A Plastic Scintillator Based on an Efficient Thermally Activated Delayed Fluorescence Emitter 9‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)‐2‐methylphenyl)‐3,6‐dioctyl‐9H‐carbazole for Pulse Shape Discrimination Measurement

Abstract

Pulse shape discrimination (PSD)‐capable plastic scintillator is in demand for the detection of high‐energy neutrons in the presence of gamma radiation background. Conventional PSD plastics are based on delayed fluorescent dye via triplet–triplet annihilation of a fluorescent dye additive, which is inefficient to harvest the energy of triplet excitons. In recent years, thermally activated delayed fluorescence (TADF) emitters have gained substantial success in organic light‐emitting diodes due to their efficient utilization of the energy of triplet excitons and thereby achieving theoretical unity internal quantum efficiencies. Herein, a highly efficient TADF dye 9‐(4‐(4,6‐diphenyl‐1,3,5‐triazin‐2‐yl)‐2‐methylphenyl)‐3,6‐dioctyl‐9H‐carbazole is reported for the PSD application. This TADF dye may be loaded up to 30 wt% in polyvinyltoluene matrix and still retains high optical transparency. High scintillation light yield and PSD figures of merit are obtained from the TADF plastic. With the introduction of a secondary dye to further increase the utilization efficiency of the excitation energy, the light yield is increased to 6948 photons MeV−1. The measured alpha/gamma PSD figure of merit is 1.12 at the energy threshold of 100 keVee and neutron/gamma PSD figure of merit is 1.32 at the threshold of 1000 keVee.

An approach towards plastic scintillators from thermally activated delayed fluorescent dyes and cross-linkable bismuth compounds

“…In these so-called TADF dyes, a small energy gap between singlet and triplet excited states enables efficient reverse intersystem crossing (RISC) at room temperature and LQY values that can approach 100% and are consequently attractive to increase the light yield of plastic scintillators. 8–11…”

“…To date reports on the use of TADF dyes in plastic scintillators with a polyvinyltoluene (PVT) polymer matrix remain scarce. 9,10 In these studies, PVT scintillators loaded with TADF dyes such as 9-(4-3-[4-(3,6-dioctyl-9 H -carbazol-9-yl)benzene-sulfonyl]benzene-sulfonyl phenyl)-3,6-dioctyl-9 H -carbazole (DOC-mBPSB at 10 wt%) and 9-(4-4-[4-(3,6-dioctyl-9 H -carbazol-9-yl)benzenesulfonyl]benzenesulfonyl phenyl)-3,6-dioctyl-9 H -carbazo le (DOC-pBPSB at 10 wt%) 10 or 9-(4-(4,6-diphenyl-1,3,5-triazin-2-yl)-2-methylphenyl)-3,6-dioctyl-9 H -carbazole (OCz-TRZ at 30 wt%) 9 where found to have limited solubility which prevented the use of higher loading ratios suitable for pulse shape discrimination (PSD) (for PSD, higher loading of fluorophores is required). In addition, none of these scintillators was loaded with compounds containing heavy elements with high atomic numbers ( Z ) such as bismuth (Bi), preventing the observation of a photopeak during detection of gamma radiation through the photoelectric effect.…”

Plastic Scintillators and Radiation Detectors Based on Triphenyl Pyrazoline Derivatives

“…During sixty years of their development organic scintillators have been optimized to have excellent luminescent characteristics [7,8,9] . Nevertheless, the research in the field recently has received a new turn due to recent “rediscovery” of a pulse shape discrimination (PSD) effect [10] .…”

“…During sixty years of their development organic scintillators have been optimized to have excellent luminescent characteristics. [7,8,9] Nevertheless, the research in the field recently has received a new turn due to recent "rediscovery" of a pulse shape discrimination (PSD) effect. [10] PSD effect allows distinguishing between different types of radiation (neutron/gamma or α/β particles) based on different relaxation kinetics of excited states created in a material due to radiation energy deposition.…”

Influence of Isomerism on Radioluminescence of Purely Organic Phosphorescence Scintillators

“…tors, the organic counterparts exhibit controllable tunability of optical properties by molecular modification, low processing temperature as well as low production cost. Therefore, series of emissive plastics, [4] liquid luminogens, [5] and organic crystals [1b, 6] were developed as scintillators for practical applications. Among them, most luminogens for scintillators are fluorescent molecules.…”