Sub-Pixel Trench Electrode Layout for Uniform OLED Emission
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Solution Overview
Problem
Existing display devices have low aperture ratio and luminance due to a limited light-emitting area and the coffee ring effect, resulting in a dark display screen.
Innovation Solution
A display device with sub-pixels featuring a thin-film-transistor layer, planarization film with trenches, and light-emitting elements, where the lower electrode is shaped as an island and positioned inside the trench to prevent short circuits and enhance light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an insulating layer (bank) is formed to cover the edge of the lower electrode to prevent short circuit, then short circuit prevention is improved, but the light-emitting area is reduced resulting in low aperture ratio
Solution Approach 1:
The patent transitions from a 2D planar insulating layer to a 3D protruding structure (bank with height of 1-10 μm) that extends vertically. This dimensional change allows the insulating function to be achieved through vertical protrusion rather than horizontal coverage, thereby preventing short circuits while maintaining a larger light-emitting area and improving aperture ratio.
Solution Approach 2:
The bank structure is formed in advance before the light-emitting layer is deposited. This preliminary formation of the protruding insulating structure ensures that the lower electrode edge is protected from short circuiting with the upper electrode before the light-emitting materials are applied, while the light-emitting layer is subsequently formed only in the opening portions of the bank.
2Reliability
If the light-emitting material is coated only in the opening portion of the insulating layer, then short circuit prevention is improved, but the light emission uniformity deteriorates due to coffee ring effect
Solution Approach 1:
By giving the insulating layer a vertical dimension (protruding structure with height 1-10 μm), the patent creates a three-dimensional configuration where the light-emitting layer can be uniformly distributed on the horizontal surface of the bank's opening portion, preventing the coffee ring effect that occurs in flat 2D configurations.
Solution Approach 2:
The bank structure creates different local regions: the protruding sides provide insulation and structural support, while the horizontal top surface of the opening portion provides a uniform substrate for light-emitting material deposition. This local differentiation allows uniform light emission while maintaining electrical insulation.
3Reliability
If the light-emitting layer is formed only in the opening portion of the insulating layer, then short circuit prevention is improved, but the aperture ratio is reduced resulting in dark display screen
Solution Approach 1:
The patent uses vertical protrusion (1-10 μm height) of the insulating bank to achieve electrical isolation, which allows the light-emitting area to extend closer to the electrode edges without causing short circuits. This dimensional approach increases the effective aperture ratio compared to planar insulating structures.
Solution Approach 2:
The protruding bank structure is formed beforehand to define the light-emitting region boundaries. This preliminary 3D structure allows maximum light-emitting area to be utilized while ensuring electrical isolation is already in place before light-emitting layer deposition.
Data Source
AI summary
A display device includes a plurality of sub-pixels, a support body, a thin-film-transistor layer, a light-emitting-element layer, and a sealing layer. The thin-film-transistor layer includes a plurality of thin-film transistors and a planarization film. The light-emitting-element layer includes a plurality of light-emitting elements. Each of the plurality of light-emitting elements includes a lower electrode, a functional layer, and an upper electrode. The lower electrode is a sub-pixel electrode shaped into an island and provided for each of the sup-pixel electrodes. The upper electrode is a common electrode formed in common among all the plurality of sub-pixels. The planarization film includes a trench shaped into a frame and provided for each of the sub-pixels. The trench defines a light-emitting region of the light-emitting element for each of the sub-pixels.