Efficient near-infrared (NIR) polymer light-emitting diodes (PLEDs) based on heteroleptic iridium(III) complexes with post-modification effects of intramolecular hydrogen bonding or BF2-chelation

In heteroleptic iridium(III)-complexes capable of near-infrared (NIR) emitting, elaboration of their ancillary ligands is under-explored. In this study, through OH-modification at the 3-position of the picolinato (pic) ancillary ligand, we report two new complexes [Ir(iqbt)(2)(hpa)] (1; Hiqbt = 1-(benzo[b]-thiophen-2-yl)-isoquinoline; hpa = 3-hydroxypicolinate) with intramolecular hydrogen bonding and [Ir(iqbt)(2)(BF(2)hpa)] (2) with further BF2-chelation, exhibiting desirable NIR luminescent properties (lambda(em) = 700 nm with a shoulder at 760 nm, lifetime tau = 2.13 mu s and quantum yield Phi(PL) = 0.13 for 1 versus lambda(em) = 692 nm with a shoulder at 756 nm, lifetime tau = 0.76 ps and quantum yield Phi(PL) = 0.08 for 2) in their respective solutions at RT. Moreover, two series of solution-processed NIR polymer light-emitting diodes (PLEDs-I-II) are fabricated from these two complexes, either in the presence or absence of a TmPyPB-assisted (TmPyPB = 1,3,5-tri[(3-pyridyl)-phen-3-yl]benzene) carrier balance, where a superior performance (eta(max)(EQE) = 2.22% and almost negligible efficiency-roll-off) is obtained for complex-1-doped NIR-PLED-II, with particular respect to facilitated electron transport.