Top-Emission Organic EL Device with Optimized Optical Distances
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Solution Overview
Problem
Top emission white organic electroluminescent (EL) devices face challenges in producing both blue and red/green light interference effects while maintaining low power consumption and durability, due to the placement of a hole transporting blue-light-emitting layer on the cathode side, which affects the optical distances and layer thicknesses, leading to increased voltage and potential short circuits.
Innovation Solution
A top emission organic EL device is designed with a hole transporting blue-light-emitting layer on the cathode side and a red/green-light-emitting layer on the anode side, optimizing the optical distances to achieve constructive interference for both blue and red/green light emissions, reducing light-emitting voltage, and enhancing durability by using a reflection electrode as a cathode and a light extraction electrode as an anode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a hole transporting blue-light-emitting layer is placed on the cathode side in a top emission organic EL device, then the durability is improved, but the light-emitting voltage increases and power consumption increases
Solution Approach 1:
The patent optimizes the thickness of the blue-light-emitting layer and the optical distance from the reflection electrode to achieve constructive interference for blue light. By precisely controlling these parameters, the device achieves both high durability and low power consumption, resolving the contradiction between reliability and energy usage.
2Use of energy by moving object
If the optical distance from the reflection electrode to the blue-light-emitting layer is optimized for constructive interference, then the power consumption is reduced, but it becomes difficult to achieve constructive interference for red/green light simultaneously
Solution Approach 1:
The patent divides the light-emitting function into separate layers: a blue-light-emitting layer optimized for blue wavelength interference and a red/green-light-emitting layer optimized for red/green wavelengths. This segmentation allows each layer to be independently optimized, enabling both blue and red/green constructive interference effects to coexist, thus resolving the contradiction between energy efficiency and multi-wavelength adaptability.
3Productivity
If the blue-light-emitting layer thickness is increased to achieve constructive interference, then the blue light emission efficiency is improved, but the risk of short circuits increases
Solution Approach 1:
The patent precisely controls the thickness of the blue-light-emitting layer to a specific range that achieves constructive interference for blue light while maintaining sufficient insulation. This parameter optimization resolves the contradiction between productivity (emission efficiency) and reliability (short circuit prevention) by finding the optimal thickness value that satisfies both requirements.
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 enables the production of both blue and red/green light interference effects, reducing power consumption and improving durability by minimizing voltage requirements and preventing short circuits, while maintaining high chromaticity and efficiency.
Implementation Method 1
an organic electroluminescent (EL) device that emits light by passing a current through an organic light-emitting layer sandwiched between a pair of electrodes
Implementation Method 2
optimizing the optical distances to achieve constructive interference for both blue and red/green light emissions
Data Source
AI summary
An organic EL device includes a substrate, a reflection electrode, an organic compound layer and a light extraction electrode in this order. The organic compound layer includes a first light-emitting layer which is electron trapping type light-emitting layer and a second light-emitting layer disposed between the reflection electrode and the first light-emitting layer. An optical distance between the reflection electrode and the first light-emitting layer is a distance of constructive interference for the light of the first light-emitting layer.