Sterically Hindered OLED Emitters for Blue Lifetime and Solution Processing
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Solution Overview
Problem
Existing organic electroluminescent devices (OLEDs) face challenges in achieving improved performance in terms of lifetime, efficiency, operating voltage, and color purity, particularly for blue-emitting devices, with a need for better fluorescent emitters that can be processed easily from solution and provide high efficiency, long lifetime, and suitable color coordinates.
Innovation Solution
Development of sterically hindered fluorescent emitters, such as compounds of formula (1), which can be used in hyperfluorescent or hyperphosphorescent systems, offering prompt fluorescence and delayed fluorescence, and are suitable for both vacuum processing and solution processing, enhancing device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fluorescent emitters are used in OLEDs, then the device can be manufactured with standard processes, but the lifetime and efficiency of blue-emitting devices remain insufficient
Solution Approach 1:
The patent modifies molecular parameters of fluorescent emitters by introducing sterically hindered groups (tert-butyl, adamantyl) and specific heteroatom configurations to optimize lifetime and efficiency while maintaining solution processability. The compounds achieve lifetimes exceeding 1000 hours at 100 cd/m² with external quantum efficiencies above 20% through careful structural parameter optimization
Solution Approach 2:
The patent develops composite fluorescent emitter molecules combining multiple functional units (triphenylamine, dibenzofuran, indenodibenzofuran) with specific spatial arrangements. These composite structures integrate charge transport, exciton management, and emission functions into single molecules, achieving both improved device performance and solution processability
2Measurement precision
If blue-emitting OLEDs are optimized for color purity, then the color coordinates improve, but the lifetime and efficiency deteriorate
Solution Approach 1:
The patent introduces specific local structural features (sterically hindered groups at positions 2 and 7 of the dibenzofuran core) that locally manage exciton dynamics and energy transfer. These localized structural modifications create favorable microenvironments for exciton management, achieving both color purity (Commission Internationale de l'Éclairage 1931 x < 0.15) and extended device lifetime
Solution Approach 2:
The sterically hindered fluorescent emitter compounds act as intermediaries between the electric field and light emission. Their specific molecular structures mediate energy transfer from charge carriers to emissive states while managing triplet excitons, achieving high external quantum efficiencies (above 20%) and color purity simultaneously
3Productivity
If high efficiency emitters are developed, then the light output improves, but the processing complexity increases
Solution Approach 1:
The sterically hindered fluorescent emitter compounds possess inherent properties (appropriate solubility, thermal stability, and molecular packing characteristics) that enable them to self-organize during solution processing. The molecules' built-in structural features facilitate spontaneous formation of functional thin films without requiring complex processing equipment or multi-step procedures, achieving high efficiency through simple spin-coating or inkjet printing
Solution Approach 2:
The patent develops universal fluorescent emitter compounds that can be processed through multiple methods (solution processing, vacuum deposition) and used in various OLED architectures. The compounds exhibit broad applicability across different device configurations while maintaining high efficiency, reducing the need for device-specific material optimization
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 compounds of formula (1) improve OLED performance by providing high efficiency, long lifetime, and suitable color coordinates, especially in blue emission, while allowing for easy processing from solution, addressing the limitations of existing technologies.
Implementation Method 1
The compounds according to the invention can be employed as fluorescent emitters or TADF (thermally activated delayed fluorescence) emitters
Implementation Method 2
TADF materials are, in general, organic materials in which the energy gap between the lowest triplet state T1 and the first excited singlet state S1 is sufficiently small so that the S1 state is thermally accessible from the T1 state
Data Source
AI summary
The present invention relates to compounds of the formula (1) which are suitable for use in electronic devices, in particular organic electroluminescent devices, and to electronic devices which comprise these compounds.