OLED Sensitizer Layer Triplet-Triplet Annihilation Upconversion
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Solution Overview
Problem
Conventional organic light-emitting diodes (OLEDs) face challenges in extending the lifetime of blue OLEDs due to rapid degradation caused by high energy blue photons and inefficiency in utilizing triplet excitons, which account for 75% of excited states, resulting in wasted energy.
Innovation Solution
An organic light-emitting diode structure incorporating a luminescent layer and a sensitizer layer, where the sensitizer layer's triplet state is positioned between the luminescent layer's singlet and triplet states, facilitating triplet-triplet annihilation upconversion, allowing the conversion of triplet energy into emitted light, thereby extending the OLED's lifetime and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If triplet excitons are utilized in conventional fluorescent OLEDs, then light emission occurs, but triplet excitons cannot return to ground state with photon emission resulting in energy waste
Solution Approach 1:
The patent introduces a sensitizer layer as an intermediary between the charge injection layer and luminescent layer. This sensitizer layer absorbs energy from triplet excitons and transfers it to the luminescent layer, enabling triplet excitons to contribute to light emission. The sensitizer layer acts as a mediator that converts non-emissive triplet energy into useful photons, resolving the energy waste problem in conventional fluorescent OLEDs.
Solution Approach 2:
The patent changes the energy level parameters of the OLED structure by introducing a sensitizer layer with specific triplet state energy levels positioned between the luminescent singlet and triplet states. This parameter adjustment enables efficient energy transfer from triplet excitons to the luminescent layer, converting previously wasted triplet energy into light emission and improving overall device efficiency.
2Power
If blue photons are emitted to achieve high energy output, then illumination efficiency is improved, but rapid degradation occurs reducing device lifetime
Solution Approach 1:
The patent converts the harmful high-energy blue photons that cause degradation into a beneficial mechanism by using triplet-triplet annihilation upconversion. Instead of directly emitting high-energy blue photons that break molecular bonds, the system uses lower-energy triplet excitons that are converted into blue light through the upconversion process. This indirect pathway maintains the desired blue emission while avoiding the harmful effects of direct high-energy photon generation.
3Use of energy by moving object
If singlet excitons are used for light emission, then photons are emitted, but only 25% of excited excitons contribute to light emission
Solution Approach 1:
The sensitizer layer serves as an intermediary that captures triplet exciton energy and transfers it to the luminescent layer. This mediator enables triplet excitons, which normally cannot emit photons, to contribute to light emission through energy transfer, thereby increasing the overall utilization efficiency of excitons in the OLED device.
Solution Approach 2:
By adjusting the energy level parameters and introducing the sensitizer layer with appropriate triplet state energy, the patent enables efficient energy transfer from triplet to singlet states. This parameter optimization allows both singlet and triplet excitons to contribute to light emission, significantly improving exciton utilization efficiency from 25% to potentially 62.5% or higher.
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
The solution effectively harnesses triplet energy to enhance the external quantum efficiency and extend the lifespan of OLEDs by converting previously wasted energy into emitted light, outperforming conventional OLEDs in terms of illumination efficiency and longevity.
Implementation Method 1
The molecules of the sensitizer layer at the sensitizer layer triplet layer transfers energy to the molecules of the luminescent layer at the luminescent-layer triplet state and triggers triplet-triplet annihilation upconversion in the luminescent layer such that the luminescent layer emits light of a first color
Implementation Method 2
light is emitted when singlet excitons return to the ground state
Data Source
AI summary
An organic light-emitting diode including an anode, a cathode, and a luminescent layered structure is provided. The luminescent layered structure is disposed between the anode and the cathode. The luminescent layered structure has a luminescent layer and a sensitizer layer. The luminescent layer has a luminescent-layer ground state, a luminescent-layer singlet state and a luminescent-layer triplet state, in which two times of the luminescent-layer triplet state is higher than the luminescent-layer singlet state. The sensitizer layer has a sensitizer-layer triplet state, which is between the luminescent-layer singlet state and the luminescent-layer triplet state. The molecules of the sensitizer layer at the sensitizer layer triplet layer transfers energy to the molecules of the luminescent layer at the luminescent-layer triplet state and triggers triplet-triplet annihilation upconversion in the luminescent layer such that the luminescent layer emits light of a first color