Tandem Light-Emitting Device with Segmented Host-Dopant Layers
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Solution Overview
Problem
Current organic light-emitting devices face challenges in achieving high luminous efficiency and extended device lifetime due to limitations in the structure and materials used in their light-emitting layers, particularly in tandem structures where roll-off phenomena affect performance at higher luminance levels.
Innovation Solution
A light-emitting device is designed with a tandem structure incorporating a first and second light-emitting layer emitting different wavelengths, each comprising a host and dopant with specific energy level differences, and a charge generation layer, which includes p-type and n-type charge generation layers doped with p-dopants and n-dopants, to enhance charge balance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a tandem structure with multiple light-emitting layers is used, then luminous efficiency is improved, but device complexity increases
Solution Approach 1:
The light-emitting device is divided into multiple independent light-emitting layers (first light-emitting layer and second light-emitting layer), each capable of emitting light at different wavelengths. This segmentation allows each layer to be optimized independently for specific wavelength emission, improving overall luminous efficiency while maintaining manageable complexity through modular design
Solution Approach 2:
The tandem structure incorporates multiple light-emitting layers that can emit different wavelengths of light simultaneously, enabling the device to perform multiple functions (emitting different colors) within a single integrated structure. This multi-functionality approach improves luminous efficiency by utilizing different energy levels without requiring separate devices
2Productivity
If host and dopant materials with specific energy level differences are used, then luminous efficiency is improved, but manufacturing precision requirements increase
Solution Approach 1:
The patent specifies precise energy level parameters for host and dopant materials, with the energy level difference controlled within 0.1-0.3 eV. By establishing clear parameter ranges and selection criteria, the invention transforms the manufacturing challenge into a standardized material selection process, improving luminous efficiency through optimized energy transfer while providing guidance for consistent manufacturing
Solution Approach 2:
Different host and dopant material combinations are used in different light-emitting layers to optimize for specific wavelength emissions. The first light-emitting layer uses materials optimized for its target wavelength, while the second light-emitting layer uses different materials optimized for its wavelength, allowing each region to have the specific quality needed for its function
3Duration of action of stationary object
If charge generation layers with p-type and n-type doping are incorporated, then device lifetime is extended, but device complexity increases
Solution Approach 1:
Charge generation layers with p-type and n-type doping are introduced as intermediary layers between the light-emitting layers and the electrodes. These intermediary layers facilitate efficient charge generation and transport, preventing charge accumulation that would otherwise degrade the device. The p-type and n-type dopants act as mediators to balance charge carriers, extending device lifetime while adding a manageable layer of complexity
Solution Approach 2:
The charge generation layers are positioned strategically within the device structure to preemptively generate and balance charge carriers before they can cause degradation. By incorporating p-type and n-type doping in advance, the device prevents future charge imbalance issues, extending operational lifetime while maintaining a structured approach to complexity management
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 improves luminous efficiency and extends device lifetime by preventing roll-off and maintaining efficiency across varying luminance levels, as demonstrated by comparative evaluation results showing reduced driving voltage and increased efficiency and lifespan.
Implementation Method 1
a first light-emitting layer disposed on the hole transport region and emitting light of a first wavelength, a second light-emitting layer disposed on the hole transport region and emitting light of a second wavelength different from the first wavelength
Implementation Method 2
a charge generation layer disposed between the first light-emitting layer and the second light-emitting layer... a p-type charge generation layer doped with p-dopants, and an n-type charge generation layer doped with n-dopants
Data Source
AI summary
A light-emitting device including a first electrode, a hole transport region disposed on the first electrode, a first light-emitting layer disposed on the hole transport region and emitting light of a first wavelength, a second light-emitting layer disposed on the hole transport region and emitting light of a second wavelength different from the first wavelength, an electron transport region disposed on the first light-emitting layer and the second light-emitting layer, and a second electrode disposed on the electron transport region, wherein the second light-emitting layer includes a first sub light-emitting layer including a first host and a first dopant and emitting the light of the second wavelength, and a second sub light-emitting layer including a second host different from the first host and a second dopant and emitting the light of the second wavelength. Accordingly, a luminous efficiency and device lifetime of the light-emitting device may be improved.