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, 38 nm), a shallow highest occupied molecular orbital (HOMO) energy level, and short radiative lifetime of 0.66 μs is designed and synthesized. The best device based on a new Ir(III) complex yields record-high radiant emittance (> 5 mW cm−2) at low voltage (6 V), low external quantum efficiency (EQE) roll-off, low driving voltage (2.5–6 V), and stable operational lifetime for biomedical application with an emission peak wavelength of 696 nm. 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.