Exceptionally stable blue phosphorescent organic light-emitting diodes

Blue phosphorescent organic light-emitting diodes (PhOLEDs) can deliver superior electroluminescence efficiencies than blue fluorescent OLEDs; however, their commercial debut has been delayed by short device lifetimes, especially for deep-blue PhOLEDs with Commission International de l’Eclairage y co-ordinates of less than 0.20. Here we report the use of new dopant and host materials to create a blue PhOLED device with a y co-ordinate of 0.197 and a long device lifetime of LT70 = 1,113 h [Initial luminance (L0) = 1,000 cd m–2]. Introducing bulky 3,5-di-tert-butyl-phenyl into the N-heterocyclic carbene moiety in the Pt(II) complex enhanced the photochemical stability of the high-lying metal-centred triplet state and prevented undesirable host–guest interactions, contributing to a longer device lifetime and higher colour purity. For the exciplex-forming host, the hole-transporting and electron-transporting host materials utilized a triphenylsilyl group for enhanced stability, which also improved the device lifetime.