Tetradentate OLED Materials for Horizontal Emitter Orientation
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Solution Overview
Problem
Existing OLEDs face challenges in achieving high efficiency and maximizing light extraction due to limitations in the orientation and arrangement of phosphorescent emitters, which affect their external quantum efficiency.
Innovation Solution
Incorporation of organometallic complexes with a large aspect ratio in one direction, such as Ir, Os, Rh, Ru, Re, Pt, or Pd compounds with bis- or tris-heteroleptic ligands, that preferentially orient themselves horizontally to enhance light extraction by maximizing the surface area facing the light-emitting façade.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional phosphorescent emitters are used in OLEDs, then the device structure is simple, but the external quantum efficiency is limited due to poor light extraction
Solution Approach 1:
The patent employs asymmetric host-guest complexes with specific ligand arrangements (e.g., C^N^C^N tetradentate ligands) that create anisotropic charge distribution and dipole moments. This asymmetry in molecular structure leads to preferential orientation of the emitters, improving light extraction efficiency without complicating the overall device architecture
Solution Approach 2:
The patent modifies molecular parameters such as ligand geometry, metal center coordination, and aspect ratio to control emitter orientation. By changing these molecular parameters, the patent achieves enhanced external quantum efficiency while maintaining device structure simplicity
2Adaptability or versatility
If phosphorescent emitters with random orientation are used, then the material selection is flexible, but light extraction efficiency is reduced
Solution Approach 1:
The patent introduces local anisotropy in the emitter molecules through specific ligand designs (e.g., elongated ligands with different electron densities) that create localized charge asymmetry. This local quality difference drives preferential orientation of the emitters in the film, enhancing light extraction while maintaining material selection flexibility
Solution Approach 2:
The patent uses composite host-guest systems where the host matrix and guest emitter are specifically designed to work together. The host provides a environment that promotes orientational ordering of the anisotropic guest molecules, achieving both orientation control and efficient light extraction
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
Enhances the external quantum efficiency (EQE) of OLEDs by optimizing emitter orientation, leading to improved light output and device performance.
Implementation Method 1
Incorporation of organometallic complexes with a large aspect ratio in one direction, such as Ir, Os, Rh, Ru, Re, Pt, or Pd compounds with bis- or tris-heteroleptic ligands
Data Source
AI summary
New organometallic complexes having bis- or tris-heteroleptic ligands and large aspect ratio in one direction and their use in OLEDs to enhance the efficiency is disclosed. Such compounds can have a structure of Formula III,where rings A, B, C, and D are ring; L1 and L3 each a direct bond or a linking group; n1 and n2 are 0 or 1; if n1 or n2 is 1, then L2 or L4 is a direct bond or a linking group, and if n1 or n2 is 0, L2 or L4 is not present; Q1, Q2, Q3 and Q4 are a direct bond or oxygen; ring A is trans to ring D, ring B is trans to ring C in a square-planar coordination configuration; M2 is Pt, and the compound comprises at least one Pt-carbene bond.