Bottom-Emitting OLED Reflective Structure for Light Extraction
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Solution Overview
Problem
Top-emitting OLED devices face challenges in mass production due to stringent requirements for layer thicknesses, high sheet resistance, and microcavity effects, leading to uneven light emission and reduced light transmittance, while bottom-emitting structures are preferred for simplicity and ease of production.
Innovation Solution
A bottom-emitting OLED display panel design featuring a reflective structure between the protective layer and planarization layer, which reflects light emitted from the OLED device and covers the region occupied by the driving transistor, increasing the light emitting area and light extracting rate, and utilizing a reflective layer with a specific geometry and material composition to enhance reflectivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a bottom-emitting OLED structure is used, then the manufacturing process is simplified and mass production is easier, but the light emitting area is reduced due to the driving transistor occupying space
Solution Approach 1:
The reflective structure extends vertically between the protective layer and planarization layer, utilizing the third dimension (height) to redirect light paths. This allows light to be reflected from the substrate side back through the OLED layers, effectively increasing the light emitting area without requiring additional planar space that would compromise the driving transistor region.
Solution Approach 2:
The reflective structure acts as an intermediary element that intercepts light emitted from the OLED device and redirects it toward regions occupied by the driving transistor. This mediator component enables light to reach areas that would otherwise be blocked, effectively increasing the functional light emitting area without complicating the bottom-emitting manufacturing process.
2Illumination intensity
If light is emitted from the substrate side, then the anode layer can use high work function materials with high light transmittance, but the light path is blocked by the driving transistor region
Solution Approach 1:
The reflective structure creates optical path folding through reflection, similar to how mechanical systems use mirrors to redirect energy paths. This allows light to bounce off the reflective structure and reach areas blocked by the driving transistor, effectively extending the light emitting area while maintaining high light transmittance through the anode layer.
Solution Approach 2:
The reflective structure converts what would be wasted light (blocked by the driving transistor region) into useful light output by reflecting it toward active display areas. This transforms the harmful blocking effect of the driving transistor into a beneficial light redirection mechanism that increases overall light emitting area.
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
The design increases the light emitting area and light extracting rate of the OLED device, improving the lifetime of the light emitting material and reducing the impact of photogenerated leakage current, thereby enhancing display performance.
Implementation Method 1
a reflective structure disposed between the protective layer and the planarization layer, the reflective structure is configured for reflecting light emitted from the OLED device and radiated on the reflective structure
Data Source
AI summary
A bottom-emitting OLED display panel is provided. The bottom-emitting OLED display panel includes: a driving transistor disposed on a substrate; a protective layer covering the driving transistor; a planarization layer disposed on the protective layer; and a OLED device disposed on the planarization layer; and a reflective structure disposed between the protective layer and the planarization layer, the reflective structure is configured for reflecting light emitted from the OLED device and radiated on the reflective structure; a bottom surface of the reflective structure which is close to the protective layer at least covers a region occupied by the driving transistor.