Quantum Dot Light-Emitting Structure for Balanced Blue Luminance
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Solution Overview
Problem
In light-emitting devices with different emission wavelengths, the use of metal chalcogenides in hole transport layers results in reduced luminance for the wavelength band with the shortest peak emission, due to charging effects and degradation of quantum dots.
Innovation Solution
A light-emitting device structure is implemented where the light-emitting elements with a metal chalcogenide hole transport layer have an intermediate organic layer with varying thicknesses, specifically a greater thickness for the element with the shortest peak emission wavelength, to balance luminance across different wavelength bands.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the thickness of quantum dot shell is increased to suppress light emission quenching and device performance degradation, then reliability is improved, but luminance of the light-emitting element with shortest emission wavelength lowers
Solution Approach 1:
The patent applies different intermediate layer thicknesses to different wavelength regions. Specifically, the intermediate layer in the blue light-emitting element (shortest wavelength) has a thickness of 5-20 nm, while intermediate layers in green and red elements have thicknesses of 1-5 nm. This local differentiation resolves the contradiction by providing enhanced protection only where most needed (blue region with shortest wavelength) while maintaining optimal luminance in other regions.
2Productivity
If a metal chalcogenide layer is used for hole transport, then charge transport efficiency is improved, but charging effects and quantum dot degradation occur leading to reduced luminance
Solution Approach 1:
The patent introduces an intermediate layer made of organic material (such as Alq3, BCP, or TPBi) between the metal chalcogenide hole transport layer and the quantum dot light-emitting layer. This intermediary layer acts as a buffer that prevents direct harmful interactions between the metal chalcogenide and quantum dots, thereby maintaining charge transport efficiency while preventing charging effects and quantum dot degradation that would otherwise reduce luminance.
3Productivity
If the distance from carrier transport layer to quantum dot core is shortened to improve characteristics, then device performance is improved, but light emission quenching occurs
Solution Approach 1:
The intermediate layer serves as a mediator that enables the carrier transport layer to be positioned closer to the quantum dot core for improved charge transport, while simultaneously preventing light emission quenching. The organic material in the intermediate layer (5-20 nm thick in blue elements) provides a protective barrier that maintains optimal distance for charge transfer while preventing harmful interactions that would quench light emission.
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 configuration achieves balanced luminance between light-emitting elements by optimizing the carrier balance and reducing charging effects, thereby improving the recombination efficiency and maintaining equivalent luminance across all emission wavelengths.
Implementation Method 1
a light-emitting device including a plurality of types of light-emitting elements each having a light emission peak wavelength in a different wavelength band
Implementation Method 2
a layer having hole transport properties and including a metal chalcogenide being between the anode and the light-emitting layer
Data Source
AI summary
A light-emitting device includes an HTL including a metal chalcogenide between an anode and an EML, with an IL including an organic material at least between the HTL and the EML. A distance between the HTL and the EML in a light-emitting element that emits light in a wavelength band having the shortest light emission peak wavelength is greater than a distance between the HTL and the EML in each of the other light-emitting elements.