Efficient and low-efficiency-roll-off near-infrared (NIR) polymer light-emitting diodes (PLEDs) based on an asymmetric binuclear iridium(III)-complex

Abstract

Abstract Through the replacement of the β-diketonate Hbtfa (Hbtfa=4,4,4-trifluoro-3-hydroxy-1-phenylbutanone) with the bis-β-diketonate ligand H2btp (H2btp=1,3-bis(4,4,4-trifluoro-1,3-dioxobutyl)benzene), structure converts from mononuclear [Ir(iqbt)2(btfa)] (1) (Hiqbt=1-(benzo[b]-thiophen-2-yl)-isoquinoline) to asymmetric dinuclear [(iqbt)2Ir-(btp)-Ir(iqbt)2] (2) framework toward larger molecule conjugation. Upon a significant bathochromic shift into the restrictive near-infrared (NIR) regime (λem=722 nm for complex 2 and 698 nm for complex 1), the superior phosphorescence (Φem=0.15 and τ = 1.27 μs) of complex 2 to that (Φem=0.08 and τ = 0.78 μs) of complex 1 is also approached. Moreover, within the realization of their solution-processed NIR polymer light-emitting diodes (NIR-PLEDs-I-II), complex-2-doped NIR-PLED-II in the presence of TmPyPB-assisted (TmPyPB=1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene) carrier balance, exhibits the attractive electroluminescent (EL) performance with both ηEQEmax= 3.11% and almost negligible efficiency-roll-off.