OLED Common Emission Layer P-Type Dopant Hole Transport
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Solution Overview
Problem
The hole transporting efficiency in organic light-emitting devices with a blue emission layer as a common layer is reduced due to the host and dopant combination, which affects the overall performance of the device.
Innovation Solution
Incorporating a p-type dopant with a specific energy level into the blue common emission layer, along with a host and a red or green common emission layer, to enhance hole transporting efficiency across different emission regions, with the p-type dopant having a LUMO energy level difference of 0.2 to 1.0 eV from the HOMO energy level of the host, and being present in amounts of 0.5 to 3 wt %.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a blue emission layer as a common layer includes a host and a dopant to control emission wavelength, then emission wavelength control is improved, but hole transporting efficiency is reduced
Solution Approach 1:
The patent introduces a p-type dopant with specifically controlled energy levels (LUMO energy level difference of 0.2 to 1.0 eV from the HOMO energy level of the host) to modify the electrical parameters of the common emission layer. This parameter change enables the layer to maintain both its emission wavelength control capability and improved hole transporting efficiency, resolving the contradiction between these two functions.
2Ease of manufacture
If a common emission layer is used across red, green, and blue emission regions to simplify patterning, then manufacturing complexity is reduced, but hole transporting efficiency is reduced
Solution Approach 1:
The patent creates a composite emission layer by combining the host material, emission dopant, and p-type dopant in specific proportions. This composite structure maintains the simplification benefits of a common layer across all emission regions while the p-type dopant component specifically enhances hole transporting efficiency, resolving the contradiction between manufacturing ease and device performance.
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 increases hole transporting efficiency, ensuring that holes injected from the anode can reach the red and green emission layers without significant reduction in speed, thereby improving the device's performance.
Implementation Method 1
a difference between the lowest unoccupied molecular orbital (LUMO) energy level of the p-type dopant and the highest occupied molecular orbital (HOMO) energy level of the first host may range from about 0.2 to about 1.0 eV
Implementation Method 2
An electron-hole pair recombined in a certain molecule forms a molecular exciton in a high-energy excited state. The molecular excitons emit unique wavelengths of light upon returning to a low-energy ground state.
Data Source
AI summary
An organic light-emitting device includes a substrate; a first electrode layer and a second electrode layer on the substrate, in parallel to the substrate, and facing each other; an emission layer between the first electrode layer and the second electrode layer, where the emission layer includes a first emission region, a second emission region, and a third emission region, where the emission layer includes a first common emission layer in the first emission region, the second emission region, and the third emission region; a second emission layer in the second emission region between the first common emission layer and the second electrode layer; and a third emission layer in the third emission region between the first common emission layer and the second electrode layer, and where the first common emission layer includes a first host, a first dopant, and a p-type dopant.