Curcuminoid Derivatives with a Donor-Acceptor-Donor Architecture: an Outstanding Platform for Highly-Efficient Near-Infrared Electroluminescence and Amplified Spontaneous Emission

The development of high-efficiency near-infrared (NIR) emitters for organic light-emitting diodes (OLEDs) and organic semiconductor lasers has become an important target in organic photonics. Herein, it is demonstrated that donor-acceptor-donor borondifluoride curcuminoid derivatives represent a versatile and simple platform for the molecular engineering of high-efficiency NIR emitters combining thermally-activated delayed fluorescence (TADF) with excellent electroluminescence properties and amplified spontaneous emission (ASE) activity. A series of donor-acceptor-donor curcuminoid compounds containing triphenylamino-substituents for the donor side groups and various acceptor units in the meso position were designed and synthesized. The investigation of the effects of the molecular structure on the TADF properties show that the nature of the substituents enables a fine tuning of the emission wavelengths while maintaining high photoluminescence quantum yield values. These NIR TADF dyes were used in OLEDs with an external quantum efficiency of almost 1% for a maximum emission wavelength of 797 nm. They also show a low threshold tuneable amplified spontaneous emission between 725 and 900 nm. Overall, this study provides new essential insights to rationalize the TADF activity of this family of NIR emitters and offers important prospects for designing the next generation of NIR TADF-OLEDs and organic semiconductor laser materials.