Enhancing Large-Area Scintillator Detection with Photonic Crystal Cavities

Scintillators are materials that emit visible photons when bombarded by high-energy particles (X-ray, γ-ray, electrons, neutrinos, etc.) and are crucial for applications, including X-ray imaging and high-energy particle detection. Here, we show that one-dimensional (1D) photonic crystal (PhC) cavities, added externally to scintillator materials, can be used to tailor the intrinsic emission spectrum of scintillators via the Purcell effect. The emission spectral peaks can be shifted, narrowed, or split, improving the overlap between the scintillator emission spectrum and the quantum efficiency (QE) spectrum of the photodetector. As a result, the overall photodetector signal can be enhanced by over 200%. The use of external PhC cavities especially benefits thick and large-area scintillators, which are needed to stop particles with ultrahigh energy, as in large-area neutrino detectors. Our findings should pave the way to greater versatility and efficiency in the design of scintillators for applications, including X-ray imaging and positron emission tomography

Polarization-Resolved Plasmon-Modulated Emissions of Quantum Dots Coupled to Aluminum Dimers with Sub-20 nm Gaps

An aluminum dimer nanoantenna with nanogaps is an ideal platform for enhancing light–matter interaction at the nanoscale for the UV–vis spectrum, but its realization has been hindered by the surface oxidation of aluminum nanostructures, aluminum interband loss, and practical limitations in lithographic patterning. Here, we have overcome these problems and demonstrated the successful fabrication of an aluminum dimer antenna with a ∼10 nm gap, which to the best of our knowledge marks the smallest features of an Al nanoantenna. We present the first in-depth study of strongly polarization-dependent emissions of colloidal quantum dots coupled with Al dimers and elucidate the individual contributions of the excitation intensity, quantum yield, and extraction efficiency enhancements from numerical and experimental perspectives. We estimate the Purcell effect corresponding to a single Al-dimer antenna as ∼104 by taking into account the ensemble averaging effect and the distributions in emitter dipole orientations. This finding brings us a step closer toward a cost-effective realization of bright and ultrafast single emitters

Thermal Quenching and Dose Studies of X‑ray Luminescence in Single Crystals of Halide Perovskites

Temperature- and dose-dependent measurements of X-ray luminescence (XL) in various perovskite single crystals are reported. For methylammonium lead halide perovskites (MAPbX₃, MA = methylammonium, X = Cl, Br, or I), the quenching temperature of XL intensities shifts to lower temperatures in the sequence from Cl to I. This quenching is strongly affected by the decrease of the thermal activation energy Δ<i>E</i>_q from 53 ± 3 to 6 ± 1 meV. We replace MA in MAPbBr₃ with Cs and observe that the quenching temperature even shifts to lower temperature. But unlike the MAPbX₃ perovskites, the quenching in CsPbBr₃ is now affected by the increase of the ratio between the thermal quenching rate and the radiative transition rate (Γ₀/Γ_v) from 15 ± 1 to 66 ± 14. The same influence was observed if we dope MAPbBr₃ with Bi³⁺, Γ₀/Γ_v increases to 78 ± 18 for crystal with Bi/Pb ratio of 1:10 in precursor solution. For larger dose of X-ray, we observe that the XL intensities are still linear without saturation. Unlike temperature-dependent measurements, we do not observe the line width narrowing in dose-dependent XL spectra. Thus, this scintillator is still stable with the large X-ray dose in comparison with the variation in the temperature

Thermal Quenching and Dose Studies of X‑ray Luminescence in Single Crystals of Halide Perovskites

Temperature- and dose-dependent measurements of X-ray luminescence (XL) in various perovskite single crystals are reported. For methylammonium lead halide perovskites (MAPbX₃, MA = methylammonium, X = Cl, Br, or I), the quenching temperature of XL intensities shifts to lower temperatures in the sequence from Cl to I. This quenching is strongly affected by the decrease of the thermal activation energy Δ<i>E</i>_q from 53 ± 3 to 6 ± 1 meV. We replace MA in MAPbBr₃ with Cs and observe that the quenching temperature even shifts to lower temperature. But unlike the MAPbX₃ perovskites, the quenching in CsPbBr₃ is now affected by the increase of the ratio between the thermal quenching rate and the radiative transition rate (Γ₀/Γ_v) from 15 ± 1 to 66 ± 14. The same influence was observed if we dope MAPbBr₃ with Bi³⁺, Γ₀/Γ_v increases to 78 ± 18 for crystal with Bi/Pb ratio of 1:10 in precursor solution. For larger dose of X-ray, we observe that the XL intensities are still linear without saturation. Unlike temperature-dependent measurements, we do not observe the line width narrowing in dose-dependent XL spectra. Thus, this scintillator is still stable with the large X-ray dose in comparison with the variation in the temperature

