OLED Host Composition for Deep-HOMO Red Phosphorescent Emitters
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Solution Overview
Problem
Current organic light-emitting diode (OLED) technologies face challenges in finding suitable host compounds for red phosphorescent emitters with deep highest occupied molecular orbital (HOMO) levels, as they require specific energy level matching and compatibility to achieve efficient light emission.
Innovation Solution
Development of a composition comprising a first compound with a specific structure and a second compound that functions as a phosphorescent emitter, where the highest occupied molecular orbital (HOMO) energy level of the second compound is equal to or less than −5.1 eV, and the difference in HOMO energy levels between the two compounds is less than 0.3 eV, enabling efficient light emission with a peak wavelength of 550 nm or greater.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional host compounds are used for red emitters with deep HOMO levels, then the device structure can be maintained, but luminance efficiency is insufficient due to poor energy level matching
Solution Approach 1:
The patent modifies the HOMO energy level parameter of the host compound by introducing a dibenzofuran moiety fused to the xanthene core, achieving a HOMO level of −5.1 eV or lower. This parameter change enables proper energy level matching with red phosphorescent emitters, thereby improving luminance efficiency without compromising device structure
Solution Approach 2:
The patent creates a composite host compound structure by fusing dibenzofuran (a heterocyclic aromatic compound) with the xanthene core. This composite structure combines the deep HOMO level characteristic of dibenzofuran with the emissive properties of xanthene, achieving both energy level compatibility and efficient light emission
2Reliability
If the HOMO energy level of the host compound is increased to match deep HOMO level emitters, then energy level compatibility improves, but the emission spectrum may extend into unwanted long wavelengths
Solution Approach 1:
The patent carefully controls the HOMO energy level parameter at −5.1 eV or lower while managing the triplet energy level to prevent excessive redshift. The dibenzofuran-xanthene structure achieves this balance by providing sufficient electron-withdrawing character for deep HOMO level while maintaining appropriate rigidity and conjugation to limit long-wavelength emission
Solution Approach 2:
The patent introduces the dibenzofuran moiety as a specific local structural feature on the xanthene core. This local modification provides the necessary electron-withdrawing character and deepens the HOMO level without requiring extensive changes to the entire molecular structure, thereby maintaining control over the emission spectrum and minimizing long-wavelength photon generation
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 proposed solution results in improved luminance efficiency and reduced long-wavelength photons, enhancing the performance of OLEDs by using a host compound that effectively supports red emitters with deep HOMO levels, leading to lower operating voltage and higher external quantum efficiency.
Implementation Method 1
The second compound is capable of functioning as a phosphorescent emitter at room temperature and emits light with a peak emission wavelength equal to or greater than 550 nm
Implementation Method 2
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
A composition is disclosed that includes a first compound capable of functioning as a host in an emissive layer of an OLED at room temperature; and a second compound that includes a ligand LA of Formula IIIwhere ring A is a 5-membered or 6-membered carbocyclic or heterocyclic ring; where R represents two adjacent substituents that are joined together to form a ring that is fused to ring B, and R has a structure of Formula IVor Formula Vdisclosed herein.