Highly Efficient, Simplified Monochrome and White Organic Light‐Emitting Devices based on Novel Exciplex Host

The exciplex co-host system is one of the most promising candidates for developing phosphorescent organic light-emitting diodes (OLEDs) with high performance. However, highly effective exciplex co-host system that is able to realize color-pure monochrome OLED and superior color-stable white OLED simultaneously is rarely reported so far. Herein, a novel exciplex co-host system formed by the donor of (N,N '-dicarbazolyl-3,5-benzene) (MCP) and the acceptor of 4,6-bis[3,5-(dipyrid-3-yl)-phenyl]-2-phenylpyrimidine (B4PyPPM) is constructed successfully to achieve efficient phosphorescent OLEDs. By employing simple device structure with only two organic transport materials, the blue, green, orange, and red phosphorescent OLEDs based on the universal exciplex co-host exhibit stable color purity as well as maximum external quantum efficiencies of 20.1%, 26.3%, 24.6%, 19.8%, respectively. By combining blue and orange emitters, white OLED with a high efficiency of 73.6 lm W-1 is demonstrated with an extremely minor Commission Internationale de L, Eclairage coordinates variation of (0.008, 0.002) over a large luminance range, which is attributed to the balanced charge transport property and multiple funneling energy transfer paths.