OLED Sub-Pixel HOMO Energy Alignment for Mass Production
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Solution Overview
Problem
The existing organic light-emitting display devices face challenges in achieving efficient light emission and long product lifetime due to the need for multiple deposition masks and sub-hole transport layers, which complicates mass production and increases yields loss, especially when dealing with different color light-emitting layers.
Innovation Solution
The proposed solution involves an organic light-emitting device structure where the thickness of different color light-emitting layers is varied to achieve optimal optical distances without an auxiliary hole transport layer, with specific highest occupied molecular orbital (HOMO) energy level differences between the light-emitting layers and a common layer, allowing for efficient light emission and extended product lifetime.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sub-hole transport layers with different thicknesses are applied to control emission positions for different color light-emitting layers, then light emission efficiency is improved, but device complexity and manufacturing difficulty increase due to requiring additional deposition masks
Solution Approach 1:
The invention extracts and removes the sub-hole transport layer from the device structure. Instead of using separate sub-hole transport layers with different thicknesses for each color, the patent achieves optimal emission positions by controlling only the thickness of the light-emitting layers themselves, thereby simplifying the overall structure and reducing manufacturing complexity while maintaining light emission efficiency
Solution Approach 2:
The invention makes the light-emitting layer perform multiple functions: it not only emits light of specific colors but also serves as the optical distance control element. By varying the thickness of the light-emitting layer, the patent simultaneously achieves both color emission and emission position control, eliminating the need for separate sub-hole transport layers
2Manufacturing precision
If multiple deposition masks are used to form sub-hole transport layers with different thicknesses for different sub-pixels, then emission position control is achieved, but productivity decreases due to increased yields loss
Solution Approach 1:
The light-emitting layer is designed to serve dual purposes: emitting light and controlling emission position through its thickness. This eliminates the need for multiple deposition masks for sub-hole transport layers, allowing all layers to be formed using standard deposition processes and significantly improving mass production efficiency
Solution Approach 2:
The invention changes the thickness parameter of the light-emitting layer to control emission position for different colors (blue, green, red). By adjusting this single parameter during the deposition process, the patent achieves precise emission position control without requiring multiple masks or complex patterning steps, thereby enhancing productivity
3Reliability
If the number of deposition masks is increased to realize optical distance adjustment with multiple stacks, then light emission efficiency is improved, but the number of masks and yields loss increase making mass production difficult
Solution Approach 1:
The invention removes the auxiliary hole transport layer from the structure. Instead of using multiple stacks with auxiliary transport layers, the patent achieves optimal emission efficiency by precisely controlling the thickness of the light-emitting layer and its energy level alignment with the common hole transport layer, thereby eliminating unnecessary layers and masks for mass production
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 enhances light emission efficiency and extends product lifetime by eliminating the need for additional masks and layers, facilitating mass production while maintaining color accuracy and emission quality.
Implementation Method 1
Holes and electrons from the anode and cathode are injected into the organic light-emitting layer, and are combined with each other in the organic light-emitting layer, thus generating excitons. When the generated excitons are changed from an excited state to a ground state, the organic light-emitting device emits light at the sub-pixels.
Data Source
AI summary
An organic light-emitting device, including: a substrate including a blue sub-pixel, a green sub-pixel, and a red sub-pixel, each blue sub-pixel, green sub-pixel, and red sub-pixel respectively including an anode, a first common layer, a second common layer, and a cathode, in the blue sub-pixel, a blue light-emitting layer between the first common layer and the second common layer, in the green sub-pixel, a green light-emitting layer between the first common layer and the second common layer, and in the red sub-pixel, a red light-emitting layer between the first common layer and the second common layer, wherein HOMO energy levels of the blue, green, and red light-emitting layers are each lower than a HOMO energy level of the first common layer, and wherein the HOMO energy level of the green light-emitting layer is 0.2 eV or more higher than the HOMO energy level of the blue light-emitting layer.