Nowadays, organic light-emitting diodes (OLEDs) have been commercialized and shown to be successful in the market, due to their unique advantages such as self-luminance, low driving voltage, wide color gamut, wide viewing angle, ultra-thin structure, and so on. However, there are still some threatening tasks that restrict their progress. This talk will present an advance in the development of new emissive materials for OLEDs. Fluorescent organic molecules with excited-state intramolecular proton transfer (ESIPT) features have received considerable attention in recent years because of their unique photophysical properties related to large Stokes-shifted fluorescence emission. ESIPT fluorophores as light-emitting materials for OLEDs would make a perfect counterpart since the difference between positions of absorption and emission peaks, unlike most organic fluorophores, can help to avoid unwanted self-reabsorption of the emitted light, leading to improved electroluminescence and efficiency. For example, a series of ESIPT–aggregate-induced emission (AIE) solid-state fluorophores as self-absorption-free emitters will be presented. These ESIPT–AIE fluorophores exhibit high thermal and electrochemical stabilities with decent hole mobilities and are successfully utilized as emitters in OLEDs, which achieved moderate-to-good EL performances. If time is available, other types of organic emissive fluorophores will be presented, including hybridized local and charge-transfer (HLCT) and thermally activated delayed fluorescence (TADF) materials.

Most metal-organic frameworks (MOFs) lack charge mobility, which is crucial for realizing their use in optoelectronic applications. In this talk, the design of a fluorescence MOF using triarylamine-based ligands (Zr-NBP) as the lone pair electron spacer to enhance the hole mobility in the MOF while maintaining its luminescent properties will be also presented. Zr-NBP has strong fluorescence with a good hole mobility of 1.05 x 10−6 cm2 V−1 s−1, which is comparable to organic materials used in optoelectronic devices. We also employed a Zr-NBP nanofilm in the pure phase as both a non-doped emissive layer and a hole-transporting layer within OLEDs. The obtained device produced a bright green light with a low turn-on voltage.

Keywords: Organic light-emitting diode (OLED), Fluorescent molecule, Excited-state intramolecular proton transfer (ESIPT), Aggregate-induced emission (AIE), Metal-organic framework (MOF). 

Vinich Promarak received a D.Phil. in Organic Chemistry from the University of Oxford, UK. He is currently a Professor at Vidyasirimedhi Institute of Science and Technology (VISTEC), Thailand. He has authored more than 250 peer-reviewed papers with total citations of >8200 and H-index of 45. His current research interests involve “High-Tech” organic materials that can be used in optoelectronic devices i.e. organic light-emitting diode, perovskite/dye-sensitized solar cells, bulk heterojunction solar cell, sensor, luminescent solar concentrator. He was presented with many awards including Distinguished Research Professor Grant 2022, Thailand’s Outstanding Scientist Award 2021, CST High Impact Chemist Award 2017, TRF Senior Research Scholar 2017, Outstanding National Researcher Award (Chemical and Pharmaceutical Science) 2016, and Thailand’s Young Scientist Award 2007.