Highly efficient platinum-based emitters for warm white light emitting diodes

摘要

New cycloplatinated N-heterocyclic carbene (NHC) compounds with chelate diphosphines (P<^>P) as ancillary ligands, [Pt(R-C<^>C*)(P<^>P)]PF6 (R-C = Naph, P<^>P = dppm 1A, dppe 2A, dppbz 3A; R = CO2Et, P<^>P = dppm 1B, dppe 2B, dppbz 3B), have been prepared. Their photophysical properties have been extensively studied and supported by the time-dependent-density functional theory (TD-DFT). These compounds show a great thermal stability and a very efficient blue (CO2Et-C<^>C*) or cyan (Naph<^>C*) emission in PMMA films (5 wt%), with photoluminescence quantum yield (PLQY) ranging from 53% to 95%. In the solid state, the emission of the Naph<^>C* derivatives becomes orange (1A, 2A) or white (3A, dual blue and yellow emission) due to the operating - intermolecular interactions. We have investigated the potential use of these materials for solid-state lighting (SSL) applications. OLEDs with different architectures containing mixtures of 1B and 3A in different ratios as dopants were fabricated. In addition, two-component white light remote phosphors were obtained by stacking different combinations of 1B or 3B as the blue emitter with [Pt(bzq)(CN)(CNXyl)] (R) (bzq = benzoquinolate, Xyl = 2,6-dimethylphenyl) as the red emitter using a 365 nm LED as pumping source. By changing the blue:red ratio, warm white light with optimal CRI and D-uv values and a great range of nominal CCT (4000-2000 K) was obtained.