Plastic scintillators based on thermally activated delayed fluorescence dyes

Thermally activated delayed fluorescence (TADF) dyes are a class of luminescent organic compounds capable of the conversion of triplet to singlet excited states for increased photon emission efficiency, and these classes of dyes have recently attracted a great deal of attention for their potential use in highly efficient organic light emitting diodes (OLEDs). For organic scintillators utilizing conventional fluorescent dyes, triplet excited states generated from energy deposition of the incident particle's energy can be converted to singlets via triplet-triplet annihilation, which leads to the delayed pulse tail characteristic of organic scintillators, but is not overall a particularly efficient process for triplet to singlet conversion. In this work, we investigated the applicability of the use of TADF dyes in organic scintillators, in particular for their capability for triplet to singlet conversion, and how these unique properties impact the overall scintillation photophysics. In particular, the prospects of using TADF dyes as a means for increased light yield as well as for efficient pulse shape discrimination (PSD) properties are directly addressed. In doing do, we explored the prominent effect that the dye's singlet-triplet splitting energy (Delta E-ST) - a parameter fundamental to the realization of efficient TADF processes - has on determining these properties, and our findings suggest that TADF dyes could eventually enable an entirely new generation of high performance organic scintillators.