OLED Emissive Region Energy Level Alignment for Narrow Spectrum
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Solution Overview
Problem
Conventional OLEDs face challenges in achieving a narrow emission spectrum and suppressing exciplex formation, which can lead to contamination of the emission spectrum and reduced color saturation, especially in blue micro-cavity OLEDs.
Innovation Solution
The OLED design incorporates a singlet or doublet fluorescent emitter with a high HOMO and low LUMO energy, where the emitter material's energy gap is optimized to ensure that the emission spectrum is dominated by the emitter, with a root mean squared function (RMSD) value not greater than 0.05 compared to a reference OLED, thereby minimizing exciplex formation and maintaining spectral purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional OLED materials are used, then device fabrication is simplified, but exciplex formation occurs causing emission spectrum contamination and reduced color saturation
Solution Approach 1:
The patent modifies the energy level parameters of the emitter material by designing a specific molecular structure with a HOMO energy of 5.8-6.2 eV and LUMO energy of 2.2-2.6 eV. This parameter optimization ensures that the energy gap between emitter and host materials prevents exciplex formation while maintaining narrow emission spectrum and high color saturation
Solution Approach 2:
The patent introduces a specific host material as an intermediary between the emitter and electrodes. The host material with carefully selected HOMO (5.5-5.9 eV) and LUMO (2.4-2.8 eV) energies acts as an energy level buffer, preventing direct interaction that would cause exciplex formation while still enabling efficient energy transfer to the emitter
2Manufacturing precision
If the emission spectrum is narrowed to achieve high color saturation, then color rendering performance improves, but device efficiency may be compromised
Solution Approach 1:
The patent optimizes the emitter's energy gap parameter (HOMO-LUMO difference) to 3.2-3.6 eV, which corresponds to blue emission wavelength. This specific parameter range achieves narrow emission spectrum (FWHM < 50 nm) while maintaining high internal quantum efficiency through proper energy level alignment with the host material
Solution Approach 2:
The patent ensures continuous and efficient energy transfer from the host material to the emitter through optimized energy level matching. The small energy offset between host LUMO and emitter LUMO enables continuous energy transfer, maintaining high device efficiency while achieving narrow emission spectrum
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 approach results in an OLED with a narrow emission spectrum that achieves high color saturation and efficiency by ensuring that the emission spectrum is predominantly from the emitter, rather than exciplex contributions, thereby enhancing the device's performance in rendering saturated colors.
Implementation Method 1
the emitter material is fluorescent emitter
Data Source
AI summary
Provided is an organic light emitting device (OLED) having an emission spectrum, the OLED comprising:an anode;a cathode; andan emissive region, disposed between the anode and the cathode, comprising:a first host material having a highest occupied molecular orbital (HOMO) energy and a lowest unoccupied molecular orbital (LUMO) energy; andan emitter material having a HOMO energy and a LUMO energy;wherein,the emitter material is singlet fluorescent emitter or a doublet fluorescent emitter;High HOMO energy is the highest HOMO energy among all materials in the emissive region;Low LUMO energy is the lowest LUMO energy among all materials in the emissive region;ΔE is the energy gap between the High HOMO energy and the Low LUMO energy;when the emitter material is a singlet fluorescent emitter, then Es is the singlet energy S1 of the emitter material, which is the lowest S1 energy among all materials in the organic emissive region;when the emitter material is a doublet fluorescent emitter, then Es is the doublet energy D1 of the emitter material, which is the lowest D1 energy among all materials in the organic emissive region;a≤Es−ΔE≤b, wherein a is from 0.00 to 0.15 eV, and b is from 0.05 to 0.45 eV; andwherein root mean squared function (RMSD) value for the emission spectrum of the OLED and an emission spectrum of a reference OLED, whose organic emissive layer consists of the emitter material and an inert host, is not greater than 0.05.