Multifunctional derivatives of pyrimidine-5-carbonitrile and differently substituted carbazoles for doping-free sky-blue OLEDs and luminescent sensors of oxygen

•Pyrimidine-5-carbonitrile-based compounds with efficient TADF exceeding reverse intersystem crossing rates of 106 s−1.•AIEE properties for the designed compounds allowing to reach PLQYs up to 50% in solid state.•Bipolar charge-transporting properties showing hole mobility of 1.6 × 10-4 cm2/V·s and electron mobility of 1.37 × 10-5 cm2/V·s.•Non-doped sky-blue OLED with external quantum efficiency of 12.8%.•Oxygen probes with fast response, high sensitivity and good stability.