Highly efficient green phosphorescent OLEDs based on a novel iridium complex

Abstract

A new iridium(III) complex Ir(tfmppy)₂(tfmtpip) (1, tfmppy = 4-trifluoromethylphenyl-pyridine, tfmtpip = tetra(4-trifluoromethylphenyl)imidodiphosphinate) was synthesized and applied in organic light-emitting diodes (OLEDs). The devices with the structures of ITO/TAPC (1,1-bis[4-[N,N-di(p-tolyl)amino]phenyl]cyclohexane, 40 nm)/1 (x wt%): mCP (N,N′-dicarbazolyl- 3,5-benzene, 20 nm)/TmPyPB (1,3,5-tri(m-pyrid-3-yl-phenyl)benzene, 40 nm)/LiF (1 nm)/Al (100 nm) exhibited a maximum power efficiency (η_p,max) of 113.23 lm W⁻¹ and a maximum current efficiency (η_c,max) of 115.39 cd A⁻¹ (0.01342 mA cm²) at the doping level of 5 wt%, which is among the best performances for Ir(III) complex based OLEDs in the green-light-emitting region. Compared with our former work, the excellent device efficiencies are due to the use of TmPyPB as the electron-transporting/hole-blocking layer which has a relatively higher electron mobility than that of TPBi (2,2′,2′′-(1,3,5-benzinetriyl)-tris(1-phenyl-1-H-benzimidazole)) and the introduction of the –CF₃ moiety to the Ir(III) complex, which can increase the electron mobility of the complex. The device performances proved that the complex has potential applications as an efficient green emitter in OLEDs.