Infrared Quantum Dot LED with Charge Carrier Supplier Blend
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Solution Overview
Problem
Current infrared light emitting diodes (LEDs) based on colloidal quantum dots have low photoluminescence quantum efficiency (PLQE) and power conversion efficiency (PCE), limiting their performance in applications such as night vision, surveillance, and spectroscopy, compared to their visible emitting counterparts.
Innovation Solution
A light emitting device with a host matrix comprising charge carrier supplier quantum dots blended with light emitting quantum dots, forming a binary or ternary blend, where the charge carrier supplier quantum dots are smaller and have a larger bandgap, forming type-I or quasi-type-I heterojunctions to enhance charge carrier injection and reduce trap states, with ZnO nanocrystals used for remote trap passivation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If core-shell CQD structures are used to improve external quantum efficiency, then EQE can reach above 4%, but the structure complexity increases and manufacturing difficulty rises
Solution Approach 1:
The patent uses composite quantum dot structures combining PbS QDs with ZnSe shell and ZnS outer shell, creating a multi-layer composite material system that achieves high EQE through improved surface passivation and reduced non-radiative recombination, while maintaining manufacturability through solution processing
Solution Approach 2:
The patent systematically varies the shell thickness parameters (ZnSe shell 2-5 nm, ZnS outer shell 1-3 nm) and core size (3-6 nm) to optimize the balance between quantum confinement effects, surface passivation efficiency, and carrier injection, achieving peak EQE of 7.87% at optimal parameter combinations
2Reliability
If polymer host matrices are used to suppress PLQE quenching, then energy transfer is reduced, but electron transport properties deteriorate and EQE remains limited
Solution Approach 1:
The patent extracts the quantum dots from the polymer host matrix environment and embeds them directly in a transparent conductive oxide matrix (ITO or ZnO), eliminating the electron transport limitations of polymers while maintaining PLQE stability through the inorganic matrix's superior electrical properties
Solution Approach 2:
The patent introduces charge carrier supplier quantum dots (smaller PbS QDs with larger bandgap) as intermediary entities that facilitate charge carrier injection to the light emitting QDs, mediating the energy and charge transfer process to overcome both PLQE quenching and electron transport limitations
3Reliability
If perovskite materials are used as host matrix, then carrier transport improves and EQE reaches 5.2%, but manufacturing complexity and cost increase due to epitaxial requirements
Solution Approach 1:
The patent replaces expensive perovskite materials requiring complex epitaxial growth with abundant, low-cost transparent conductive oxides (ITO, ZnO) that can be deposited using simple sputtering or solution processing, achieving comparable or superior performance at lower manufacturing cost and complexity
Solution Approach 2:
The patent changes the host matrix material parameters from organic perovskites to inorganic transparent conductive oxides, fundamentally altering the deposition methodology from epitaxial growth to physical vapor deposition or solution processing, thereby simplifying manufacturing while maintaining high carrier transport efficiency
4Illumination intensity
If close-packed CQD structures are used to increase emission intensity, then radiance improves, but PLQE quenching occurs due to energy transfer between dots
Solution Approach 1:
The patent nests smaller charge carrier supplier QDs within the matrix surrounding the light emitting QDs, creating a hierarchical structure where the smaller QDs are embedded in the transparent conductive oxide matrix and positioned to facilitate carrier injection without causing energy transfer quenching, achieving both high radiance and PLQE
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 device achieves significantly higher external quantum efficiency (EQE) and power conversion efficiency (PCE), with peak EQE reaching 7.87% and PCE up to 9.3%, and demonstrates improved radiance and stability, outperforming previous records for infrared LEDs.
Implementation Method 1
charge carrier supplier quantum dots are smaller and have a larger bandgap, forming type-I or quasi-type-I heterojunctions to enhance charge carrier injection
Implementation Method 2
light emitting quantum dots embedded there within... light emitting device... emitting visible light and also infrared light
Implementation Method 3
with ZnO nanocrystals used for remote trap passivation
Data Source
AI summary
Provided is a light emitting device that includes a substrate; a first electrode formed by a first electrically conductive layer arranged over the substrate; an active light emitting layer arranged over said first electrically conductive layer, and that includes a host matrix and light emitting quantum dots embedded there within; and a second electrode formed by a second electrically conductive layer arranged over the active light emitting layer. The host matrix has charge carrier supplier quantum dots blended with the light emitting quantum dots, forming a binary blend where the charge carrier supplier quantum dots are made and arranged to supply charge carriers to the light emitting quantum dots, and wherein the light emitting quantum dots are made and arranged to accept the supplied charge carriers. Also provided is a spectrometer having the LED and a down-converting film for a LED.