Carbonized polymer dots assisted thermally activated delayed fluorescence to achieve stronger luminescence

Abstract

Carbonized polymer dots (CPDs) feature a strongly cross-linked system with a large number of energy levels, which limits the vibration and rotation of the luminous center, reduces non-radiative relaxation deactivation, and allows for cross-linking-enhanced emission (CEE). This study first predicted the rationality of designing thermally activated delayed fluorescence (TADF) molecules using theoretical calculations of electronic structure and interaction region indicators (IRI), and then introduced a highly cross-linked system of carbonized polymer dots to stabilize the triplet state of TADF and confine the vibrational and rotational relaxation. Finally, it is demonstrated through experiments, molecular electrostatic potential (MESP) analysis, and electron density difference maps that the luminescence mechanism between CPDs and TADF is due to the formation of O–H⋯N hydrogen bond interactions, which promote the reverse intersystem crossing process of thermally activated delayed fluorescence, which achieves high photoluminescence quantum yield (PLQY) in powder state and solves the problem of TADF stability. The PLQY of Ph-tBuCz@CPDs is 34.40 %, and the PLQY of Ph-DPCz@CPDs is 30.57 %. The produced TADF molecules and TADF@CPDs were used to detect electrochemiluminescence (ECL) signals, demonstrating the multifunctionality of TADF materials and proposing a specific notion for material design in biosensing.