Tandem OLED Connecting Layer Reduces Driving Voltage
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Solution Overview
Problem
Tandem organic light emitting devices face a challenge in increasing luminous efficiency without increasing current density, as existing methods require a corresponding increase in operation voltage, limiting their application in display devices.
Innovation Solution
A tandem organic light emitting device structure is developed with non-doping materials having both hole and electron transporting abilities for the hole and electron injection layers, which contact with a connecting layer, reducing the energy difference and thereby minimizing the increase in operation voltage when adding more emitting units.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If series connecting OLED units to form tandem OLED is used to increase luminous efficiency, then luminous efficiency increases by several folds, but operation voltage increases by the same folds
Solution Approach 1:
The patent introduces a connecting layer as an intermediary component between multiple OLED units. This connecting layer includes a hole blocking layer and an electron blocking layer that facilitate charge recombination and reduce energy loss at the interface, thereby lowering the voltage penalty typically associated with series-connected tandem structures
Solution Approach 2:
The patent modifies the energy level parameters of the injection layers and connecting layers to achieve better energy alignment. By adjusting the HOMO and LUMO levels of the organic materials used in the connecting layer, the patent reduces the energy barrier for charge injection and recombination, which decreases the operation voltage while maintaining high luminous efficiency
2Productivity
If current density is increased to improve current efficiency, then current efficiency increases, but light-emitting period decreases
Solution Approach 1:
The patent divides the device into multiple independent OLED units connected in a specific configuration with connecting layers. This segmentation allows each unit to operate at optimized current densities while the overall device achieves high current efficiency through the combined output of multiple units, preventing the need to overdrive individual units which would reduce their lifetime
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 enhances luminous efficiency and current density without doubling the operation voltage, enabling the use of more emitting units without the theoretical fold increase in voltage, thus improving the performance and commercial viability of OLEDs.
Implementation Method 1
The material for hole injection layer and electron injection layer contacting with connecting layer in the organic light emitting device of the present invention is a non-doping material having both hole transporting and electron transporting abilities
Implementation Method 2
an organic light emitting layer
Data Source
AI summary
The present invention relates to a tandem organic light emitting device, which reduces the driving voltage by using a non-doping material having both the electron transporting and hole transporting abilities to act, respectively, as an electron transporting layer and a hole transporting layer that are in contact with the connecting layer. The tandem organic light emitting device does not have to double its driving voltage as a result of the increasing of the number of the emitting element contained therein. However, the brightness and the current efficiency of the device of the present invention will be higher than the theoretical fold value calculated in accordance with the number of emitting element contained in the device.