Concentration Quenching Behavior of Thermally Activated Delayed Fluorescence in a Solid Film

Concentration-dependent photophysical properties were investigated using an approach for more rigorous interpretation through well-defined concentration quenching equations derived from an optical exciton model. These calculations verified that the solid-state self-quenching process of the 1,2,3,5-tetrakis(carbazol-9-yl)-4,6-dicyanobenzne (4CzIPN) emitter in a host matrix is controlled by the Dexter energy transfer model. By extension, we found that the reduction in the radiative singlet decay rate (krS) can be ascribed to the stabilization of excited states. This process may increase the efficiency of intersystem crossing as the doping concentration of 4CzIPN increases in the host material in a solid matrix. Furthermore, the nonradiative triplet decay process (knrT) could be an important consideration for estimating the exact concentration quenching rate constant value and the efficiency of reverse intersystem crossing corresponding to experimental photoluminescence behaviors with the various doping concentrations.