Fluoranthene Derivative Compound for Blue OLED Luminous Efficiency
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Solution Overview
Problem
Existing organic electroluminescence devices have insufficient luminous efficiency, particularly when using TADF compounds, perylene derivatives, benzofluoranthene derivatives, or benzo[k]fluoranthene derivatives as luminescent materials.
Innovation Solution
A compound represented by a specific formula is introduced, which, when used in the emitting layer of an organic electroluminescence device, enhances luminous efficiency by exhibiting a higher molar absorbance coefficient and smaller Stokes shift compared to traditional compounds like TBPe, effectively transferring recombination energy and improving blue wavelength region performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If TADF compounds, perylene derivatives, benzofluoranthene derivatives, or benzo[k]fluoranthene derivatives are used as luminescent materials in organic electroluminescence devices, then the devices can emit light in the blue wavelength region, but the luminous efficiency is insufficient
Solution Approach 1:
The patent applies parameter changes by modifying the molecular structure of the luminescent material through specific chemical substitutions (introducing electron-withdrawing groups like fluorine, cyano, or carbonyl groups at specific positions of the fluoranthene core). These structural parameter changes result in optimized HOMO-LUMO energy levels, increased molar absorbance coefficients, and reduced Stokes shifts, thereby improving luminous efficiency while maintaining blue wavelength emission.
Solution Approach 2:
The patent employs composite materials by combining the synthesized fluoranthene derivatives with host materials (such as mCP, TCTA, or TAPC) in specific weight ratios (typically 1:9 to 4:6). This composite approach creates an emitting layer where the guest luminescent material and host material work synergistically to achieve high luminous efficiency through effective energy transfer and improved charge carrier balance.
2Productivity
If traditional luminescent materials are used, then the device structure is simpler, but the molar absorbance coefficient is lower and Stokes shift is larger, reducing energy transfer efficiency
Solution Approach 1:
The patent systematically varies molecular parameters including substituent types (F, CN, COOH, CHO), substitution positions (2, 7, 9 positions of fluoranthene core), and substituent numbers to optimize the balance between absorbance coefficient, Stokes shift, and energy transfer efficiency. This parameter optimization achieves high productivity without excessive device complexity.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The compound significantly improves the luminous efficiency of organic electroluminescence devices, particularly in the blue wavelength region, by enhancing energy transfer and emission efficiency.
Implementation Method 1
When a voltage is applied to an organic electroluminescence device, holes are injected from an anode into an emitting layer and electrons are injected from a cathode into the emitting layer. The injected electrons and holes are recombined in the emitting layer to form excitons.
Implementation Method 2
A fluorescent organic EL device uses emission caused by singlet excitons. The compound exhibits a higher molar absorbance coefficient and smaller Stokes shift, effectively transferring recombination energy and improving blue wavelength region performance.
Implementation Method 3
The TADF mechanism uses such a phenomenon that inverse intersystem crossing from triplet excitons to singlet excitons thermally occurs when a material having a small energy difference (AST) between singlet energy level and triplet energy level is used.
Data Source
AI summary
A compound is represented by a formula (20) below. In the formula (20), a least one pair of a pair of X21 and X22, a pair of X22 and X23 and a pair of X23 and X24 are carbon atoms to be bonded to the structure represented by the formula (20a),