Organic Light-Emitting Device Charge Generation Layers
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Solution Overview
Problem
Existing organic light-emitting devices face challenges in achieving low driving voltage, high luminescent efficiency, and long lifespan due to limitations in charge generation and transport layers, particularly with amino group-containing compounds and inadequate energy level alignment.
Innovation Solution
The organic light-emitting device incorporates multiple emission units with charge generation layers, including n-type layers with metal-containing compounds and amino group-free p-type layers, along with hole and electron transport auxiliary layers, to facilitate efficient charge injection and transport, optimizing energy levels and device stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If amino group-containing compounds are used in charge generation layers, then charge injection is facilitated, but device lifespan is reduced due to instability
Solution Approach 1:
The patent extracts and removes amino groups from the charge generation layer compounds. The p-type charge generation layer uses compounds without amino groups (such as triphenylene derivatives), eliminating the source of instability while maintaining charge generation capability through alternative molecular structures with appropriate HOMO levels.
Solution Approach 2:
The patent changes the chemical composition parameters of the charge generation layers. Specifically, it transitions from amino group-containing compounds to amino group-free compounds, altering the molecular structure to improve stability. This parameter change maintains electrical functionality while eliminating degradation pathways associated with amino groups.
2Illumination intensity
If multiple emission units are stacked to achieve full-color emission, then color quality is improved, but device complexity increases
Solution Approach 1:
The patent divides the emission function into multiple independent emission units stacked in sequence, with each unit responsible for a specific color wavelength range. The device includes a first emission unit for blue light, a second emission unit for green light, and a third emission unit for red light, allowing full-color display through spatial segmentation of emission functions.
Solution Approach 2:
The patent implements multi-functional charge generation layers that serve multiple purposes: the p-type charge generation layer provides both hole injection and acts as a hole transport auxiliary layer, while the n-type charge generation layer provides electron injection and serves as an electron transport auxiliary layer. This multi-functionality reduces the need for separate auxiliary layers, simplifying the overall device structure despite multiple emission units.
3Productivity
If conventional charge generation layers are used, then device structure is simple, but luminescent efficiency is insufficient
Solution Approach 1:
The patent employs composite charge generation layer structures consisting of p-type and n-type charge generation layers with different material compositions. The p-type layer uses compounds like triphenylene derivatives with specific HOMO levels, while the n-type layer uses compounds with appropriate LUMO levels. This composite structure optimizes charge generation and transport properties, significantly improving luminescent efficiency compared to conventional single-layer structures.
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 configuration results in an organic light-emitting device with improved luminescent efficiency, extended lifespan, and reduced driving voltage by enhancing charge injection and transport processes.
Implementation Method 1
Carriers, such as holes and electrons, recombine in the emission layer to produce excitons. These excitons transit from an excited state to a ground state, thereby generating light.
Data Source
AI summary
An organic light-emitting device including a first electrode; a second electrode; emission units stacked between the first electrode and the second electrode and including at least one emission layer; and charge generation layers between two adjacent emission units, the charge generation layers each including an n-type charge generation layer and p-type charge generation layer, a maximum emission wavelength of light emitted by at least one of the emission units is different from that of another emission unit, one n-type charge generation layer includes a first compound and a metal-containing material, the first compound being represented by Formula 1, the p-type charge generation layers include an amino group-free compound, at least one of the emission units further includes a hole transporting (HT)-emission auxiliary layer on a first electrode side thereof, and the HT-emission auxiliary layer includes at least one second compound, the second compound being represented by Formula 2: