OLED Organometallic Complexes With Horizontal Emission Orientation
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Solution Overview
Problem
Conventional OLEDs face challenges in achieving high efficiency and maximizing light extraction due to the orientation of emissive molecules, which limits their performance in applications such as displays and lighting.
Innovation Solution
Incorporation of organometallic complexes with a large aspect ratio in one direction, such as Ir, Os, Rh, Ru, Re, Pt, or Pd-based 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
1Illumination intensity
If conventional OLED materials are used, then the device structure is simple, but the light extraction efficiency is limited due to random molecular orientation
Solution Approach 1:
The patent applies asymmetry by designing organometallic complexes with large aspect ratios (length-to-width ratio greater than 1.5:1), where the asymmetric molecular geometry inherently promotes horizontal orientation of the emission dipole moment parallel to the substrate surface, thereby improving light extraction efficiency without requiring additional structural modifications to the OLED device
Solution Approach 2:
The patent changes the molecular geometry parameter (aspect ratio) of the organometallic complex from conventional near-spherical shapes to elongated structures with specific dimensional ratios, which fundamentally alters the orientation behavior of the emission dipole and enhances the external quantum efficiency of the OLED
2Illumination intensity
If molecules are oriented vertically, then the molecular packing is dense, but the light extraction efficiency decreases due to reduced surface area facing the light-emitting façade
Solution Approach 1:
The asymmetric, elongated molecular structure with large aspect ratio creates an inherent geometric preference for horizontal alignment, maximizing the projected surface area of the emission dipole toward the light-extraction interface while maintaining efficient molecular packing through controlled intermolecular interactions
3Productivity
If random molecular orientation is present, then the fabrication process is simple, but the emission efficiency is limited
Solution Approach 1:
The organometallic complexes with large aspect ratios exhibit self-organizing behavior during the OLED fabrication process, where the asymmetric molecular geometry automatically directs the emission dipole orientation horizontally without requiring external alignment fields or complex multi-step orientation control procedures, thereby achieving high emission efficiency through self-service molecular organization
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 external quantum efficiency (EQE) of OLEDs by ensuring horizontal orientation of emissive molecules, thereby improving light extraction and overall device performance.
Implementation Method 1
Organic light emitting diodes/devices (OLEDs)... OLEDs make use of thin organic films that emit light when voltage is applied across the device
Implementation Method 2
Organic electroluminescent materials and devices... OLEDs make use of thin organic films that emit light when voltage is applied across the device
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.