OLED Anode Undulating Arc Structure for Light Extraction
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Solution Overview
Problem
Conventional OLED devices suffer from low light efficiency due to total reflection at the interfaces, with only about 17% of light being emitted, as light passes from an optically denser medium to an optically thinner medium, resulting in significant light loss.
Innovation Solution
The use of a PEDOT:PSS thin film as an anode with a periodically undulating arc structure, formed through a wet coating and transfer-printing method, reduces the refractive index mismatch and avoids total reflection by changing the incident angles of emitted light, allowing more light to propagate out of the substrate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a conventional flat anode structure is used, then the device structure is simple, but total reflection occurs at the interfaces causing low light efficiency
Solution Approach 1:
The patent applies curvature by introducing periodic undulating arc structures on the surfaces of the anode, organic electroluminescent structure, and cathode. This curved surface design modifies the incident angles of emitted light, enabling light to escape the device more effectively by avoiding total internal reflection at the interfaces, thereby significantly improving light efficiency while maintaining manufacturing feasibility
Solution Approach 2:
The patent changes the geometric parameters of the device surfaces by introducing periodic undulating structures with specific amplitudes and wavelengths. This parameter modification alters the optical path and incident angles of light, transforming the optical characteristics at the interfaces to reduce total reflection and enhance light extraction efficiency
2Reliability
If an ITO thin film is used as the anode, then the electrical conductivity is good, but the production cost is high
Solution Approach 1:
The patent replaces the expensive ITO (indium tin oxide) material with PEDOT:PSS (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)), which is a cheaper organic conductive polymer. This material substitution significantly reduces production costs while maintaining adequate electrical conductivity for the anode function
Solution Approach 2:
The patent uses PEDOT:PSS as a composite organic material that combines conductive polymer (PEDOT) with sulfonate counterions (PSS). This composite structure provides both electrical conductivity and processability, enabling cost-effective manufacturing through solution-based deposition techniques
3Ease of manufacture
If a PEDOT:PSS thin film is used as the anode, then the production cost is reduced, but the light efficiency needs to be improved
Solution Approach 1:
The patent applies curvature by introducing periodic undulating arc structures on the surfaces of the anode, organic electroluminescent structure, and cathode. This curved surface design modifies the incident angles of emitted light, enabling light to escape the device more effectively by avoiding total internal reflection at the interfaces, thereby significantly improving light efficiency while maintaining manufacturing feasibility
Solution Approach 2:
The patent applies the undulating arc structure specifically at the interfaces where light extraction occurs (anode, organic electroluminescent structure, and cathode surfaces). This localized structural modification targets the critical regions for light emission, improving light efficiency without requiring changes to the entire device structure
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 increases the light efficiency of bottom-emitting type OLED devices by reducing total reflection and enhancing light emission, while also lowering production costs by replacing ITO with PEDOT:PSS thin films.
Implementation Method 1
a total reflection phenomenon is existed. A light having an incident angle greater than a critical angle cannot reach the glass substrate because of the total reflection phenomenon
Implementation Method 2
the light is propagated from an optically denser medium (with a higher refractive index) to an optically thinner medium (with a lower refractive index)
Data Source
AI summary
An organic electroluminescent device structure and manufacturing method for the same are provided. Surfaces of an anode, an organic electroluminescent structure and a cathode all have arc structures undulating periodically to avoid the total reflection in propagating an exit light to the substrate, increasing the light efficiency. Utilizing a PEDOT:PSS thin film as a material for the anode to replace an ITO material, the cost is reduced. The manufacturing method utilizes a wet coating process to form the PEDOT:PSS thin film as the anode so as to reduce the cost. Utilizing a transfer-printing method to pattern the PEDOT:PSS thin film to form an arc structure undulating periodically on the PEDOT:PSS thin film (the anode) to avoid the total reflection inside the organic electroluminescent device such that most light can be propagated out from the substrate. Accordingly, a light efficiency of the bottom-emitting type organic electroluminescent device is increased.