850 nm Pure Near-Infrared Emitting Iridium Complex for Solution-processed Organic Light-Emitting Diodes
High-performance pure near-infrared organic light-emitting materials and devices with full emission over 700 nm are still rare, though urgently needed. Iridium(III) complexes have been proven to be an important class of NIR emitters. Herein, we report a new NIR homoleptic Ir(III) complex, tris[1,4-di(5-n-octylthiophen-2-yl)benzo[g]phthalazine] iridium(III) (Ir(dotbpa)3), with full emission beyond 700 nm and Iridium mass content as low as 10 wt%. Thanks to the introduction of flexible n-octyl groups, Ir(dotbpa)3 shows greatly improved solubility and excellent solution-processability in comparison with its counterpart Ir(dtbpa)3. By employing a multifunctional host, solution-processed NIR-OLEDs were fabricated with a simple structure of only three organic layers and demonstrated pure NIR emission starting from 725 nm and peaking at 850 nm with maximum external quantum efficiency of 0.17%, which is the first example to achieve pure NIR-OLEDs based on Ir(III) emitters.