Blue OLED Emission Layer with Triplet-Triplet Annihilation Upconversion
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Solution Overview
Problem
Blue organic light-emitting diodes (OLEDs) suffer from lower efficiency and shorter lifetime due to exciton-polaron annihilation, which is also a challenge for thermally activated delayed fluorescence (TADF) devices, as the long triplet exciton lifetime leads to energy transfer and bonding breakage in organic materials.
Innovation Solution
Incorporating a triplet-triplet annihilation (TTA) material and a donor material in the emission layer, with a sensitizer that has specific singlet and triplet energy levels, allowing for triplet-triplet annihilation up-conversion (TTAUC) to generate blue light, thereby reducing exciton-polaron annihilation and enhancing the efficiency and lifetime of blue and white OLEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of stationary object
If blue OLED uses conventional fluorescence or phosphorescence system, then device can emit blue light, but exciton lifetime is long leading to exciton-polaron annihilation and short device lifetime
Solution Approach 1:
The patent changes the energy level parameters of the emission layer materials. Specifically, it uses a TTA material with high triplet energy (2.8 eV) and a donor material with higher triplet energy (3.3 eV), creating an energy gradient that enables rapid triplet-triplet annihilation and reduces exciton lifetime from microseconds to nanoseconds, thereby preventing exciton-polaron annihilation and extending device lifetime
Solution Approach 2:
The patent introduces a donor material as an intermediary between the anode and the TTA material. This donor material acts as a mediator that facilitates efficient energy transfer to the TTA material while maintaining short exciton lifetime, thus enabling both long device lifetime and high efficiency through the intermediary's specific energy level configuration
2Productivity
If blue OLED uses TADF system with long triplet exciton lifetime (1-10 μs), then device can operate, but hot exciton-polaron annihilation reaction is inevitable causing energy loss
Solution Approach 1:
The patent changes the energy level parameters by selecting a TTA material with triplet energy of 2.8 eV and a donor material with triplet energy of 3.3 eV. This parameter configuration enables rapid triplet-triplet annihilation that converts triplet excitons to singlet excitons with short lifetime, thereby reducing hot exciton-polaron annihilation and improving power efficiency to above 20%
Solution Approach 2:
The patent converts the potentially harmful long-lived triplet excitons into beneficial short-lived singlet excitons through triplet-triplet annihilation. The triplet excitons that would otherwise cause hot annihilation are transformed into singlet excitons with nanosecond lifetime that emit blue light efficiently, turning the harm of long triplet lifetime into the benefit of efficient blue light emission
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 significantly increases power efficiency and extends the light-emitting lifetime by reducing exciton-polaron annihilation, enabling the production of high-efficiency and long-lifetime blue and white OLEDs through efficient energy transfer and light mixing.
Implementation Method 1
the third triplet energy is transferred to the TTA material for sensitizing a triplet-triplet annihilation up-conversion (TTAUC), such that the first singlet energy emits a blue light
Implementation Method 2
the third triplet energy is transferred to the TTA material
Implementation Method 3
the first singlet energy emits a blue light
Implementation Method 4
the third singlet energy emits a yellow light or a yellow green light
Data Source
AI summary
An organic light-emitting diode (OLED) and a white OLED are provided. The OLED sequentially includes an anode, an emission layer, an electron transport layer, and a cathode. The emission layer includes a triplet-triplet annihilation (TTA) material and a donor material. The doubled triplet energy of the TTA material is greater than the singlet energy of the TTA material. The donor material is disposed between the anode and the TTA material and has a second singlet energy and a second triplet energy. A sensitizer is doped in the emission layer or formed between the TTA material and the donor material when a voltage is applied. The sensitizer has a third singlet energy and a third triplet energy. The third singlet energy and the third triplet energy are both smaller than the second singlet energy.