Tailoring optoelectronic properties of benzimidazole-based iridium(Ⅲ) complexes through rational isomer engineering

Abstract

Iridium(Ⅲ) (Ir(Ⅲ)) complexes are widely used in commercial organic light-emitting diodes due to their excellent luminescent property. In the development of Ir(Ⅲ) complexes, the construction of isomers becomes a simple and effective path to regulate the photophysical and electronic properties. Two new isomeric bis-cyclometalated benzimidazole-based Ir(Ⅲ) complexes bis[2-(naphthalen-1-yl)-1-phenyl-1H-benzo[d]imidazole]iridium-2-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine (Ir-1) and bis[2-(naphthalen-2-yl)-1-phenyl-1H-benzo[d]imidazole]iridium-2-(3-(trifluoromethyl)-1H-1,2,4-triazol-5-yl)pyridine (Ir-2) were designed and synthesized. Ir-1 and Ir-2 exhibited significantly different photophysical properties and thermal stability, such as emission color, photoluminescence quantum yields (PLQYs), the distribution of energy level and so on. The vacuum-deposited devices with Ir-1 and Ir-2 as dopant emitters following the preliminary structure of ITO/TAPC (20 nm)/CBP: Ir(III) complexes (30 nm)/TPBi (50 nm)/Liq (2 nm)/Al were also fabricated and investigated. The Ir-2-doped device exhibited better electrophosphorescent performances of 10900 cd m-2, 52.6 cd A-1, 42.3 lm W-1 and 16.3% together with good color stability.