Organic Chain Length Effect on Trap States of Lead Halide Perovskite Scintillators

Scintillators
fabricated from organic–inorganic layered
perovskites have attracted wide attention due to their excellent properties,
including fast decay times, superior light yield, and high exciton
binding energy. In relation to their optoelectronic properties, hybrid
organic–inorganic perovskites are known for their tunability,
which could be manipulated by modifying the organic cations. In this
study, we investigate the optical and scintillation properties of
lead halide perovskites A2PbBr4, where A vary
from amylammonium (AA), hexylammonium (HA), octylammonium (OA), and
benzylammonium (BZA) organic ligands. Photoluminescence (PL) spectra
display dual peaks due to surface and bulk trap states contributions,
while fast average decay times from time-resolved photoluminescence
(TRPL) for all samples are within the range of 0.69 ± 0.11–0.99
± 0.13 ns. The optical band gap of these hybrid perovskites is
within ∼3 eV range, which fulfill the criteria of promising
scintillators. Radioluminescence (RL) spectra show negative thermal
quenching behavior (NTQ) in all samples, with the AA2PbBr4 peak intensity appearing at relatively lower temperature
compared to other samples. Thermoluminescence (TL) measurement reveals
trap-free states in AA2PbBr4, while other samples
possess shallow traps (<40 meV) as well as low trap density, which
is beneficial for fast-decay scintillators, X-ray detection and energy
conversion for solar cells. Overall, our results demonstrate that
the extension of linear organic chains in lead-based perovskite is
a deterministic strategy for a fast response hybrid-based scintillator
to date.