Quantum Dot Multilayer Structure for Efficient Carrier Injection
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Solution Overview
Problem
Quantum dot light emitting devices (QD-LEDs) face efficiency deterioration due to a large energy band offset between the hole transport layer (HTL) and the QD light emitting layer, leading to increased turn-on voltage and decreased power efficiency.
Innovation Solution
Incorporating a QD containing layer with an energy band level different from the QD light emitting layer to reduce the band offset, improving carrier injection efficiency and optical confinement by configuring a QD multilayer structure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single QD light emitting layer is used, then the device structure is simple, but the energy band offset between HTL and QD light emitting layer is large causing efficiency deterioration
Solution Approach 1:
The QD light emitting layer is segmented into multiple sub-layers with different energy band levels. The first QD light emitting layer has an energy band level closer to the HTL, reducing the band offset at the HTL interface, while the second QD light emitting layer maintains the original emission characteristics. This segmentation resolves the contradiction by creating intermediate energy levels without significantly increasing structural complexity.
Solution Approach 2:
The first QD light emitting layer acts as an intermediary layer between the HTL and the second QD light emitting layer. It provides an intermediate energy band level that facilitates carrier injection from the HTL while maintaining optical confinement, thus reducing the harmful energy band offset effect without requiring complete structural redesign.
2Productivity
If multiple QD light emitting layers are used, then carrier injection efficiency is improved, but device complexity increases
Solution Approach 1:
Different regions of the QD light emitting layer are assigned different energy band levels. The first QD light emitting layer (closer to HTL) has an energy band level optimized for carrier injection, while the second QD light emitting layer has an energy band level optimized for light emission. This local quality differentiation improves carrier injection efficiency without requiring complete restructuring of the entire device.
Solution Approach 2:
The solution adds a new dimension to the device structure by introducing energy band level variation within the QD light emitting layer. Instead of simply increasing the number of layers, the patent utilizes the energy band level dimension to optimize both carrier injection and light emission functions within a relatively compact multilayer 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 QD multilayer structure enhances carrier injection and light emission efficiency, lowers turn-on and operating voltages, and improves the overall performance of QD-LEDs by effectively confining electrons and holes within the QD light emitting layer.
Implementation Method 1
a first QD light emitting layer and a second QD light emitting layer which are sequentially stacked on the substrate, the first QD light emitting layer having a first energy band level and the second QD light emitting layer having a second energy band level different from the first energy band level
Implementation Method 2
A QD is a particle formed of a semiconductor material having a crystal structure of a size smaller than the radius of a Bohr exciton... the energy levels of electrons are discontinuously limited so that electric and optical characteristics of the QD may be different from those of a semiconductor in a bulk state
Data Source
Figure 1~2
Figure 3
Figure 4A~4C
AI summary
A quantum dot light emitting device (10) includes; a substrate (12), a first electrode (14) disposed on the substrate (12), a second electrode (22) disposed substantially opposite to the first electrode (14), a first charge transport layer (15) disposed between the first electrode (14) and the second electrode (22), a quantum dot light emitting layer (18) disposed between the first charge transport layer (15) and one of the first electrode (14) and the second electrode (22), and at least one quantum dot including layer (17) disposed between the quantum dot light emitting layer (18) and the first charge transport layer (15), wherein the at least one quantum dot including layer (17) has an energy band level different from an energy band level of the quantum dot light emitting layer (18).