tert-Butylated spirofluorene derivatives with arylamine groups for highly efficient blue organic light emitting diodes

A series of tert-butylated spirofluorene derivatives incorporating a diphenylaminoaryl-vinyl group was synthesized via the Horner–Wadsworth–Emmons olefination and a Suzuki cross-coupling reaction. To examine the electroluminescent properties of these materials, multilayered OLEDs were fabricated into the following device structure: ITO/DNTPD/NPB/MADN:blue dopant materials 1–14/Alq₃/Liq/Al. All devices showed efficient blue emission. In particular, one device exhibited highly efficient sky blue emission with a maximum luminance of 25100 cd m⁻² at 8.5 V, as well as luminous, power and external quantum efficiencies of 9.5 cd A⁻¹, 5.1 lm W⁻¹ and 6.7% at 20 mA cm⁻², respectively. The peak wavelength of electroluminescence was 458 and 484 nm with CIE_x,y coordinates of (0.14, 0.21) at 8.0 V. In addition, a deep blue device with CIE_x,y coordinates of (0.15, 0.15) at 8.0 V showed a luminous efficiency and external quantum efficiency of 3.8 cd A⁻¹ and 3.3% at 20 mA cm⁻², respectively.