Top-Emission OLED Electron Transport Layers for Efficiency and Voltage
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Solution Overview
Problem
Existing single-emission-layer top emission OLEDs face challenges in efficiency and voltage performance.
Innovation Solution
An organic light emitting diode (OLED) structure featuring a non-transparent substrate, an anode, a cathode, an emission layer, and an electron transport layer stack comprising a first and second electron transport layer, where the first layer includes a compound of Formula (I) and the second layer includes a compound of Formula (II), both without electrical dopants, with specific molecular structures and dipole moments to enhance electron transport efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electron transport layer is used in top emission OLEDs, then the device structure is simple, but the efficiency and voltage performance are insufficient
Solution Approach 1:
The electron transport layer is divided into multiple sub-layers (first electron transport layer, second electron transport layer, and third electron transport layer) with different materials and functions. This segmentation allows optimization of electron transport at different interfaces and regions, improving overall device efficiency while managing complexity through functional specialization.
Solution Approach 2:
The patent uses composite material structures in the electron transport layers, combining different organic compounds with specific molecular weights and dipole moments. The first electron transport layer uses compounds with molecular weight 150-300 Da, the second uses 200-400 Da, and the third uses 180-350 Da, creating a composite system that optimizes both electron transport and device performance.
2Device complexity
If conventional electron transport materials are used, then the device structure is straightforward, but the operating voltage remains high
Solution Approach 1:
The patent systematically changes molecular parameters of electron transport materials, specifically controlling molecular weight (150-350 Da range) and dipole moment (1.0-3.0 Debye range) across different layers. These parameter optimizations reduce electron transport barriers and improve interfacial energy level alignment, thereby reducing operating voltage without complicating the device structure.
Solution Approach 2:
Different electron transport layers are assigned specific material properties tailored to their local functions. The first layer near the emission layer uses compounds optimized for electron injection, the second layer in the middle uses compounds for electron transport, and the third layer near the electron injection layer uses compounds for electron extraction. This local optimization reduces overall operating voltage.
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
Improves the efficiency and reduces the operating voltage of the OLED device by optimizing electron transport layers with specific compounds, enhancing performance.
Implementation Method 1
The holes and electrons recombine in the EML to generate excitons. When the excitons drop from an excited state to a ground state, light is emitted.
Data Source
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AI summary
The present invention relates to an organic light emitting diode comprising a non-transparent substrate, an anode, a cathode, an emission layer, an electron injection layer and an electron transport layer stack; and to a display device or lighting device comprising the same.