Description General description mDCBPy is a thermally activated delayed fluorescent (TADF) emitter, bearing a benzoylpyridine core as an electron accepting unit and two meta carbazolyl groups as electron donating units. This TADF emitter exhibits high-contrast reversible tunable emission and can be utilized in rewritable media. Blue and green OLEDs using mDCBP as the emitter achieved a maximum EQE value of 18.4 to 14.7%, and brightness reached up to 8900 cd m-2.