We have introduced into the TADF toolbox azaborine as a very weak donor moiety for the construction of D-A TADF emitters. As an electron donor AZB is weak like carbazole, but due to its size and shape adopts a perpendicular conformation in D-A systems similar to DMACcontaining compounds. Together, these properties lead to blue-shifted PL while retaining TADF activity. In the presented example materials, AZB-TRZ exhibits overall better TADF properties and OLED performance than those of AZB-Ph-TRZ because of its smaller DEST and good FPL.