OLED Pixel Circuit Charge Injection via Salt Mediator
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Solution Overview
Problem
Quantum dot light emitting diodes (QLEDs) face low charge injection efficiency due to mismatched highest occupied molecular orbital (HOMO) energy levels between the hole transport layer and the quantum dot light emitting layer, leading to unbalanced charge injection and reduced light emitting efficiency and lifetime compared to conventional OLEDs.
Innovation Solution
A pixel circuit with a reset module, data write module, storage module, compensation and hold module, and drive module is designed to generate and store a control voltage, allowing the drive module to produce a drive current equal to the data current, thereby increasing charge injection into the light emitting device without increasing power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the HOMO energy level of the hole transport layer is increased to match the quantum dot light emitting layer, then charge injection efficiency is improved, but material synthesis difficulty increases
Solution Approach 1:
The patent introduces an intermediary substance (salt) that mediates between the hole transport layer and quantum dot light emitting layer. The salt forms a complex with the hole transport material, creating an intermediate state that facilitates charge injection without requiring modification of the original materials' HOMO energy levels, thus avoiding synthesis difficulties while improving charge injection efficiency
Solution Approach 2:
The patent changes the chemical parameter of the hole transport layer by introducing salt to form a complex. This parameter change (formation of salt complex) modifies the energy level characteristics and charge injection properties without requiring synthesis of new materials, thereby improving charge injection efficiency while maintaining ease of manufacture
2Reliability
If a multilayer hole transport layer is provided to increase hole mobility and injection efficiency, then charge injection is improved, but process complexity increases
Solution Approach 1:
The patent segments the hole transport function into two parts: the original hole transport layer and a salt layer added on top. This segmentation allows each layer to perform its function independently - the original layer provides hole transport while the salt layer enhances injection efficiency - without requiring complex integration of multiple functional layers
Solution Approach 2:
The salt acts as an intermediary layer between the hole transport layer and quantum dots, simplifying the overall structure compared to multilayer hole transport designs. The salt mediates charge transfer without requiring complex multilayer architectures, thus improving injection efficiency while maintaining process simplicity
3Reliability
If an electronic barrier layer is provided to slow down electron injection rate, then recombination efficiency is improved, but light emitting efficiency cannot be increased
Solution Approach 1:
The patent converts the potential harm of unbalanced charge injection into benefit by using salt to create a controlled imbalance that favors hole injection. The salt complex selectively enhances hole transport while maintaining electron injection, transforming the charge injection imbalance problem into a solution that improves both recombination efficiency and light emitting efficiency simultaneously
Data Source
AI summary
The disclosure provides a pixel circuit including a reset module, a data write module, a storage module, a compensation and hold module, a drive module, and a light emitting device. The reset module is connected to the storage module and the light emitting device. The data write module is connected to the drive module. The compensation and hold module is connected to the drive module and the storage module. The storage module is connected to the drive module. The drive module is connected to the light emitting device.