Quantum-well (QW) hybrid organic-inorganic perovskite (HOIP) crystals, e.g. A2Pb2X4 (A = BA, PEA, X = Br, I), demonstrated significant potentials as scintillating materials for wide energy radiation detection compared to their individual three-dimensional (3D) counterparts, e. g. BPbX3 (B = MA). Inserting 3D into QW structures resulting new structures namely A2BPb2X7 perovskite crystals and they may have promising optical and scintillation properties towards higher mass density and fast timing scintillators. In this article, we investigate the crystal structure, optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with fastest PL decay time < 1 ns, while A2MAPb2I7 crystals exhibit high mass density of > 3.0 g/cm3, and tunable smaller band gaps < 2.1 eV resulting from quantum and dielectric confinement. We observe that only PEA cation-based A2MAPb2I7 shows emission under X- and γ-ray excitations. We further observe that QW HOIP iodide scintillators exhibit shorter radiation absorption length (~3 cm at 511 keV) and faster decay time component (~0.5 ns) compared to QW HOIP bromide scintillators. We investigate the light yields of both QW HOIP crystals (> 7 photons/keV) at 10 K, while at room temperature are still low > 0.6 photons/keV compared to our previously reported QW bromide crystals (10-40 photons/keV). Thus, promising results of our study on iodide-based QW HOIP scintillators provide the right pathway for further enhancement towards fast-timing applications.
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Fig. S1. Rietveld refinement of crystal XRD diffractograms of (a) (PEA)2PbI4, (b) (PEA)2MAPb2I7, (c) (BA)2PbI4, and (d) (BA)2MAPb2I7 crystals. Fig. S2. Absorption spectra and their fitting curves with Elliot method. Fig. S3. (a) Absorption and PL spectra excited at 375 nm with a logarithmic scale of y-axis recorded at RT. Fig. S4. TRPL decay curve excited at 532 nm monitoring 620 nm emission at RT of (a) (PEA)2PbI4, (b) (PEA)2MAPb2I7, (c) (BA)2PbI4 crystals. Fig. S5. RL spectra mapping at different temperatures from 10 to 350 K for (a) (PEA)2PbBr4, (b) (BA)2PbBr4, (c) (PEA)2PbI4, (d) (PEA)2MAPb2I7, (e) (BA)2PbI4, and (f) (BA)2MAPb2I7 crystals. Fig. S6. Delay distributions at 10 mV with 22Na source emitting two 511 keV γ-rays back-to-back and CTR sample versus leading edge threshold values. Fig. S7. The normalized light yields calculated from pulse height spectra of (PEA)2MAPb2I7 with exposing radiation time.