Pt(II) phosphors with dual 1,6-naphthyridin-5-yl pyrazolate chelates and non-doped organic light emitting diodes

Abstract

Pt(II) metal complexes are known for having strong intermolecular Pt & ctdot;Pt interaction in the condensed phases, to which the associated metal-metal-to-ligand charge transfer (MMLCT) transition characteristics allowed the effective generation of long-wavelength emission down to the red and near-infrared region. To expand the scope of the designs, we synthesized three homoleptic Pt(II) complexes Pt(a), Pt(b), and Pt(c) using chelating naphthyridinyl pyrazolates, which exhibited efficient emission peaks centered at 681, 690 and 723 nm as the vacuum deposited thin film. Upon fabrication of OLED devices, device Pt(b) achieved emission centered at 676 nm, maximum EQE of 25.6% with suppressed efficiency roll-off. Furthermore, device Pt(c) exhibited emission peaking at 710 nm and a slightly inferior but still remarkable max. EQE of 17.8%, paving a basis for further exploration of these self-aggregated Pt(II) metal phosphors and optimization of relevant NIR OLED devices.