode layer 316 can be formed with thinner thickness to reduce damage to the underlying OLED layer 309. Due to the low resistance of the patterned auxiliary cathodes 318 interposed between each two rows of pixels 311, current can be more easily transported to the pixels 311 away form the conductive pads 320. Therefore, non-uniformity from different electron transporting path between pixels 311 away and near the conductive pads could be eliminated. Therefore, non-uniformity issues of illumination between pixels 311 could be eliminated.
While the invention has been described by way of example and in terms of the preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, it is intended to cover various modifications and similar arrangements (as would be apparent to those skilled in the art). Therefore, the scope of the appended claims should be accorded the broadest interpretation so as to encompass all such modifications and similar arrangements.
