Two non-doped blue emitters for electroluminescent devices: Preparation, photophysics and electroluminescence

Abstract

Two blue emitters, 2,7-bis(9-benzyl-9H-carbazol-2-yl)pyrene and 2,7-bis(4-(5-phenyl-1,3,4-oxadiazol-2-yl)phenyl)pyrene, were synthesized by a Suzuki coupling reaction. Photophysical studies show that the two emitters have excellent optical and electron transfer properties. The emission peaks of the two emitters are 430 nm and 439 nm with 87.5% and 68.6% fluorescence quantum yields in chloroform, respectively. The emitters both have good thermal stability (Td > 330 °C, Tg > 160 °C). Electrochemical Redox properties of the emitters were measured by cyclic voltammetry, and the highest occupied molecular orbital and the lowest unoccupied molecular orbital levels are in good agreement with the results of theoretical calculations. Additionally, non-doped blue organic light-emitting diodes with these emitters have been achieved with the Commission International de l’Éclairage (x,y) coordinates of (0.17, 0.11) and (0.16, 0.15) respectively, which are very close to the National Television System Committee standard blue. Remarkably, the performance of device A (2,7-bis(9-benzyl-9H-carbazol-2-yl) pyrene) offers balanced performance and without any significant disadvantages.