Quantum Dot Light Emitting Element Voltage Control
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Solution Overview
Problem
The luminous efficiency of quantum dot-based light emission layers in display devices is limited by charge carrier balance, exciton confinement, and leakage current, leading to reduced emission efficiency and shorter lifespan due to charging phenomena.
Innovation Solution
A display device with a light emitting element featuring a quantum dot layer, where the voltage applied to the electrodes during emission and non-emission periods is optimized to enhance charge carrier transport and reduce leakage current, including applying a higher voltage to the anode during emission and a higher voltage to the cathode during non-emission, and extending the emission period relative to the non-emission period within a frame.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a quantum dot emission layer is used to reduce manufacturing cost and achieve desired color, then manufacturing cost decreases and color control improves, but luminous efficiency is limited by charge carrier balance and leakage current
Solution Approach 1:
The patent applies periodic action by alternating between emission periods and non-emission periods in a frame-based driving scheme. During emission periods, voltage is applied to generate light; during non-emission periods, voltage is reduced or reversed to allow charge carrier relaxation and prevent accumulation. This periodic operation resolves the contradiction by enabling efficient emission when needed while preventing degradation that would reduce long-term efficiency.
Solution Approach 2:
The patent implements dynamics by dynamically adjusting voltage parameters based on the operational state (emission vs. non-emission period). The voltage applied to the first and second electrodes is varied according to the timing signal, transitioning between high voltage during emission and low or reversed voltage during non-emission periods. This dynamic control optimizes charge carrier balance and prevents leakage current accumulation, thereby maintaining high luminous efficiency.
2Use of energy by moving object
If charge carriers are confined to the emission layer to improve quantum efficiency, then emission efficiency increases, but charging phenomena cause degradation and reduce lifespan
Solution Approach 1:
The periodic emission and non-emission periods allow charge carriers to be confined to the emission layer during emission periods for efficient light generation, while providing regular intervals during non-emission periods for charge carriers to relax and discharge. This prevents permanent charging accumulation that would cause degradation, thereby extending device lifespan while maintaining high emission efficiency.
Solution Approach 2:
The patent employs feedback mechanisms through timing signals that monitor and control the voltage application based on the operational state. The timing signal generates appropriate voltage patterns that provide feedback control over charge carrier injection and extraction, ensuring optimal charge balance and preventing accumulation effects that would reduce reliability.
3Illumination intensity
If voltage is continuously applied to maintain emission, then light output is sustained, but leakage current increases and causes charging phenomena
Solution Approach 1:
The patent uses periodic action by applying voltage only during emission periods and reducing or reversing voltage during non-emission periods. This timing-controlled voltage application maintains high light output during emission while allowing leakage current to be minimized during non-emission periods, preventing charge carrier accumulation and its harmful effects.
Solution Approach 2:
The patent applies preliminary action by preparing the emission layer and charge carriers in advance during non-emission periods before the next emission period begins. This allows charge carriers to be positioned optimally and leakage current to be managed in advance, ensuring clean emission without harmful charging effects when voltage is subsequently applied.
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 improves the emission efficiency and extends the lifespan of the light emitting element by eliminating interface charging and reducing degradation, thereby enhancing the overall display quality.
Implementation Method 1
A quantum dot is a nanocrystal of a semiconductor material with a diameter of about 10 nanometers (nm) or less, and is a material that has a quantum confinement effect
Implementation Method 2
Light emission of the quantum dots is generated when excited electrons transition from a conduction band to a valence band
Implementation Method 3
Luminous efficiency of an emission layer including a quantum dot is determined by quantum efficiency of the quantum dot, charge carrier balance, light extraction efficiency, and leakage current
Data Source
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AI summary
A light emitting element includes a first electrode, a second electrode, and a light emission layer interposed between the first electrode and the second electrode, where an emission efficiency of the light emission layer varies based on a voltage applied to at least one selected from the first electrode and the second electrode.