The electrochemistry and electrogenerated chemiluminescence (ECL) of four kinds of electron donor-acceptor molecules exhibiting thermally activated delayed fluorescence (TADF) is presented. TADF molecules can harvest light energy from the lowest triplet state by spin up-conversion to the lowest singlet state because of small energy gap between these states. Intense green to red ECL is emitted from the TADF molecules by applying a square-wave voltage. Remarkably, it is shown that the efficiency of ECL from one of the TADF molecule could reach about 50 %, which is comparable to its photoluminescence quantum yield. Donor-acceptor molecules with thermally activated delayed fluorescence (TADF) at room temperature can emit efficient electrogenerated chemiluminescence (ECL). Efficient spin up-conversion from triplet to singlet excited states through thermal activation is required to break through the theoretical limitation according to spin statistics (25 % of the quantum yield of photoluminescence). The ECL efficiency one TADF molecule reached about 50 %.
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