Nondoped deep-blue fluorescent organic electroluminescent device with CIE_y = 0.06 and low efficiency roll-off based on carbazole/oxadiazole derivatives

摘要

Deep-blue organic light-emitting diodes (OLEDs) with the Commission Internationale de L'e'clairage (CIE) coordinates matching the European Broadcasting Union (EBU) standard blue CIE (x, y) coordinates of (0.15, 0.06) are very limited and in enormous demands. Here, we designed and synthesized four blue-emitting compounds with D-A structures based on carbazole and oxadiazole units. After the systematic studies of their photophysical, thermal and electrochemical properties, it is found that their photoluminescent properties were tuned successfully via changing the electronic structures of Ar group connecting with the oxadiazole and they all have high photoluminescent quantum yields (PLQYs). Then we selected the outstanding one as the emitter to prepare nondoped deep-blue OLEDs. The devices have maximum brightness up to 4406 cd m(-2) and high maximum external quantum efficiency (EQE) up to 4.0% along with very small efficiency roll-off. Furthermore, the CIE coordinates of (0.16, 0.06) almost reaches the EBU standard blue. The comprehensive performance of the device is competitive among the best reported nondoped deep-blue fluorescent OLEDs with EBU standard blue CIE coordinates.