Highly efficient blue thermally activated delayed fluorescence (TADF) materials consisting of 9,9-diphenylacridan and benzonitrile units were developed. We found that placing 9,9-diphenylacridan in the ortho-position of benzonitrile enhanced the TADF process compared with results from meta-and para-substituted derivatives. We observed blue TADF emission with a high photoluminescence quantum yield (80%) and a high reverse intersystem crossing rate constant (1.2 x 10(6) s(-1)) for 2,6-bis(9,9-diphenylacridan-10(9H)-yl)benzonitrile (o-A2CN). An organic light-emitting diode fabricated using o-A2CN as an emitter showed good blue emission (CIEx, CIEy = 0.16, 0.16) with high external electroluminescence quantum efficiency (15.9%).