Organic light-emitting diode and preparation method thereof, display substrate, and display apparatus

Abstract

The invention discloses an organic light-emitting diode (OLED) and a preparation method thereof, a display substrate, and a display apparatus. The organic light-emitting diode is composed of an anode, a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer and a cathode. The cathode is made of a transparent conductive oxide material layer. An energy level transition layer is formed between the electron transport layer and the cathode and is used for carrying out energy level transition between the electron transport layer and the cathode, thereby reducing the difficulty of the electron injection. Compared with the OLED device in the prior art, the electron injection of the OLED device becomes easy and the operating voltage of the OLED device is substantially reduced, thereby substantially improving the service life of the OLED device and solving problems of short service life and over large operating voltage of the OLED device due to mismatching of the TCO process or energy level.

Description

technical field [0001] The invention relates to the field of display technology, in particular to an organic light emitting diode (OLED) and a preparation method thereof, a display substrate, and a display device. Background technique [0002] With the development of multimedia technology and the continuous improvement of informatization, people have higher and higher requirements on the performance of flat panel display devices. Compared with liquid crystal displays, organic electroluminescent displays have a series of advantages such as self-illumination, low-voltage DC drive, full curing, wide viewing angle, and rich colors. Low power consumption, its response speed can reach 1000 times that of liquid crystal display, but its manufacturing cost is lower than the liquid crystal display of the same resolution, therefore, organic electroluminescent display has a broader application prospect. [0003] An organic electroluminescent diode (OLED) is a light-emitting device that...

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Problems solved by technology

[0005] For top-emitting OLED devices, thin metal is generally used as the cathode material at the top, but the conductivity of the device will be poor if the metal cathode is too thin, and it will form a microcavity effect, making the optical design of the device very complicated, so often Replacing thin metals with transparent conductive oxides (TCOs) as cathodes for top-emitting OLED devices

Currently commonly used TCO materials include indium tin oxide (ITO), indium zinc oxide (IZO) and other materials, but these TCO materials are usually suitable for making anodes, so TCO materials are used as cathodes to increase the transparency of top-emitting OLED devices. When the rate is exceeded, the life of these materials will be greatly reduced and the operating voltage will be greatly increased due to the mismatch between the work function of these materials and the lowest unoccupied molecular orbital (LUMO) energy level of the electron transport layer (ETL). For example, if it is made of IZO Cathode, because the work function of IZO is about 5eV, it is quite different from the LUMO energy level of the general electron transport layer, such as image 3 As shown, it will make electron injection difficult, the operating voltage of OLED devices will increase, and the lifetime will decrease.

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