Platinum(II) Complexes with Carbene Pincer Chelates for Blue Hyperphosphorescent Organic Light-Emitting Diodes

Pt(II) complexes featuring dicarbene pincer chelates have emerged as promising phosphors for the fabrication of blue organic light-emitting diodes (OLEDs); however, challenges persist in achieving both high-performance and concentration-independent color chromaticity. Herein, we present a series of Pt(II) complexes featuring a carbene pincer backbone and N-mesityl appendages, together with a complementary chloride and pyrazolate entity. These blue Pt(II) phosphors, Ptn, with n = 1-5, exhibit a high photoluminescence quantum yield (PLQY) and accelerated radiative transition rate constant (k_r), while the corresponding chloride-to-pyrazolate substitution afforded the "AgCl"-coordinated products Pt3Ag and Pt4Ag in the presence of Ag₂O. The representative phosphorescent OLED (PhOLED) based on Pt(II) phosphor Pt2 achieved a max. external quantum efficiency (EQE_max) of 20.1% and a luminance exceeding 100,000 cd m^-2, with no excimer emission even at high doping concentrations. Furthermore, upon the addition of the terminal emitter BCzBN, the resulting hyper-OLED device maintained high EQE values of 21.6% and 18.3% at 1000 and 10,000 cd m^-2, respectively. These results validated the pivotal role of N-aryl substitution in carbene pincer chelates for developing Pt(II) emitters aimed at efficient blue PhOLED devices.