Stacked OLED Emitter Structure for Charge-Balanced White Light
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Solution Overview
Problem
Existing organic light emitting diode (OLED) devices struggle to achieve balanced charge mobility between hole and electron mobilities in a red/green simultaneous light emitter, leading to difficulties in producing white light with high color purity and wide color gamut.
Innovation Solution
The OLED device incorporates a stacked structure with a red light emitter and a green light emitter, where the green light emitter is positioned closer to the cathode, using specific red and green host compounds and phosphorescence dopants to balance charge mobilities, and employs a charge generating layer to enhance emission efficiency and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a red/green simultaneous light emitter is used in OLED devices, then white light emission is achieved, but unbalanced charge mobility between hole and electron mobilities occurs
Solution Approach 1:
The light emitting layer is segmented into distinct red light emitter and green light emitter layers, with each layer having optimized charge transport properties. This segmentation allows independent optimization of hole and electron mobility in different regions, achieving overall charge balance while maintaining white light emission.
Solution Approach 2:
Different materials and compositions are used in different regions of the light emitting layer. The red light emitter region uses materials optimized for hole transport, while the green light emitter region uses materials optimized for electron transport, creating local quality variations that achieve global charge mobility balance.
2Device complexity
If conventional organic layers are used, then device structure is simple, but color purity and color gamut are insufficient
Solution Approach 1:
The patent employs composite organic materials with specific molecular structures and compositions in the light emitting layer. These composite materials enable precise control over emission spectra, achieving high color purity and wide color gamut while maintaining a relatively simple overall device structure.
Solution Approach 2:
The invention transitions from conventional single-layer emission to a vertically stacked multi-layer emission structure. This dimensional organization of different emitter layers enables independent optimization of color emission from each layer, achieving superior color purity and gamut.
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 enables the production of white light with improved color purity and wide color gamut by balancing hole and electron mobilities, resulting in optimal color coordinates and enhanced performance.
Implementation Method 1
The red light emitter may comprise a red host compound represented by the following Chemical Formula 1, and a red phosphorescence light emitting dopant. The green light emitter may comprise a green host compound and a green phosphorescence light emitting dopant.
Data Source
AI summary
Disclosed herein is an organic light emitting diode device. The organic light emitting diode device includes an anode, a cathode and a light emitting layer. The light emitting layer has a structure where a blue light emitter and a red/green simultaneous light emitter are stacked. The red/green simultaneous light emitter has a structure where a red light emitter and a green light emitter are stacked. The red light emitter includes a red host compound, and in some embodiments, the red host compound includes a spirobisfluorene-based compound where an aryl amino group is substituted. The green light emitter includes a green host compound, and the green host compound includes a mixture of a first green host compound and a second green host compound. In some embodiments, the first green host compound includes a biscarbazole-based compound and the second green host compound includes an indolocarbazole-based compound.