Organic electroluminescent device based on exciplex and excimer system

Abstract

The invention relates to an organic electroluminescent device based on an exciplex and excimer system. A light emitting layer host material includes first, second and third organic compounds. A mixture or lamination interface formed by the first organic matter and the second organic matter generates an exciplex under optical or electric excitation. The third organic compound is doped in a mixtureformed by the first organic compound and the second organic compound or a layer of a laminated interface, and the third organic compound forms an excimer. The singlet energy level of the exciplex is higher than that of the third organic compound, and the triplet energy level of the exciplex is higher than that of the third organic compound. The singlet energy level of the excimer is higher than that of the object material, and the triplet energy level of the excimer is higher than that of the object material. The first organic compound and the second organic compound have different carrier transport characteristics, and the object doping material is a fluorescent compound. The device has the characteristics of high efficiency and long service life.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to a high-efficiency, long-life organic electroluminescent device based on an exciplex and an excimer system. Background technique [0002] Organic light emitting diodes (OLEDs) have been actively researched and developed. The simplest basic structure of an organic electroluminescent device consists of a light emitting layer sandwiched between opposing cathode and anode. Organic electroluminescent devices are considered to be the next generation of flat panel display materials and have attracted widespread attention due to their ultra-thin, ultra-light weight, fast response to input signals, and low-voltage DC drive. [0003] It is generally believed that organic electroluminescent devices have the following light-emitting mechanism: when a voltage is applied between electrodes sandwiching a light-emitting layer, electrons injected from the anode and holes injected from the ...

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Problems solved by technology

[0006] Although theoretically TADF materials can achieve 100% exciton utilization, there are actually the following problems: (1) The T1 and S1 states of the designed molecules have strong CT characteristics, and the very small S1-T1 state energy gap, although it can A high T1→S1 state exciton conversion rate is achieved through the TADF process, but at the same time it leads to a low S1 state radiative transition rate. Therefore, it is difficult to achieve both (or simultaneously) high exciton utilization efficiency and high fluorescence radiation efficiency;

[0007] (2) Due to the current use of TADF materials with D-A, D-A-D or A-D-A structures, due to their greater molecular flexibility, the configuration of molecules in the ground state and excited state changes greatly, and the half-maximum width (FWHM) of the spectrum of the material is too large. Large, resulting in a reduction in the color purity of the material;

[0008] (3) Even if doped devices have been used to alleviate the T-exciton concentration quenching effect, the efficiency of most TADF materials has a serious roll-off at high current densities

[0009] (4) In the traditional host-guest collocation method, due to the different electron and hole transport rates of the host material, the carrier recombination rate is reduced, resulting in a decrease in device efficiency; at the same time, the carrier complex area is close to the side of the host material, The carrier recombination area is too concentrated, resulting in too concentrated triplet base density, resulting in obvious carrier quenching, and reduced device efficiency and lifetime

However, there are still insufficient carrier recombination and low device efficiency and lifetime.

At the same time, the half-peak width of the device spectrum is large, which is not conducive to the improvement of the color purity of the device

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