Tandem Light-Emitting Device Charge Generation Structure
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Solution Overview
Problem
Conventional light-emitting devices with single stack structures have limitations in efficiency, particularly in reducing driving voltage and enhancing power efficiency and current density, which are not adequately addressed.
Innovation Solution
A tandem light-emitting device structure is introduced, featuring a charge generation structure with a thickness ratio of 5:4:7 for n-type, interlayer organic, and p-type charge generation layers, and a metal layer replacing the n-type charge generation layer to lower the charge injection barrier, improving charge balance and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single stack structure is used in a light-emitting device, then the device structure is simple, but the driving voltage cannot be reduced and power efficiency is limited
Solution Approach 1:
The light-emitting device is divided into multiple independent stacks (first stack, second stack, etc.) connected in series. Each stack contains its own light-emitting layer, hole injection layer, hole transport layer, electron transport layer, and electron injection layer. This segmentation allows each stack to operate independently, improving overall power efficiency and current density while maintaining manageable structural complexity through modular design.
2Device complexity
If conventional charge generation layers are used, then the charge injection barrier is high, but the device structure is simpler
Solution Approach 1:
The charge generation structure uses specific thickness ratios (5:4:7 for n-type charge generation layer, interlayer organic layer, and p-type charge generation layer) and replaces conventional materials with optimized combinations including metal layers. These parameter changes reduce the charge injection barrier by improving charge generation and transport efficiency at the interfaces between stacks, while maintaining a relatively simple overall structure.
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 tandem structure significantly reduces driving voltage, enhances power efficiency, and increases current density, making the device more electrically and optically efficient compared to single stack devices.
Implementation Method 1
a charge generation structure between the first and second stacks including an n-type charge generation layer, an interlayer organic layer, and a p-type charge generation layer which are sequentially stacked on the first stack
Implementation Method 2
When an electric field is applied between the pair of electrodes, electrons and holes are respectively injected from an anode and a cathode into the light-emitting layer. When the electrons and the holes are recombined in the light-emitting layer, the recombination energy level returns from a conduction band to a valence band, and thus energy is released as light.
Data Source
AI summary
A light-emitting device includes a first electrode and a second electrode opposed to each other, a first stack between the first and second electrodes, the first stack being adjacent to the first electrode and including a first light-emitting layer, a second stack between the first and second electrodes, the second stack being adjacent to the second electrode and including a second light-emitting layer, and a charge generation structure between the first and second stacks, the charge generation structure including an n-type charge generation layer, an interlayer organic layer, and a p-type charge generation layer which are sequentially stacked on the first stack.