Polymer Electrochemiluminescence Featuring Thermally Activated Delayed Fluorescence.

Electrochemiluminescence (ECL) based on conjugated polymers or oligomers is persistently being pursued owing to its huge application scope ranging from ultra-sensitive bioanalysis to ultra-resolution imaging and spectra. Unfortunately, because of theoretical limit in radiative exciton generation yield (typically ~ 25%) of those polymers or oligomers, until now, the corresponding ECL efficiency is still limited. Herein, for the first time, we reported the ECL based on thermally activated delayed fluorescence (TADF) polymer scaffold, which is characteristic of all-exciton harvesting superiority in ECL process, and thus is potentially capable of achieving ~100% ECL efficiency. Such superiority of TADF polymer ECL was attributed to fast and efficient up-conversion process from non-radiative triplets to radiative singlets under thermal activation, which was absent in conventional fluorescent polymers/oligomers, such as F8BT. In this study, various ECL mode including annihilation or co-reactant mode using TPrA or S 2 O 8 2- as co-reactant were confirmed for our model TADF polymer ECL system, which was different from fluorescent polymer ECL counterpart. At last, solid-state ECL sensing on L-cysteine (an important marker of disease) was also evaluated by using the model TADF polymer. Simultaneously, ultralow detection limit, high sensitivity and good specificity were achieved for it. Bright future is thus anticipated for the TADF polymer scaffold in the whole ECL field.