Design and Synthesis of Red to Near-Infrared (Nir) Multi-Resonance Materials for Efficient Luminescent Applications

Organic electronics have gained immense attention, since their device properties can be easily tuned by structural modification of organic functional molecules and by interfacial device engineering. Understanding the intrinsic properties of organic functional materials is the key to high-performance organic electronics. Thermally activated delayed fluorescent (TADF) material is an emerging class of metal-free luminescent materials for organic electronics and biological applications. Nowadays, red, green and blue (RGB) TADF materials have achieved excellent efficiencies and stabilities in organic light-emitting diodes (OLEDs); however, broadband emission spectra of donoracceptor- type (DA-type) TADF materials result in relatively low color purity when compared to other luminescent materials, which render DA-type TADF material less competitive. To achieve ultra-high-definition display, the color gamut of RGB color has to be advanced to BT. 2020 standard, in which narrow electroluminescent spectra are needed. Pure organic multi-resonance (MR) materials that possess narrow emissions are considered to be the next-generation luminescent materials. Nonetheless, MR materials reported in the literature always emit at high energy level (<500 nm), while reports on emissions at low energy, especially for red to deep-red color, are limited. Most importantly, NIR MR materials are rarely reported in any literature. Meanwhile, red to deep-red MR materials reported in the literature always exhibit moderate photoluminescence quantum yield (PLQY) and slow spin-flipping process, that is delayed lifetimes being in the millisecond range, which leads to poor device performance in organic electronics. Undeniably, red and NIR emissive materials are very useful for biological applications. As a result, the research and development of efficient MR materials with emissions at longer wavelengths and high PLQYs is highly demanded. This proposed project seeks to design and synthesize efficient red to NIR MR materials; particularly in an attempt 1) to expand the molecular library of boron-nitrogen-type MR materials with emissions in red/NIR region ; 2) to investigate structure-photophysics relationship of MR-TADF materials and to provide insight and designing principle of MR-TADF materials with efficient reverse intersystem crossing; 3) to demonstrate highly efficient red/NIR OLEDs. The successful implementation of this project will lay the foundation for future development of red and NIR MR materials not only in organic electronics, but also in biological applications.