Light Emitting Device Donor Acceptor Layer Work Function
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Solution Overview
Problem
The existing thin-film light emitting elements require specific work functions for electrodes, limiting the range of material choices and complicating the selection process due to the need for materials with specific properties for each layer.
Innovation Solution
A light emitting device structure is developed where layers with donor and acceptor levels are sequentially laminated between electrodes, allowing for the selection of electrode materials regardless of work function, by injecting holes and electrons in specific layers to facilitate light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If electrode materials are selected based on specific work function requirements, then light emission efficiency is improved, but the range of material choices is narrowed
Solution Approach 1:
The patent introduces a hole injecting layer as an intermediary between the electrode and the light emitting layer. This layer mediates the interaction between the electrode and the organic compound layer, enabling hole injection without requiring the electrode material to have specific work function properties. The hole injecting layer contains a host compound and a dopant compound that facilitates hole generation and injection into the light emitting layer, thus resolving the contradiction by decoupling the electrode material selection from work function constraints.
2Reliability
If multiple layers with different properties are formed to improve light emission, then manufacturing complexity increases
Solution Approach 1:
The patent combines the hole injecting function and the light emitting function into a integrated structure. The hole injecting layer is formed by sequentially depositing a host compound layer and a dopant compound layer, where the dopant layer is deposited on top of the host layer. This merging approach allows the device to achieve efficient light emission through the electrophosphorescent mechanism while maintaining a relatively simple manufacturing process using conventional vacuum deposition techniques.
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 widens the range of choices for electrode materials, enabling the use of suitable materials for the light emitting device structure without regard for work function, improving the efficiency and flexibility of the light emitting device.
Implementation Method 1
The first layer is a layer having a donor level. The third layer is a layer having an acceptor level. When a potential of the second electrode is set higher than that of the first electrode, holes generated in the second layer are injected in the third layer.
Implementation Method 2
a light emitting element that emits light when current flows therethrough, wherein a thin film including a light emitting substance is sandwiched between electrodes
Data Source
AI summary
An object of the present invention is to provide a light emitting element or a light emitting device that can be formed without any regard for a work function of an electrode. Another object of the invention is to provide a light emitting element or a light emitting device in that the range of choice for a material of an electrode can be widened. In an aspect of the invention, a light emitting device includes first, second and third layers between mutually-facing first and second electrodes. The first layer has a donor level. The second layer is a single layer or a laminated body containing a light emitting substance. The third layer has an acceptor level. When a potential of the second electrode is set higher than that of the first electrode, holes generated in the second layer are injected in the third layer.