Near-Infrared Polymer Light-Emitting Diodes with High Efficiency and Low Efficiency Roll-off by Using Solution-Processed Iridium(III) Phosphors

Two deep-red/near-infrared (NIR) iridium phosphors, (fldpqx)(2)Ir-(acac) and (thdpqx)(2)Ir(acac), were rationally designed and synthesized considering the emission wavelength, emission efficiency, and solubility. In optimized solution-processed phosphorescent polymer light-emitting devices, the (fldpqx)(2)Ir(acac)-based device achieved a maximum external quantum efficiency of 5.7% with the emission peak at 690 nm, while the (thdpqx)(2)Ir(acac)-based device achieved a maximum external quantum efficiency of 3.4% with the emission peak at 702 nm, which are comparable to the highest values ever reported for solution-processable NIR emitters. Moreover, these devices merely experienced low efficiency roll-off at high current densities.