Patent Application
20070298283
This invention is better understood by referring to the accompanying drawings, wherein:
A preferred embodiment of a fabrication method of an indium tin oxide (ITO) anode containing nickel for improving injection efficiency of an organic light emitting diode (OLED) is shown in
The method includes various processes. A first process is to prepare an ITO substrate with an anode, and a second process is to deposit an ITO film on the anode via direct current magnetron sputtering. Next, a third process is to prepare a single-target source of ITO containing nickel, and a fourth process is to sputter the single-source of the ITO containing nickel on the ITO film originally not mingled with nickel, forming an ITO film mingled with nickel. The temperature of the ITO substrate is controlled between 25-200° C. during sputtering process and the ITO film is successively annealed to about 150° C. for 10 minutes to 2 hours under vacuum.
Moreover, the nickel contained in the single-target source of the ITO film has 1%, 3%, or 5% by weight ratio to the ITO.
Of course, an ITO film mingled with nickel and formed by the process mentioned above should further include at least a hole transport layer formed on the anode of the substrate and an electron transport layer formed on the hole transport layer if applied for an OLED.
It has been proved experimentally that the work function of the anode of the ITO film containing nickel is higher than that of a pure ITO film (approx. 4.6 eV). In addition, different work functions have been achieved when different conditions, such as sputtering power of nickel, have been tested in this invention. So far, the work function of the anode of the ITO film containing nickel is as high as 5.8 eV, able to tremendously lessen a potential barrier between the anode of the ITO and the hole transport layer, reducing about 1.8V of threshold voltage and turn-on voltage of an OLED device, advancing a hole injection efficiency.
As described above, when the invention is applied to a low-voltage driving OLED, it can increase lighting efficiency about 30% because of a highest recombination efficiency of the hole and the electron. Furthermore, the roughness of the ITO anode is improved owing to the employment of nickel, able to effectively reduce productivity of black pixel after the OLED is driven, relatively lengthening the life of the OLED.
The substrate mentioned previously can be replaced with glass, plastics and the like, as long as able to obtain the same or similar effects.
Next, the structure of an ITO anode for an OLED includes an ITO substrate provided with an anode mingled with nickel, a hole transport layer formed on the anode of the ITO substrate, and an electron transport layer formed in the hole transport layer.
While the preferred embodiment of the invention has been described above, it will be recognized and understood that various modifications may be made therein and the appended claims are intended to cover all such modifications that may fall within the spirit and scope of the invention.
