Organic EL Optical Resonator Preventing Short Circuits
Solution Overview
Problem
Existing organic electroluminescent devices face challenges in achieving high luminous efficiency while preventing short circuits between electrodes, particularly in top-emission structures, where thin organic layers are prone to short circuits due to surface unevenness and static electricity, and thickening the organic layer reduces luminous efficiency.
Innovation Solution
Incorporating a conductive light-reflecting layer between the first and second electrodes, which forms an optical resonator to enhance light emission and maintain a sufficient distance between electrodes to prevent short circuits, allowing for a thicker first carrier transporting layer without affecting the optical resonator's optical length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the organic layer is made thin to achieve high luminous efficiency through optical resonator enhancement, then the luminous efficiency is improved, but short circuits between electrodes occur due to surface unevenness
Solution Approach 1:
The patent divides the organic layer into multiple functional sub-layers: a first carrier transporting layer (10-50 nm) positioned away from the first electrode, a second carrier transporting layer (5-20 nm) positioned away from the second electrode, and an emitting layer in between. This segmentation allows the optical resonator to function with enhanced efficiency while maintaining sufficient distance from the electrodes to prevent short circuits caused by surface unevenness.
Solution Approach 2:
The patent introduces carrier transporting layers as intermediary substances between the electrodes and the optical resonator structure. These layers act as buffer zones that prevent direct contact between the electrodes while still allowing the optical resonator to enhance light emission, thus resolving the contradiction between achieving high luminous efficiency and preventing short circuits.
2Reliability
If the organic layer is thickened to prevent short circuits between electrodes, then short circuit prevention is improved, but luminous efficiency decreases due to reduced optical resonator effect
Solution Approach 1:
By segmenting the organic layer into distinct functional regions with optimized thicknesses, the patent achieves both sufficient overall thickness to prevent short circuits and localized thin regions that maintain strong optical resonator effects. The first carrier transporting layer (10-50 nm) and second carrier transporting layer (5-20 nm) are positioned to create appropriate spacing from electrodes while preserving optical resonance.
Solution Approach 2:
The patent applies different thickness specifications to different parts of the organic layer: the first carrier transporting layer is positioned 10-50 nm from the first electrode, the emitting layer has specific thickness optimized for emission, and the second carrier transporting layer is positioned 5-20 nm from the second electrode. This local optimization allows simultaneous achievement of short circuit prevention and high luminous efficiency.
3Reliability
If polishing is applied to smooth the first electrode surface to prevent short circuits, then short circuit prevention is improved, but static electricity damages the TFT array in top-emission devices
Solution Approach 1:
The patent introduces carrier transporting layers as intermediary substances between the potentially rough first electrode surface and the optical resonator structure. These layers provide a buffer that prevents short circuits without requiring aggressive surface polishing, thereby avoiding static electricity generation that could damage the TFT array in top-emission devices.
Solution Approach 2:
The patent designs the organic layer structure with built-in carrier transporting layers that proactively compensate for surface unevenness before short circuits can occur. This preliminary structural design eliminates the need for post-fabrication polishing processes that generate harmful static electricity.
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 enhances light-outcoupling efficiency over a wide wavelength range, improving luminous efficiency while preventing short circuits and maintaining high resistance, thus increasing the fabrication yield of organic electroluminescent devices.
Implementation Method 1
the part between the light-transmissible second electrode and the light-reflecting layer forming an optical resonator enhancing light emitted from the organic emitting layer
Implementation Method 2
only light having a specific wavelength is intensified by utilizing a multiple interference effect and outcoupled from the EL device
Data Source
AI summary
An organic electroluminescent device including a first electrode (11), a second electrode (16), and an organic material layer (20) interposed therebetween; the second electrode (16) being light-transmissible; the organic material layer (20) having a structure wherein a first carrier transporting layer (12), an organic emitting layer (14) and a second carrier transporting layer (15) are stacked in this order; the organic material layer (20) including a conductive light-reflecting layer (13) therein; and the part between the light-transmissible second electrode (16) and the light-reflecting layer (13) forming an optical resonator enhancing light emitted from the organic emitting layer (14).