Tandem OLED Charge Generation Layers for Low Voltage
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Solution Overview
Problem
Tandem organic light-emitting diodes require high driving voltage for normal luminescence, leading to high energy consumption due to inefficient carrier injection.
Innovation Solution
A tandem organic light-emitting diode structure comprising an anode, hole transport layer, first and second light-emitting layers, N-type and PN junction type bulk heterojunction charge generation layers, and a P-type bulk heterojunction charge generation layer, which form multiple exciton-forming interfaces to increase carrier generation and reduce binding, allowing for lower driving voltage and reduced power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a tandem organic light-emitting diode structure is used to achieve multiple light-emitting layers, then the luminous efficiency and color gamut are improved, but the driving voltage increases leading to high energy consumption
Solution Approach 1:
The charge generation layer is divided into multiple independent bulk heterojunction segments (first, second, third, and fourth charge generation layers) with different material compositions. Each segment independently generates carriers for specific light-emitting layers, reducing the overall driving voltage requirement while maintaining efficient carrier injection across multiple emitting zones.
Solution Approach 2:
Different regions of the charge generation layers use different organic material proportions (P-type vs N-type materials) optimized for specific functions. The first and fourth charge generation layers use one material proportion configuration, while the second and third layers use different configurations, allowing localized optimization of carrier generation efficiency at each interface.
2Illumination intensity
If high driving voltage is applied to achieve normal luminescence in tandem OLEDs, then the luminescence intensity is improved, but the carrier injection efficiency remains low leading to wasted energy
Solution Approach 1:
The charge generation system is segmented into multiple bulk heterojunction layers, each independently providing carrier generation capability. This segmentation allows efficient carrier injection at lower voltages while maintaining high luminescence intensity through cumulative emission from multiple light-emitting layers.
Solution Approach 2:
The charge generation layers use composite organic materials with different proportions of P-type and N-type materials. This composite approach creates bulk heterojunctions with optimized charge separation and transport properties, enhancing carrier injection efficiency without requiring high driving voltages.
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 structure enhances carrier injection efficiency, enabling normal luminescence at a lower driving voltage and reducing power consumption, as evidenced by a driving voltage of about 5.5 V and power efficiency of 6.4 lm/W in blue light-emitting diodes.
Implementation Method 1
form multiple exciton-forming interfaces to increase carrier generation and reduce binding
Implementation Method 2
tandem organic light-emitting diode structure comprising an anode, hole transport layer, first and second light-emitting layers
Data Source
AI summary
A tandem organic light-emitting diode, an array substrate and a display device are provided. The tandem organic light-emitting diode includes an anode, a hole transport layer, a first light-emitting layer, a first charge generation layer, a second charge generation layer, a third charge generation layer, a fourth charge generation layer, a second light-emitting layer, an electron transport layer and a cathode which are sequentially laminated, wherein the first charge generation layer is an N-type bulk heterojunction, the second charge generation layer and the third charge generation layer are both PN junction type bulk heterojunctions, a proportion of the P-type organic material in the second charge generation layer is greater than that of the N-type organic material, a proportion of the P-type organic material in the third charge generation layer is less than that of the N-type organic material, and the fourth charge generation layer is a P-type bulk heterojunction.