OLED Emissive Material Composition for Single-Source Co-Evaporation
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Solution Overview
Problem
Current OLED devices require multiple evaporation sources for complex emitter systems, making the fabrication process complicated and costly, and achieving stable co-evaporation of materials with different evaporation temperatures is challenging.
Innovation Solution
A novel composition of a first compound and a second compound with different chemical structures, having evaporation temperatures within 150 to 350°C and a controlled concentration ratio, is used to form a stable delayed fluorescent emitter system, allowing for co-evaporation from a single sublimation crucible in a vacuum thermal evaporation process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple evaporation sources are used for complex emitter systems, then the emission performance can be achieved, but the fabrication process becomes complicated and costly
Solution Approach 1:
The patent combines multiple emitter materials (host and guest compounds) into a single premixed emitter composition that can be deposited from one evaporation source. This merging approach maintains the complex emission performance needed for saturated colors while simplifying the fabrication process to use fewer evaporation sources, directly resolving the contradiction between performance and complexity
2Manufacturing precision
If materials with different evaporation temperatures are co-evaporated, then the desired composition can be achieved, but stable co-evaporation is challenging
Solution Approach 1:
The patent selects host and guest compounds whose evaporation temperatures differ by less than 50°C, optimizing the thermal parameters for stable co-evaporation. This parameter control ensures that both materials evaporate simultaneously at consistent rates from a single source, achieving precise composition control while maintaining evaporation stability
3Ease of manufacture
If a single sublimation crucible is used for co-evaporation, then the fabrication process is simplified, but achieving stable evaporation of mixed materials is difficult
Solution Approach 1:
The patent creates a homogeneous premixed emitter composition where host and guest compounds are thoroughly mixed at the molecular level before deposition. This homogeneity ensures uniform evaporation behavior from the single sublimation crucible, maintaining stable deposition while keeping the fabrication process simple and equipment requirements minimal
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
This approach simplifies the fabrication process by reducing the number of evaporation sources and ensures a stable composition, enhancing the internal quantum efficiency of OLEDs beyond the spin statistics limit through delayed fluorescence.
Implementation Method 1
co-evaporated from one sublimation crucible in a vacuum thermal evaporation (VTE) process
Implementation Method 2
evaporation from a single sublimation crucible
Implementation Method 3
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
A composition formed of a mixture of two compounds having similar thermal evaporation properties that are pre-mixed into an evaporation source that can be used to co-evaporate the two compounds into an emission layer in OLEDs via vacuum thermal evaporation process is disclosed. The first and second compounds can have an evaporation temperature T1 and T2, respectively, of 150 to 350° C., and the absolute value of T1-T2 can be less than 20° C. The first compound can have a concentration C1 in the mixture and a concentration C2 in a film formed by evaporating the mixture in a vacuum deposition tool at a constant pressure between 1×10−6 Torr to 1×10−9 Torr, at a 2 Å/sec deposition rate on a surface positioned at a predefined distance away from the mixture being evaporated, where the absolute value of (C1−C2)/C1 is less than 5%.