QLED Mixed Light-Emitting Layer Carrier Balance
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Solution Overview
Problem
Current QLED devices face challenges in achieving optimal carrier balance due to the lower valence band energy level of quantum dot materials, leading to increased non-radiative Auger recombination and reduced luminous efficiency, primarily due to imbalanced hole and electron injection.
Innovation Solution
A mixed light-emitting layer is formed by doping a quantum dot material with a second hole transporting material having a valence band energy level between the valence band energy levels of the quantum dot and first hole transporting materials, creating a stepped barrier to enhance hole injection and block excessive electron injection, thereby promoting carrier balance and recombination efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If quantum dot material is used in QLED devices, then color purity and emission wavelength tunability are improved, but carrier balance deteriorates due to lower valence band energy level
Solution Approach 1:
A first hole transporting material is introduced as an intermediary layer between the quantum dot light-emitting layer and the hole injection layer. This intermediate layer has a valence band energy level higher than the quantum dot material but lower than the hole injection layer, creating a stepped energy level structure that facilitates hole injection while blocking excessive electron injection, thereby improving carrier balance without compromising the color purity benefits of quantum dot materials
Solution Approach 2:
The energy level parameters of the hole transporting layer are specifically optimized by selecting materials with appropriate valence band energy levels. The first hole transporting material is chosen to have a valence band energy level that is higher than the quantum dot material (to facilitate hole injection) but lower than the hole injection layer (to create a stepped barrier), thus adjusting the energy level parameters to resolve the carrier balance issue while maintaining color purity
2Adaptability or versatility
If quantum dot material with lower valence band energy level is used, then emission wavelength tunability is improved, but non-radiative recombination increases
Solution Approach 1:
The first hole transporting material serves as a mediator that creates a stepped energy level barrier, preventing excessive electron injection into the quantum dot layer. This reduces the probability of non-radiative Auger recombination processes while preserving the emission wavelength tunability of the quantum dot material through proper energy level matching
Solution Approach 2:
The hole transporting layer is designed with specific local properties (valence band energy level higher than quantum dot material) to create a localized energy barrier at the interface. This local quality adjustment addresses the non-radiative recombination issue at the critical interface region without affecting the bulk optical properties and emission wavelength tunability of the quantum dot material
3Quantity of substance
If electron injection is not blocked, then carrier density is maintained, but carrier balance deteriorates and luminous efficiency decreases
Solution Approach 1:
The valence band energy level parameter of the first hole transporting material is specifically changed to be higher than that of the quantum dot material, creating an energy barrier that selectively blocks excessive electron injection. This parameter change maintains appropriate carrier density while improving carrier balance and luminous efficiency by preventing carrier imbalance
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 luminous efficiency and brightness of QLED devices by balancing carriers in the light-emitting layer, reducing non-radiative recombination processes and enhancing the overall performance.
Implementation Method 1
doping a quantum dot material with a second hole transporting material having a valence band energy level between a valence band energy level of the quantum dot material and a valence band energy level of the first hole transporting material; using a stepped barrier between the first hole transporting material and the doped second hole transporting material enhances hole injection
Implementation Method 2
the first hole transporting material with a higher valence band energy level can block the electrons on one side of the hole transport layer close to the cathode to weaken the injection of electrons into the mixed emitting layer
Implementation Method 3
improving the carrier recombination efficiency, and then improving the luminous efficiency and brightness of the QLED device
Data Source
AI summary
The disclosure provides a fabricating method of a QLED device and a QLED device. In the fabricating method of a QLED device, a mixed light-emitting layer is formed by doping a quantum dot material with a second hole transporting material having a valence band energy level between the quantum dot material and the first hole transporting material; a stepped barrier between the first hole transporting material and the doped second hole transporting material is used to enhance the hole injection; simultaneously, the first hole transporting material with a higher valence band energy level can block the electrons on one side of the hole transport layer close to the cathode to weaken the injection of electrons into the mixed light-emitting layer, thereby promoting the balance of carriers in the mixed light-emitting layer, improving the carrier recombination efficiency, and then improving the luminous efficiency and brightness of the QLED device.