Fused Cycloalkyl Unit-Functionalized Tetradentate Pt(II) Complexes for Efficient and Narrow-Emitting Deep Blue Organic Light-Emitting Diodes.

A blue tetradentate Pt(II) complex named Pt-tmCyCz is developed by introducing a cycloalkyl unit fused to carbazole to improve the rigidity and bulkiness of the complex. The introduction of the tetramethylcyclohexyl (tmCy) group results in a narrow full width at half maximum (FWHM), a high horizontal emitting dipole orientation, doping concentration resistant stable spectrum, and extremely small efficiency roll-off, and little concentration quenching effect. Phosphorescent organic light-emitting diodes (OLEDs) doped with Pt-tmCyCz achieve a high external quantum efficiency (EQE) of 21.5%, with a small EQE roll-off of 3.8% up to 1000 cd m -2 , a small FWHM of 24 nm, and a color coordinate of (0.132, 0.138). Moreover, Pt-tmCyCz is investigated as a sensitizer in phosphor-sensitized OLEDs using N 7 ,N 7 ,N 13 ,N 13 ,5,9,11,15-octaphenyl-5,9,11,15-tetrahydro-5,9,11,15-tetraaza-19b,20b-diboradinaphtho[3,2,1-de:1',2',3'-jk]pentacene-7,13-diamine (νDABNA) as a terminal emitter. The Pt-tmCyCz:νDABNA device achieves a high EQE of 33.9%, with a small EQE roll-off of only 8.0% up to 1 000 cd m -2 . The results demonstrate that fused tmCy group in carbazole can be an effective building block for the development of high-performance Pt(II) complexes, which can be utilized as efficient phosphors or sensitizers in OLEDs.