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Near‐IR organic light‐emitting diodes (NIR‐OLEDs) are potential light‐sources for various sensing applications as OLEDs have unique features such as ultra‐flexibility and low‐cost fabrication. However, the low external electroluminescence (EL) quantum efficiency (EQE) of NIR‐OLEDs is a critical obstacle for potential applications. Here, we demonstrate a highly efficient NIR emitter with thermally activated delayed fluorescence (TADF) and its application to NIR‐OLEDs. The NIR‐TADF emitter, TPA‐PZTCN, has a high photoluminescence quantum yield of over 40 % with a peak wavelength at 729 nm even in a highly doped co‐deposited film. The EL peak wavelength of the NIR‐OLED is 734 nm with an EQE of 13.4 %, unprecedented among rare‐metal‐free NIR‐OLEDs in this spectral range. TPA‐PZTCN can sensitize a deeper NIR fluorophore to achieve a peak wavelength of approximately 900 nm, resulting in an EQE of over 1 % in a TADF‐sensitized NIR‐OLED with high operational device durability (LT95>600 h.). [ABSTRACT FROM AUTHOR]

The development of near‐infrared (NIR) light sources has attracted much interest due to their attractive applications, such as biosensing and light detection and ranging (LiDAR). In particular, organic semiconductor laser diodes with NIR emission are emerging as a next generation technology. However, organic NIR emitters have generally suffered from a low quantum yield, which has resulted in only a few examples of organic solid‐state NIR lasers. In this study, the authors demonstrate a highly efficient NIR emitter based on a boron difluoride curcuminoid structure, which shows a high photoluminescence (PL) quantum yield (ΦPL) at >700 nm and a high fluorescence radiative rate constant in a solid‐state film. Amplified spontaneous emission and lasing occurs at >800 nm with very low thresholds. The large redshift of the stimulated emission is attributed to the transition from the lowest excited state to the different vibrational levels of the ground state owing to the overlap between the emission and the singlet–singlet excited‐state absorption. [ABSTRACT FROM AUTHOR]