OLED Green Sub-Pixel Host-Dopant Segmentation
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Solution Overview
Problem
Organic light emitting display devices face issues with light efficiency and emission region shift due to inefficient recombination of electrons and holes in the organic emission layer, leading to energy loss and faults like light leakage.
Innovation Solution
The formation of separately stacked hole host layers and dopant layers in red, green, and blue sub-pixel regions enhances light efficiency by optimizing the recombination process and reducing energy loss, with specific layer structures and materials used for each color to improve exciton confinement and emission characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional organic emission layer with mixed host and dopant materials is used, then the device structure remains simple, but light efficiency is low and emission region shift faults occur due to inefficient electron-hole recombination
Solution Approach 1:
The organic emission layer is segmented into multiple sub-layers: a first hole host layer adjacent to the hole transport layer, a dopant host layer containing phosphorescent dopant, and a second hole host layer adjacent to the electron transport layer. This segmentation separates the functions of hole transport, phosphorescence emission, and electron transport, enabling efficient electron-hole recombination while preventing emission region shift and light leakage.
2Reliability
If the triplet potential energy of the emission layer is higher than the electron transport layer, then electron injection is facilitated, but energy loss occurs and current efficiency reduces at high temperatures
Solution Approach 1:
The patent optimizes the triplet potential energy parameters of different layers. The first hole host layer has triplet potential energy higher than the electron transport layer to facilitate electron injection, while the second hole host layer has triplet potential energy lower than the electron transport layer to prevent energy loss and improve high-temperature reliability. This parameter optimization balances injection efficiency with energy conservation.
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 increases light efficiency and prevents emission region shift faults, resulting in improved current efficiency and reduced reliability issues at high temperatures, as demonstrated by enhanced performance in green sub-pixel regions and extended to red and blue sub-pixels.
Implementation Method 1
The organic light emitting diode generates excitons by injecting electrons and holes into the emission layer through an electron injection electrode (i.e., a cathode) and a hole injection electrode (i.e., an anode) and recombining the electrons and the holes within the emission layer. Also, the organic light emitting diode emits light when the excitons are transitioned from an excited state into a ground state.
Data Source
AI summary
An organic light emitting display device including a first electrode defined into red, green and blue sub-pixel regions; a hole injection layer disposed on the first electrode; a first hole transport layer disposed on the hole injection layer; first, second and third organic emission layers arranged on the first hole transport layer opposite to the respective red, green and blue sub-pixel regions; an electron transport layer disposed on the first, second and third organic emission layers; and a second electrode disposed on the electron transport layer. The second organic emission layer opposite to the green sub-pixel region is formed in a stacked structure including first and second hole host layers and a dopant host layer.