OLED Electron Transport Layer Gradient Composition
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Solution Overview
Problem
Current organic light emitting diode (OLED) technologies face challenges in achieving optimal carrier balance and efficiency due to electron bombardment at the interface between the light emitting layer and the electron transport layer, which affects device lifetime and performance.
Innovation Solution
An organic electroluminescent device with an electron transport layer comprising a mixture of first and second electron transport materials, where the lowest unoccupied molecular orbital (LUMO) energy level of the first material is higher than the second, and the ratio of these materials varies from the cathode to the anode, optimizing carrier balance and reducing electron bombardment through spatial adjustment of the material ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single electron transport material is used in the electron transport layer, then the device structure is simple, but carrier balance is poor and electron bombardment occurs at the interface
Solution Approach 1:
The patent uses a composite electron transport layer containing two different electron transport materials (ETM1 and ETM2) with different LUMO energy levels. This composite structure enables simultaneous optimization of carrier balance and reduction of electron bombardment, resolving the contradiction between structural simplicity and carrier balance performance.
Solution Approach 2:
The patent implements spatially varying composition ratios of ETM1 and ETM2 within the electron transport layer. By adjusting the local material distribution, the LUMO energy level is optimized at different positions: higher near the light emitting layer to reduce electron bombardment, and lower near the electron injection layer to enhance electron injection, thereby achieving carrier balance without excessive structural complexity.
2Reliability
If the LUMO energy level is reduced to enhance electron injection, then electron injection improves, but electron bombardment at the light emitting layer interface increases
Solution Approach 1:
The patent applies different LUMO energy level characteristics at different locations within the electron transport layer. Near the electron injection layer (cathode side), the LUMO energy level is lower to facilitate electron injection. Near the light emitting layer interface, the LUMO energy level is higher to reduce electron bombardment. This spatial variation in energy level profile simultaneously achieves both electron injection enhancement and electron bombardment reduction.
Solution Approach 2:
The patent changes the LUMO energy level parameter across the electron transport layer by varying the composition ratio of ETM1 and ETM2. The LUMO energy level transitions from lower values near the cathode to higher values near the light emitting layer, creating an optimized energy level gradient that resolves the contradiction between electron injection and electron bombardment.
3Object-affected harmful factors
If the LUMO energy level is increased to reduce electron bombardment, then electron bombardment decreases, but electron injection efficiency deteriorates
Solution Approach 1:
The patent implements spatially differentiated LUMO energy levels within the electron transport layer. The higher LUMO energy level near the light emitting layer reduces electron bombardment, while the lower LUMO energy level near the electron injection layer maintains efficient electron injection. This local optimization at different positions resolves the contradiction between reducing electron bombardment and maintaining electron injection efficiency.
Data Source
AI summary
The present disclosure provides an organic electroluminescent device and a manufacturing method thereof. The organic electroluminescent device includes an anode, an electron transport layer and a cathode. The material of the electron transport layer includes a mixture of a first electron transport material and a second electron transport material, the lowest unoccupied molecular orbital energy level of the first electron transport material is higher than that of the second electron transport material, and the ratio of the first electron transport material to the second electron transport material first decreases and then increases in the direction from the cathode to the anode.