Carbazole end-capped pyrene starburst with enhanced electrochemical stability and device performance

Carbazole end-capped starburst molecule based on pyrene core "4CzFP" was synthesized and characterized. The starburst material shows good film-forming ability and bright blue fluorescence. In cyclic voltammetry test, 4CzFP shows a high highest occupied molecular orbital energy level of -5.26 eV, indicating it has good hole-injection ability. The material is quite stable under series of cyclic voltammetry scans, implying its good electrochemical stability. Single-layered electroluminescent device takes on stable blue emission with a peak current efficiency of 0.84 cd/A. Double-layered device by adding Poly(N-vinylcarbazole) (PVK) as a hole-injection layer does not show any improvement, indicating that 4CzFP could be efficiently used as the hole-injection/light-emitting layer. The device performance is largely improved by adding a thin TPBI electron-injection/transporting layer. The peak efficiency reaches 3.28 cd/A and the maximum brightness is over 2200 cd/m ².