A new efficient blue fluorophor 4-(4-diphenylaminophenyl)diphenylsulfone (SOTPA), with high triplet energy and balanced charge-transporting properties, has been designed and synthesized, and showed impressive performance both as blue emitter and as a host for phosphors. A green phosphorescent device containing SOTPA as host showed a maximum external quantum efficiency (EQE) as high as 19.2%, suggesting almost complete triplet harvesting from the blue fluorophor by the green phosphor. Single-emitting layer (EML) F–P hybrid white organic light-emitting devices (WOLEDs) based on SOTPA also gave outstanding electroluminescence performance, with a low turn-on voltage of 2.7 V and maximum EQE and power efficiency (PE) of 15.4% and 40.2 lm W^？1, respectively. Even at a practical brightness of 1000 cd m^？2 the PE still remained as high as 24.1 lm W^？1. This excellent performance represents the highest efficiency yet reported among single-EML F–P hybrid WOLEDs. 

J. Mater. Chem. C, 2015 

Synthesis and chemical structure of SOTPA.