Dipole-Controlled Matrix for Phosphorescent OLED Efficiency
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Solution Overview
Problem
Polyfluorenes are not suitable as a matrix for light emitting devices emitting shorter wavelengths than green due to their small lowest triplet excitation energy, resulting in insufficient luminescent efficiency when used with triplet emitting compounds.
Innovation Solution
A composition comprising a phosphorescent compound and a compound with a structure containing three or more repeating units having a dipole moment of 1.0 Debye or more, where the dipole moment ratio of dimer structures satisfies specific conditions, enhancing luminescent efficiency by controlling dipole moment alignment and charge injection transportability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If polyfluorenes are used as a matrix for light emitting devices, then a film can be formed by coating, but the luminescent efficiency is insufficient for shorter wavelength than green light emission due to small lowest triplet excitation energy
Solution Approach 1:
The invention changes the chemical structure parameters of the matrix material from polyfluorenes to compounds with specific dipole moment characteristics (D1a² + D1b² ≤ D2²). This parameter change in the matrix structure enables it to effectively transfer triplet excited states to phosphorescent compounds, thereby improving luminescent efficiency while maintaining film formation capability through coating processes.
Solution Approach 2:
The invention creates a composite light emitting material system consisting of a specifically structured matrix compound and phosphorescent compounds. The matrix compound with controlled dipole moment alignment works synergistically with the phosphorescent compounds to achieve high luminescent efficiency in green to blue light emission, resolving the contradiction between ease of manufacture and energy efficiency.
2Ease of manufacture
If polyfluorenes are used as a matrix with triplet emitting compounds, then film formation is achieved, but light emission from the triplet light emitting compound is weak
Solution Approach 1:
The invention modifies the matrix material parameters by selecting compounds whose dipole moments satisfy D1a² + D1b² ≤ D2², ensuring proper orientation for triplet state transfer. This parameter optimization enables strong light emission from phosphorescent compounds while preserving the ease of film formation through coating, directly addressing the contradiction between manufacturability and illumination intensity.
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 solution achieves excellent luminescent efficiency in light emitting devices, particularly for green to blue light emission, by optimizing the dipole moment alignment and lowest triplet excitation energy, leading to improved light emission and charge transport properties.
Implementation Method 1
a phosphorescent compound showing light emission from the triplet excited state
Implementation Method 2
a compound having a structure containing three or more repeating units having a dipole moment magnitude of 1.0 Debye or more connected in series, wherein the proportion of the number of dimer structures in which the magnitude D2 of the dipole moment of the dimer structure, the magnitude D1a of the dipole moment of the first repeating unit constituting the dimer structure and the magnitude D1b of the dipole moment of the second repeating unit constituting the dimer structure satisfy a relation represented by the following formula (A): D1a2 and D1b2 (A) is 50% or more
Data Source
AI summary
A composition comprising a phosphorescent compound, and a compound having a structure containing three or more repeating units having a dipole moment dimension of 1.0 Debye or more connected in series,wherein, based on the total number of dimer structures composed of any two repeating units connected in series contained in the above-described structure, the proportion of the number of dimer structures in which the dimension D2 of the dipole moment of the dimer structure, the dimension D1a of the dipole moment of the first repeating unit constituting the dimer structure and the dimension D1b of the dipole moment of the second repeating unit constituting the dimer structure satisfy a relation represented by the following formula (A):D1a<D2 and D1b<D2 (A)is 50% or more.