An 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 with an 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 utilizing a multifunctional host, solution-processed NIR-OLEDs were fabricated with a simple structure of only three organic layers and they demonstrated a pure NIR emission starting from 725 nm and a peak at 850 nm with the maximum external quantum efficiency of 0.17%, which makes them the first example of pure NIR-OLEDs based on Ir(III) emitters.