OLED Emissive Region Using Sensitizer-Acceptor Energy Transfer
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Solution Overview
Problem
Current OLED technologies face challenges in achieving efficient energy harvesting of singlet and triplet excitons, which limits their performance in producing saturated colors and internal quantum efficiency.
Innovation Solution
The use of a combination of phosphorescent or TADF emitters as sensitizers and multiple acceptor emitters in OLED devices, where compounds S1 and S2 act as sensitizers transferring energy to compounds A1 and A2, respectively, allowing for efficient energy transfer and emission, even at room temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional OLED materials are used, then device structure is simple, but energy harvesting efficiency of singlet and triplet excitons is limited
Solution Approach 1:
The patent combines phosphorescent or TADF emitters with multiple fluorescent acceptor emitters in a single emissive region, creating a multi-component system that harvests both singlet and triplet excitons. This merging of different emitter types enables efficient energy utilization while maintaining a relatively simple overall device structure.
Solution Approach 2:
The emissive region uses composite material systems where phosphorescent or TADF sensitizers work in conjunction with fluorescent acceptor emitters. This composite approach allows the system to leverage the long transient times of phosphorescent/TADF materials for efficient triplet harvesting while achieving the short transient times and high efficiency of fluorescent materials.
2Loss of energy
If phosphorescent emitters are used to harvest triplet excitons, then energy harvesting efficiency improves, but transient time increases
Solution Approach 1:
The patent uses phosphorescent or TADF emitters as intermediary sensitizers that absorb excitons (both singlet and triplet) and then transfer energy to fluorescent acceptor emitters. This intermediary mechanism allows the system to benefit from the efficient triplet harvesting capability of phosphorescent/TADF materials while the fluorescent acceptors provide the desired short transient times for high-speed operation.
Solution Approach 2:
The system changes the transient time parameter by combining materials with different transient characteristics. The phosphorescent or TADF sensitizers have long transient times enabling efficient energy capture, while the fluorescent acceptors have short transient times enabling fast emission. The energy transfer between these components results in an overall system with optimized transient time characteristics.
3Illumination intensity
If white OLED with absorption filters is used to produce saturated colors, then color saturation improves, but energy efficiency decreases
Solution Approach 1:
The patent segments the emissive region into multiple components, each responsible for emitting specific colors (e.g., red, green, blue acceptors). This segmentation eliminates the need for absorption filters by directly emitting saturated colors from different acceptor emitters, thereby improving energy efficiency while maintaining color saturation.
Solution Approach 2:
The system achieves color saturation through the intrinsic emission characteristics of different acceptor emitters rather than filtering white light. Each acceptor emitter is selected to emit at specific wavelengths corresponding to saturated colors, and the phosphorescent or TADF sensitizers transfer energy to these acceptors, enabling direct emission of saturated colors with high energy efficiency.
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 enables OLEDs to harvest a majority of electrogenerated excitons, achieving high internal quantum efficiency and producing predominantly from acceptor emitters with short transient times, similar to fluorescent systems.
Implementation Method 1
The singlet and triplet excitons which are electrogenerated within an OLED device can be harvested by the phosphorescent emitter or TADF emitter as a sensitizer and can subsequently energy transfer to the TADF emitter or fluorescent emitters that are acting as acceptors
Implementation Method 2
OLEDs make use of thin organic films that emit light when voltage is applied across the device
Data Source
AI summary
Provided is an organic light emitting device (OLED) comprising: an anode; a cathode; and an emissive region disposed between the anode and the cathode; wherein the emissive region comprises: a compound S1; a compound A1; a compound S2; and a compound A2; wherein the compound S1 is a sensitizer that transfers energy to the compound A1; and the compound S2 is a sensitizer that transfers energy to the compound A2; wherein each of the compound A1 and A2 is independently an acceptor that is an emitter; wherein the compound S1 can be same or different from the compound S2; wherein the compound A1 can be same or different from the compound A2; and wherein at least one of the following conditions is true: (1) the compound S1 is different from the compound S2; (2) the compound A1 is different from the compound A2. Also provided are related formulations, related premixed co-evaporation sources, related consumer products and related method of making those OLED devices.