High-performance solution-deposited ambipolar Ir(iii) complex phosphors with aggregation-induced phosphorescence enhancement behavior based on an N–PO resonant variation skeleton

Abstract

Ir(III) complex phosphors with both ambipolar feature and aggregation-induced phosphorescence enhancement (AIPE) property are promising for furnishing high electroluminescent performance in solution-deposited phosphorescent organic light-emitting diodes. However, the molecular design is really challenging. To address this issue, we successfully designed and synthesized two ambipolar carbazole-based Ir(III) complexes Ir2CzNPO and Ir3CzNPO with AIPE behavior based on the N–PO resonant variation skeleton. Ir2CzNPO and Ir3CzNPO can exhibit high PLQYs of 0.76 and 0.98, respectively, in doped TCTA films. Furthermore, the PL intensity of Ir2CzNPO and Ir3CzNPO can be enhanced by around 6.1 and 3.7 folds, respectively, with the percentage of water volume increasing in the THF/water solvent system, indicating their AIPE behavior. The CV results demonstrate the ambipolar feature of Ir2CzNPO and Ir3CzNPO. Benefiting from the high PLQY, ambipolar feature and AIPE property, solution-deposited device B2 based on Ir3CzNPO can show a low turn-on voltage of 3.0 V and achieve a maximum external quantum efficiency (η_ext) of 26.9%, a maximum current efficiency (η_L) of 69.2 cd A⁻¹ and a maximum power efficiency (η_P) of 59.3 lm W⁻¹. This research definitely paves a new and promising way for designing high-performance ambipolar phosphorescent materials with an AIPE feature for solution-deposited organic light-emitting diodes.