QLED Second Carrier Blocking Layer for Injection Balance
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Solution Overview
Problem
Conventional quantum dot light-emitting diodes (QLEDs) face inefficiencies due to unbalanced electron and hole injection, leading to energy consumption as heat and subpar performance compared to OLEDs, primarily because of the large hole injecting barrier and low mobility of organic hole transporting materials.
Innovation Solution
Incorporating a second carrier blocking layer between the light-emitting layer and the second electrode to reduce the injecting efficiency of the second carrier, thereby improving the balance between electron and hole injection, and using materials like MgF2, AlF3, or SiO2 formed by vacuum or electron beam evaporation to block electrons effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a conventional organic-inorganic hybrid QLED device uses ZnO nano-particles for electron transporting and organic hole transporting materials, then electron mobility is improved (10^-3 cm²V^-1S^-1), but hole injecting and transporting become unfavorable due to large hole injecting barrier (−5.0-6.0 eV HOMO vs −6.0-7.0 eV valence band) and low mobility (−4 cm²V^-1S^-1), leading to unbalanced carrier injection
Solution Approach 1:
The patent introduces a hole transporting layer between the anode and light emitting layer to serve as an intermediary that facilitates hole injection and transport. This mediator layer with appropriate HOMO level (−5.0 to −6.0 eV) and mobility (≥10^-4 cm²V^-1S^-1) bridges the gap between the anode and quantum dots, resolving the unbalanced carrier injection issue caused by the large hole injecting barrier in conventional structures.
2Loss of energy
If organic hole transporting materials are used with HOMO in range of −5.0-6.0 eV, then hole injecting barrier is reduced, but mobility remains low (−4 cm²V^-1S^-1), still not favorable for hole injecting and transporting
Solution Approach 1:
The patent specifies precise parameter ranges for the hole transporting layer materials: HOMO level between −5.0 to −6.0 eV and mobility ≥10^-4 cm²V^-1S^-1. By changing and optimizing these material parameters, the invention simultaneously reduces the hole injecting barrier and improves hole mobility, overcoming the limitations of conventional organic hole transporting materials.
3Productivity
If electron injecting efficiency is high compared to hole injecting efficiency, then electron transport is facilitated, but energy is consumed in the form of heat due to unbalanced injection
Solution Approach 1:
The patent applies preliminary anti-action by introducing a hole transporting layer that proactively addresses the hole injection deficiency before carrier recombination occurs. This pre-compensation mechanism balances the carrier injection rates, preventing the energy loss as heat that would otherwise result from unbalanced electron-hole injection in conventional QLED devices.
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 enhances light output efficiency, increases brightness and lifetime, and improves stability against water and oxygen erosion, resulting in a more efficient and longer-lasting QLED.
Implementation Method 1
a second carrier blocking layer, which is arranged between the light emitting layer and the second electrode, and is configured to block a portion of the second carrier from being transported to the light emitting layer
Implementation Method 2
a first carrier transporting layer, which is arranged between the first electrode and the light emitting layer, and is configured to transport a first carrier injected from the first electrode to the light emitting layer
Implementation Method 3
a second carrier transporting layer, which is arranged between the light emitting layer and the second electrode, and is configured to transport a second carrier injected from the second electrode to the light emitting layer
Implementation Method 4
using materials like MgF2, AlF3, or SiO2 formed by vacuum or electron beam evaporation
Implementation Method 5
using materials like MgF2, AlF3, or SiO2 formed by vacuum or electron beam evaporation
Data Source
AI summary
A light-emitting diode, a method for fabricating the same, and a display device are disclosed. The light-emitting diode includes a first and second electrode; a first carrier transporting layer, a light emitting layer, and a second carrier transporting layer which are arranged between the first and second electrode in this order The light-emitting diode further includes a second carrier transporting layer which is arranged between the light emitting layer and the second electrode. The second carrier blocking layer blocks a portion of the second carrier from being transported to the light emitting layer. This decreases the injecting efficiency of the second carrier, improves an injecting balance between the second carrier and the first carrier with a low injecting efficiency, avoids energy consumption in the form of heat, and increases the light output efficiency and lifetime of the light-emitting diode.