OLED Emissive Region Sensitizer Energy Transfer Near-Infrared
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Solution Overview
Problem
Conventional OLEDs face challenges in achieving high photoluminescence quantum yield (PLQY) due to limitations in energy transfer from triplet states to singlet states, particularly in the near-infrared region where spin-forbidden transitions lead to low radiative rates.
Innovation Solution
The use of a compound S1 as an organometallic sensitizer that transfers energy to compound A1, an acceptor and emitter with an emission onset greater than 750 nm, within the emissive region of an OLED. This configuration enhances the PLQY by optimizing energy transfer and spectral overlap between the sensitizer and acceptor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional OLED materials are used in the near-infrared region, then the device structure remains simple, but the photoluminescence quantum yield is low due to spin-forbidden transitions
Solution Approach 1:
The patent introduces a triplet sensitizer as an intermediary substance between the exciton source and the final emitter. This sensitizer accepts triplet excitons and transfers energy to the emitter molecule, enabling efficient near-infrared emission while bypassing spin-forbidden transitions. The sensitizer acts as a mediator that converts non-radiative triplet states into usable energy for radiative emission.
Solution Approach 2:
The emissive region is designed as a composite system containing both a triplet sensitizer and an emitter molecule with specific energy level alignments. This composite approach combines materials with complementary properties: the sensitizer provides efficient triplet state management while the emitter delivers the desired near-infrared emission, achieving high photoluminescence quantum yield through their synergistic interaction.
2Productivity
If energy transfer from triplet states to singlet states is attempted in conventional OLEDs, then the emission process is simplified, but the transfer efficiency is low due to spin conservation rules
Solution Approach 1:
The triplet sensitizer serves as an intermediary that facilitates energy transfer by first accepting triplet excitons and then transferring singlet energy to the emitter. This two-step process bypasses the inefficient direct triplet-to-singlet transfer, achieving high energy transfer efficiency while minimizing non-radiative losses through proper energy level matching between sensitizer and emitter.
Solution Approach 2:
The patent optimizes key parameters including the energy gap between sensitizer triplet state and emitter singlet state, ensuring it falls within the optimal range for efficient energy transfer. By carefully selecting materials with appropriate HOMO-LUMO gaps and triplet energy levels, the system achieves high productivity while minimizing energy loss through non-radiative pathways.
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 implementation of compound S1 and A1 in the OLED emissive region significantly increases the PLQY, exceeding that of an equivalent region without compound A1, thereby improving the overall efficiency and performance of the OLED.
Implementation Method 1
compound S1 is an organometallic sensitizer that transfers energy to the compound A1
Implementation Method 2
the compound A1 is an acceptor that is an emitter; the compound A1 has an emission onset greater than 750 nm
Data Source
AI summary
An organic light emitting device (OLED) comprising, sequentially an anode; a hole transporting layer; an emissive region; an electron transporting layer; and a cathode is provided. In the OLED, the emissive region comprises a compound S1 and a compound A1, where the compound S1 is an organometallic sensitizer that transfers energy to the compound A1, and the compound A1 is an acceptor that is an emitter; the compound A1 has an emission onset greater than 750 nm; and the PLQY of the emissive region comprising both compound S1 and compound A1 is greater than the PLQY of an equivalent emissive region without compound A1. Consumer products containing the OLED are also provided.