OLED Cathode 2D Lattice Structure for Plasmon Extraction
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Solution Overview
Problem
The existing organic light emitting diodes (OLEDs) face challenges in achieving high light extraction efficiency, particularly for cathode top emission-type OLEDs, where the relationship between the pitch of periodic fine uneven structures and extraction wavelengths is unknown, leading to inefficient light extraction and brightness issues in display and illumination devices.
Innovation Solution
A top emission-type OLED with a two-dimensional lattice structure formed on the semi-transmissive metal layer, where the center-to-center distance of convex or concave portions is within a specific range, allowing for efficient extraction of surface plasmons as light, and a random fine uneven structure on the cathode surface to enhance light extraction efficiency across a broad wavelength range from visible light to near infrared.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a periodic fine uneven structure is formed on the cathode surface to extract surface plasmons as light, then light extraction efficiency is improved, but the relationship between pitch and extraction wavelength is unknown leading to wavelength deviation
Solution Approach 1:
The patent applies parameter changes by systematically varying the pitch of the periodic fine uneven structure to match different extraction wavelengths. By establishing the relationship P = λ/n (where P is pitch, λ is wavelength, and n is refractive index), the invention enables precise control of extracted light wavelength through pitch adjustment, resolving the wavelength deviation problem while maintaining high light extraction efficiency
Solution Approach 2:
The patent replaces the trial-and-error approach to optimizing uneven structure pitch with a theoretical calculation model based on electromagnetic wave theory. This substitution of mechanical/experimental optimization with theoretical calculation enables precise prediction of extraction wavelengths for given pitch values, eliminating wavelength control uncertainties
2Loss of energy
If the cathode metal layer is made thin to allow light transmission in top emission-type OLEDs, then light extraction is enabled, but structural strength and electrical conductivity are reduced
Solution Approach 1:
The patent applies local quality by creating periodic fine uneven structures on the cathode surface that concentrate light extraction functionality at specific locations (the uneven portions) while the rest of the thin cathode layer maintains its structural and electrical functions. This localized approach enables effective light extraction without requiring the entire cathode layer to be thick
Solution Approach 2:
The patent introduces a new dimension (surface topology) by forming periodic fine uneven structures on the cathode surface. This dimensional change from a flat thin layer to a structured surface enables enhanced light extraction through surface plasmon coupling while the overall cathode layer remains thin, preserving its structural and electrical properties
3Loss of energy
If a two-dimensional lattice structure with specific pitch is formed on the semi-transmissive metal layer, then surface plasmons are efficiently extracted as light, but manufacturing precision requirements increase
Solution Approach 1:
The patent applies preliminary action by providing a theoretical framework and calculation formulas before the manufacturing process. The relationship P = λ/n is established in advance, allowing manufacturers to calculate the required pitch for any desired wavelength before fabrication, thereby reducing manufacturing precision requirements through pre-planned design
Solution Approach 2:
The patent uses copying by creating periodic fine uneven structures that replicate a fundamental pattern across the cathode surface. This periodic replication of the basic uneven structure unit enables scalable manufacturing with relaxed precision requirements, as the same pattern can be copied across different areas rather than requiring unique precision control for each location
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 proposed solution achieves high light extraction efficiency with minimal risk of wavelength deviation, even with slight changes in the fine uneven structure, improving brightness and efficiency in OLEDs for both monochromatic and white light emission.
Implementation Method 1
a two-dimensional lattice structure, in which a plurality of convex portions are arrayed periodically and two-dimensionally, is formed on a surface of the semi-transmissive metal layer which is in contact with the transparent conductive layer side
Implementation Method 2
a two-dimensional lattice structure, in which a plurality of convex portions are arrayed periodically and two-dimensionally, is formed on a surface of the semi-transmissive metal layer
Implementation Method 3
an organic electro-luminescence layer including a light emitting layer containing an organic light emitting material
Data Source
AI summary
An organic light emitting diode, which is a top emission-type, is configured so that at least the following are laminated on the substrate: a reflective layer including a metal material; an anode conductive layer including a transparent conductive material; an organic EL layer having a light emitting layer which contains an organic light emitting material; and a cathode conductive layer in which a semi-transmissive metal layer and a transparent conductive layer including a transparent conductive material are laminated. On the surface of the semi-transmissive metal layer that is in contact with the transparent conducive layer side, a two-dimensional lattice structure is formed in which a plurality of protrusions are arranged periodically and two-dimensionally.