Fused Cycloalkyl Unit‐Functionalized Tetradentate Pt(II) Complexes for Efficient and Narrow‐Emitting Deep Blue Organic Light‐Emitting Diodes
Kiun Cheong, Unhyeok Jo, Wan Pyo Hong, Jun Yeob Lee
Abstract
Abstract 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.