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

Scintillatorsfabricated from organic-inorganic layeredperovskites have attracted wide attention due to their excellent properties,including fast decay times, superior light yield, and high excitonbinding energy. In relation to their optoelectronic properties, hybridorganic-inorganic perovskites are known for their tunability,which could be manipulated by modifying the organic cations. In thisstudy, we investigate the optical and scintillation properties oflead halide perovskites A(2)PbBr(4), where A varyfrom amylammonium (AA), hexylammonium (HA), octylammonium (OA), andbenzylammonium (BZA) organic ligands. Photoluminescence (PL) spectradisplay 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 iswithin similar to 3 eV range, which fulfill the criteria of promisingscintillators. Radioluminescence (RL) spectra show negative thermalquenching behavior (NTQ) in all samples, with the AA(2)PbBr(4) peak intensity appearing at relatively lower temperaturecompared to other samples. Thermoluminescence (TL) measurement revealstrap-free states in AA(2)PbBr(4), while other samplespossess shallow traps (<40 meV) as well as low trap density, whichis beneficial for fast-decay scintillators, X-ray detection and energyconversion for solar cells. Overall, our results demonstrate thatthe extension of linear organic chains in lead-based perovskite isa deterministic strategy for a fast response hybrid-based scintillatorto date.