An organic electroluminescence device using exciplexes as host materials

Abstract

The present invention relates to an organic electroluminescent device using an exciplex as a host material, in particular to an organic electroluminescent device comprising a host material and a fluorescent material. Wherein the host material comprises a first organic compound and a second organic compound; the mixture or interface formed by the first organic compound and the second organic compound generates an exciplex under the condition of light excitation or electric field excitation; the formed exciplex There is an effective overlap between the emission spectrum of the fluorescent dopant material and the absorption spectrum of the fluorescent dopant material, forming effective energy transfer; and the first organic compound and the second organic compound have different carrier transport characteristics; wherein the fluorescent material is an organic compound containing boron atoms compound. The organic electroluminescent device prepared by this method has the characteristics of high efficiency and long life.

Description

technical field [0001] The invention relates to the technical field of semiconductors, in particular to an organic electroluminescent device with high color purity, high efficiency and long life. 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 displays and have attracted widespread attention because they can achieve ultra-thin and ultra-light weight, fast response to input signals, and low-voltage DC drive. [0003] It is considered that the organic electroluminescent device has the following light emitting mechanism: when a voltage is applied between the electrodes sandwiching the light emitting layer, the electrons injected from the anode and the holes injected from the c...

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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

The efficiency of the device rolls off seriously at high current density

[0009] (4) In the traditional main fluorescent 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 composite 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

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