Reflective Layer in OLED Display Device for Light Extraction
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Solution Overview
Problem
The formation accuracy of thin films in OLED display devices is degraded due to processing inaccuracies and deformation of fine masks, leading to performance issues, particularly with the end surfaces of organic layers not being formed at desired positions when multiple functional layers are stacked.
Innovation Solution
A display device configuration with a substrate, lower and upper electrodes, and a reflective layer between them, where the organic layers include light emitting layers and carrier adjustment layers, and the reflective layer is positioned to cover the end surfaces of the organic layers, enhancing light extraction and suppressing unwanted emission and current leakage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If mask deposition is used to form organic layers with multiple functional layers, then the display device can achieve practical use with OLEDs, but the formation accuracy of thin films is degraded due to processing inaccuracies and deformation of fine masks
Solution Approach 1:
A reflective layer is introduced as an intermediary component between the organic layer and the upper electrode. This reflective layer serves as a mediator that addresses the positioning inaccuracies of the organic layer end surfaces by providing a dedicated light reflection function, thereby compensating for the manufacturing precision degradation caused by mask deposition limitations
Solution Approach 2:
The patent segments the light emission function into two distinct components: the organic layer responsible for light generation and the reflective layer responsible for light reflection. This segmentation allows each layer to be optimized independently, where the reflective layer can precisely control light extraction without being constrained by the positioning accuracy limitations of the organic layer formed through mask deposition
2Ease of manufacture
If a fine mask with apertures corresponding to respective pixels is applied, then organic layers can be formed, but deformation of the aperture shape occurs leading to degraded formation accuracy
Solution Approach 1:
The reflective layer acts as an intermediary that compensates for aperture deformation effects. By providing a separate, precisely positioned reflective structure, it mediates between the deformed organic layer pattern and the desired light emission pattern, ensuring accurate light extraction even when the organic layer apertures are distorted
Solution Approach 2:
The patent addresses the two-dimensional aperture deformation problem by introducing a third dimension - the reflective layer positioned at a different vertical level. This dimensional transition allows the reflective layer to provide precise light reflection control independent of the horizontal plane deformation that occurs during mask deposition
3Reliability
If the end surface of the organic layer is not formed at a desired position, then performance of display elements degrades, but adding a reflective layer increases device complexity
Solution Approach 1:
The reflective layer is designed to perform multiple functions simultaneously: it reflects light to improve extraction efficiency, defines the light emission pattern, and compensates for positioning inaccuracies of the organic layer. This multi-functionality justifies the additional structural element by delivering multiple performance benefits from a single added component
Solution Approach 2:
The reflective layer is strategically positioned only where needed - at the end surface region of the organic layer - rather than uniformly throughout the entire device structure. This localized placement addresses the specific positioning accuracy problem at the critical end surface region while minimizing overall device complexity
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 luminance and color purity by ensuring the light emitted is of a predetermined wavelength, while preventing degradation in display performance and current leakage, resulting in a display device with desirable quality.
Implementation Method 1
a reflective layer arranged between the first upper electrode and the second upper electrode
Implementation Method 2
display devices with organic light-emitting diodes (OLEDs) applied thereto as display elements
Implementation Method 3
Such an organic layer is formed by, for example, vacuum vapor deposition
Data Source
AI summary
According to one embodiment, a display device includes a substrate, a first lower electrode and a second lower electrode arranged on the substrate, a first organic layer including a light emitting layer and arranged on the first lower electrode, a second organic layer including a light emitting layer and arranged on the second lower electrode, a first upper electrode arranged on the first organic layer, a second upper electrode arranged on the second organic layer and separated from the first upper electrode, and a reflective layer arranged between the first upper electrode and the second upper electrode.