Thienothiophenyl-Isoquinoline Iridium Complex-Based Deep Red to Near-Infrared Organic Light-Emitting Diodes with Low Driving Voltage and High Radiant Emittance for Practical Biomedical Applications

Abstract

It is extremely rare that near-infrared organic light-emitting diodes (NIR OLEDs) have been actually applied to various fields such as sensors, night-vision displays, or phototherapy owing to device reliability and stability. Therefore, developing a novel deep red to NIR (DR/NIR) emitter for the high-performance DR/NIR OLED has become a prominent research area. Herein, a novel thienothiophene-isoquinoline-based Ir(III) complex DR/NIR emitter with narrow full width half maximum (FWHM, 38nm), a shallow highest occupied molecular orbital (HOMO) energy level, and short radiative lifetime of 0.66 mu s is designed and synthesized. The best device based on a new Ir(III) complex yields record-high radiant emittance (> 5mWcm(-2)) at low voltage (6V), low external quantum efficiency (EQE) roll-off, low driving voltage (2.5-6V), and stable operational lifetime for biomedical application with an emission peak wavelength of 696nm. From all perspectives, this is notably an outstanding performance among other reported Ir(III)-based DR/NIR OLEDs. Moreover, DR/NIR OLEDs are applied to the biomedical field and an in vitro experiment shows an increase in cell proliferation effect of up to 24% under diverse conditions.