Polyphenylbenzene as a platform for deep-blue OLEDs: Aggregation enhanced emission and high external quantum efficiency of 3.98%

Great efforts have been devoted to seek novel approaches for the construction of efficient deep-blue fluorescent materials, one of the most important prerequisites for the commercialization of OLEDs. Here, we report a new way to utilize polyphenylbenzene as a platform to yield a series of efficient deep-blue emitters. Nondoped multilayer electroluminescence (EL) devices using these new luminogens as emitting layers are fabricated. Maximum current efficiency (CE) of 2.0 cd A^-1 is achieved and the Commission Internationale de léclairage (CIE) coordinates can stay at (0.15, 0.08), close to the saturated deep-blue (0.14, 0.08). Through rational design of the device structure, blue-violet emission with the CIE coordinates of (0.15, 0.06) can be realized. Furthermore, 10-based doped devices show deep-blue emission with improved CE as high as 4.51 cd A^-1, and the external quantum efficiency (EQE) of 3.98%, which are among the best EL performance for deep-blue emission.