OLED Functional Layer Thickness Profiles for Uniform Emission
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Solution Overview
Problem
The manufacturing of light-emitting elements in electronic devices, such as TVs and smartphones, faces challenges in achieving uniform light-emitting characteristics due to non-uniform film properties caused by differences in thickness between the center and edge portions of the coating layer, leading to inefficiencies in light-emitting area and performance.
Innovation Solution
The electronic device incorporates a specific structure with a base layer, a first electrode, a pixel defining layer, a hole transport region with a thickness decreasing from the center to the edge, an emission layer with a thickness increasing from the center to the edge, an electron transport region, and a second electrode, where the hole transport region and emission layer are formed using inkjet printing and deposition methods respectively, to enhance light-emitting uniformity and area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a coating method such as inkjet printing is used to manufacture light-emitting elements, then manufacturing flexibility and area coverage are improved, but film thickness uniformity deteriorates due to differences between center and edge portions
Solution Approach 1:
The patent applies local quality by creating different thickness profiles in different regions of the functional layers. Specifically, the hole transport layer has a first thickness at the center and a second thickness at the edge, while the emission layer has a third thickness at the center and a fourth thickness at the edge, with the center thickness greater than edge thickness. This localized thickness variation compensates for the non-uniformity inherent in inkjet printing, improving overall film uniformity while maintaining manufacturing flexibility.
2Productivity
If the light-emitting area is increased to improve device performance, then output and efficiency are improved, but light-emitting uniformity deteriorates due to non-uniform film properties
Solution Approach 1:
The patent implements local quality by establishing specific thickness relationships in different regions: the hole transport layer thickness decreases from center to edge (first thickness > second thickness), and the emission layer thickness decreases from center to edge (third thickness > fourth thickness). This gradient structure ensures that even when the light-emitting area is increased, the light-emitting uniformity is maintained because each region has optimized thickness for its position, compensating for the non-uniform deposition characteristics.
3Device complexity
If functional layers are deposited with uniform thickness to simplify manufacturing, then manufacturing complexity is reduced, but light-emitting uniformity deteriorates due to inherent coating non-uniformity
Solution Approach 1:
The patent applies parameter changes by deliberately varying the thickness parameter of functional layers across different spatial positions. Instead of maintaining constant thickness, the hole transport layer and emission layer are designed with thickness gradients (center thicker than edge). This parameter variation compensates for the non-uniformity introduced by inkjet printing, achieving improved light-emitting uniformity without significantly increasing manufacturing complexity, as the thickness control can be integrated into the existing deposition process.
Data Source
AI summary
An electronic device includes a base layer, a first electrode disposed on the base layer, a pixel defining layer disposed on the base layer and having an opening that exposes an upper surface of the first electrode, a hole transport region disposed in the opening and having a thickness that gradually decreases from a center of the opening toward a side surface of the pixel defining layer, an emission layer disposed on the hole transport region and having a thickness that gradually increases from the center of the opening toward the side surface of the pixel defining layer, an electron transport region disposed on the emission layer, and a second electrode disposed on the electron transport region. This electronic device may increase a light-emitting area exhibiting uniform (or substantially uniform) light-emitting characteristics and exhibit high light-emitting efficiency.