Organic Light Emitting Display Dual-Layer Doping Structure
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Solution Overview
Problem
Conventional organic light emitting displays suffer from deteriorated color reliability and lifespan due to non-uniform doping in the light emitting layer, leading to mixed color appearance at different viewing angles.
Innovation Solution
The organic light emitting display incorporates a first light emitting layer with a host and dopant, and a second light emitting layer formed between the electron-transporting and hole-transporting layers, with the second layer comprising only the light emitting dopant, optimizing the thickness and composition to inhibit host light emission and enhance luminous efficacy and lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If the light emitting layer is formed by co-depositing a host with a dopant, then the light emitting layer can be formed, but non-uniform doping occurs causing color reliability deterioration and lifespan reduction
Solution Approach 1:
The light emitting layer is divided into two separate layers: a first light emitting layer containing the host material and a second light emitting layer containing only the dopant. This segmentation prevents non-uniform doping by eliminating the co-deposition process, ensuring each layer has uniform composition and distinct functions.
2Ease of manufacture
If the light emitting layer is non-uniformly doped, then manufacturing is simpler, but mixed color appearance occurs at different viewing angles
Solution Approach 1:
By separating the host and dopant into different layers, the patent achieves uniform doping distribution within each layer while maintaining simple manufacturing processes. The first layer provides uniform host material and the second layer provides uniform dopant distribution, eliminating mixed color appearance at different viewing angles.
3Device complexity
If a single light emitting layer with host and dopant is used, then the structure is simpler, but host light emission causes viewing angle and lifespan deterioration
Solution Approach 1:
The patent divides the light emitting layer into two functional layers: the first light emitting layer with host material that receives charge carriers, and the second light emitting layer with dopant that emits light. This segmentation prevents host light emission by ensuring dopant-dominated emission, improving viewing angle and lifespan while maintaining reasonable structural complexity.
Solution Approach 2:
Each layer is designed with specific local properties: the first layer is optimized for charge carrier injection and transport with host material, while the second layer is optimized for light emission with dopant material. This local quality differentiation ensures that light emission occurs primarily from the dopant in the second layer, eliminating the viewing angle and lifespan issues caused by host emission.
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 color reliability across viewing angles and extends the lifespan of the display by ensuring consistent light emission and reducing color mixing, as evident in the comparative examples.
Implementation Method 1
Holes injected from the anode recombine with electrons injected from the cathode in the light emitting layer to form electron-hole pairs, i.e., excitons. Upon an exciton's transition to a ground state, energy is released. Based on this energy, the organic light emitting display emits light.
Data Source
AI summary
An organic light emitting display includes a red light emitting layer, a green light emitting layer and a blue light emitting layer formed between first and second electrodes, a hole-transporting layer formed between the first electrode and each of the red, the green and the blue light emitting layers, and an electron-transporting layer formed between the second electrode and each of the red, the green and the blue light emitting layers, wherein at least one light emitting layer of the red, the green and the blue light emitting layers includes a first light emitting layer including a light emitting host and a light emitting dopant, and a second light emitting layer which is formed between the first light emitting layer and at least one of the electron-transporting layer and the hole-transporting layer, and includes the light emitting dopant.