Light-emitting element with segmented electron injection layers
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Solution Overview
Problem
In light-emitting elements with layers containing acceptor and donor substances, the interaction between these substances leads to an increase in driving voltage and power consumption, and existing structures struggle to maintain optimal color purity and efficiency when the thickness of layers between electrodes is changed.
Innovation Solution
A light-emitting element structure is implemented with a first layer containing a high hole-transporting substance and an acceptor substance, a second layer with a high electron-transporting substance, and a third layer using alkali or rare earth metals to reduce electron injection barriers, along with an electron-relay layer to facilitate efficient electron transfer and minimize interaction between the acceptor and donor substances.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a layer including an acceptor substance and a layer including a donor substance are in contact with each other to conduct optical adjustment, then the emission spectrum can be adjusted, but the driving voltage increases due to p-n junction formation and carrier movement
Solution Approach 1:
The patent divides the electron-injecting layer into multiple sub-layers: a first electron-injecting layer in contact with the cathode, a second electron-injecting layer in contact with the first layer, and an optical adjustment layer in contact with the second layer. This segmentation prevents direct contact between acceptor and donor substances, avoiding p-n junction formation while maintaining optical adjustment capability and reducing driving voltage.
2Illumination intensity
If the thickness of the layer doped with metal oxide is increased to conduct optical adjustment, then the emission spectrum can be adjusted, but the driving voltage increases
Solution Approach 1:
The patent segments the electron-injecting function from the optical adjustment function by placing the optical adjustment layer separate from the electron-injecting layers. This allows the optical adjustment layer thickness to be optimized for emission spectrum adjustment without compromising electron injection efficiency, thereby preventing driving voltage increase.
3Reliability
If acceptor and donor substances are placed in separate layers to reduce interaction, then functional interference is minimized, but additional layers increase device complexity
Solution Approach 1:
The patent uses electron-transporting substances that serve dual functions: they transport electrons and provide optical adjustment capability. This multi-functionality reduces the need for separate dedicated layers, minimizing device complexity while preventing functional interference between acceptor and donor substances.
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 structure effectively suppresses the increase in driving voltage, reduces power consumption, and maintains excellent color purity even when the thickness of layers between electrodes is altered, while ensuring efficient electron injection and minimal functional interference between the acceptor and donor substances.
Implementation Method 1
when voltage is applied to a pair of electrodes with an EL layer including a light emitter interposed therebetween, electrons injected from a cathode and holes injected from an anode are recombined at an emission center in the EL layer to form molecular exciton, and energy is released when the molecular exciton relaxes to the ground state and thus light is emitted
Data Source
AI summary
Light-emitting elements in which an increase of driving voltage can be suppressed are provided. Light-emitting devices whose power consumption is reduced by including such light-emitting elements are also provided. In a light-emitting element having an EL layer between an anode and a cathode, a first layer in which carriers can be produced is formed between the cathode and the EL layer and in contact with the cathode, a second layer which transfers electrons produced in the first layer is formed in contact with the first layer, and a third layer which injects the electrons received from the second layer into the EL layer is formed in contact with the second layer.