Planar Pt(II) Complexes for Low-Doped Excimer-Based Phosphorescent Organic Light-Emitting Diodes

Two novel Pt(II) complexes of type Pt[NC-O-C & PRIME;N & PRIME;],Pt(pzpyOppz-A) and Pt(pzpyOppz-B), were developed for excimer-basedemissions. NC and N & PRIME;C & PRIME; are the motifsof substituted pyrazolyl-pyridyl (pzpy) and phenyl-pyrazolyl (ppz),respectively. The complexes can readily form dimers in a solid matrix,resulting in an excimer-based emission with high photoluminescenceefficiency. By utilizing dual emission bands corresponding to themonomer and excimer, efficient phosphorescent organic light-emittingdiodes (PhOLEDs) with a broad spectral emission were fabricated. Thedevice employing Pt(pzpyOppz-A) achieves a broad yellowish-white emissionwith a full width at half-maximum of 152 nm at 3 wt % concentrationand maximum external quantum efficiency (EQE), power efficiency (PE),and current efficiency (CE) of 20.7%, 43.9 Lm W-1, and 60.1 cd A(-1), respectively, at a 5 wt % concentration.The device with 40 wt % Pt(pzpyOppz-B) therein exhibits an exclusiveexcimer-based emission with the maximum EQE, PE, and CE of 25.5%,55.5 Lm W-1, and 62.3 cd A(-1),respectively. This work shows the molecular art of the Pt(II) complexfor highly performable phosphorescent devices via utilizing the in-situ-formeddimer in a simplified architecture.