Tetradentate Pt(Ⅱ) Complexes for Spectrum-Stable Deep-Blue and White Electroluminescence

摘要

A new class of tetradentate Pt(II) complexes, Pt(pzpyOczpy-iPr) and Pt(pzpyOczpy-mesi), enabling fabrication of deep-blue and white phosphorescent devices, is successfully synthesized and fully characterized. Their photoluminescent quantum yields in dichloromethane are over 90% with short decay lifetimes less than 4.0 mu s. Under low doping concentration, the emission is governed by ligand-centered triplet transition state ((LC)-L-3,(3)pi(cz)*-pi(cz)) on carbazole group, rendering narrow blue emission with full width at half-maximum (FWHM) less than 45 nm. When increasing the doping concentration, expanded monomeric and excimeric emissions are demonstrable, displaying broad white emission with FWHM up to 152 nm. Devices fabricated with 2 wt% dopant in DPEPO host achieve a maximum external quantum efficiency (EQE(max)) of 17.2% with CIE coordinates of (0.14, 0.15). Otherwise, devices with 50 wt% dopant in mCPCN afford broad white emission with EQE(max)of 18.0% and maximum power efficiency of 60.2 lm W-1. More importantly, the concentration-dependent electroluminescence provides superior stable color under a wide range of current density, revealing a spectrum-stable emission derived from highly admixed substates in T-1.