Iridium-based emitters containing pendant triphenylene moieties for bluish-green OLEDs with improved efficiency upon thermal annealing

Abstract

Two new cyclometalated iridium complexes with non-conjugated triphenylene moieties attached to the ancillary ligand, namely YF3 and YF4, are reported. Both iridium complexes presented intense bluish-green emission both in solution (Φ_PL ∼ 0.37–0.5) and in the solid state. A high hole mobility of 0.001 cm² V⁻¹ s⁻¹ was obtained for YF4 annealed film, evidenced by the space-charge-limited-current method. This result is among the highest hole mobilities reported for a cyclometalated iridium complex. Organic light-emitting diodes employing these iridium complexes as dopants were fabricated. The influence of the annealing temperature of both the emitting layer and the host matrix on the device performance was explored. Interestingly, YF4-based device with an annealing temperature of 60 °C shows the best performance with a maximum current efficiency of 15.6 cd A⁻¹ and an external quantum efficiency of 6.8% compared to 1.5 cd A⁻¹ and 0.8% for the non-annealed device.