A₂B_<i>n</i>–1Pb_<i>n</i>I_3<i>n</i>+1 (A = BA, PEA; B = MA; <i>n</i> = 1, 2): Engineering Quantum-Well Crystals for High Mass Density and Fast Scintillators

Quantum-well (QW) hybrid organic–inorganic perovskite (HOIP) crystals, e.g., A2PbX4 (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 resulted in new structures, namely A2BPb2X7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A2MAPb2I7 crystals exhibit a high mass density of >3.0 g/cm3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A2PbI4 and PEA2MAPb2I7 show emission under X- and γ-ray excitations. We further observe that some QW HOIP iodide scintillators exhibit shorter radiation absorption lengths (∼3 cm at 511 keV) and faster scintillation decay time components (∼0.5 ns) compared to those of QW HOIP bromide scintillators. Finally, we investigate the light yields of iodide-based QW HOIP crystals at 10 K (∼10 photons/keV), while at room temperature they still show pulse height spectra with light yields between 1 and 2 photons/keV, which is still >5 times lower than those for bromides. The lower light yields can be the drawbacks of iodide-based QW HOIP scintillators, but the promising high mass density and decay time results of our study can provide the right pathway for further improvements toward fast-timing applications

A₂B_<i>n</i>–1Pb_<i>n</i>I_3<i>n</i>+1 (A = BA, PEA; B = MA; <i>n</i> = 1, 2): Engineering Quantum-Well Crystals for High Mass Density and Fast Scintillators

Quantum-well (QW) hybrid organic–inorganic perovskite (HOIP) crystals, e.g., A2PbX4 (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 resulted in new structures, namely A2BPb2X7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A2MAPb2I7 crystals exhibit a high mass density of >3.0 g/cm3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A2PbI4 and PEA2MAPb2I7 show emission under X- and γ-ray excitations. We further observe that some QW HOIP iodide scintillators exhibit shorter radiation absorption lengths (∼3 cm at 511 keV) and faster scintillation decay time components (∼0.5 ns) compared to those of QW HOIP bromide scintillators. Finally, we investigate the light yields of iodide-based QW HOIP crystals at 10 K (∼10 photons/keV), while at room temperature they still show pulse height spectra with light yields between 1 and 2 photons/keV, which is still >5 times lower than those for bromides. The lower light yields can be the drawbacks of iodide-based QW HOIP scintillators, but the promising high mass density and decay time results of our study can provide the right pathway for further improvements toward fast-timing applications

A₂B_<i>n</i>–1Pb_<i>n</i>I_3<i>n</i>+1 (A = BA, PEA; B = MA; <i>n</i> = 1, 2): Engineering Quantum-Well Crystals for High Mass Density and Fast Scintillators

Quantum-well (QW) hybrid organic–inorganic perovskite (HOIP) crystals, e.g., A2PbX4 (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 resulted in new structures, namely A2BPb2X7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A2MAPb2I7 crystals exhibit a high mass density of >3.0 g/cm3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A2PbI4 and PEA2MAPb2I7 show emission under X- and γ-ray excitations. We further observe that some QW HOIP iodide scintillators exhibit shorter radiation absorption lengths (∼3 cm at 511 keV) and faster scintillation decay time components (∼0.5 ns) compared to those of QW HOIP bromide scintillators. Finally, we investigate the light yields of iodide-based QW HOIP crystals at 10 K (∼10 photons/keV), while at room temperature they still show pulse height spectra with light yields between 1 and 2 photons/keV, which is still >5 times lower than those for bromides. The lower light yields can be the drawbacks of iodide-based QW HOIP scintillators, but the promising high mass density and decay time results of our study can provide the right pathway for further improvements toward fast-timing applications

A₂B_<i>n</i>–1Pb_<i>n</i>I_3<i>n</i>+1 (A = BA, PEA; B = MA; <i>n</i> = 1, 2): Engineering Quantum-Well Crystals for High Mass Density and Fast Scintillators

Quantum-well (QW) hybrid organic–inorganic perovskite (HOIP) crystals, e.g., A2PbX4 (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 resulted in new structures, namely A2BPb2X7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A2MAPb2I7 crystals exhibit a high mass density of >3.0 g/cm3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A2PbI4 and PEA2MAPb2I7 show emission under X- and γ-ray excitations. We further observe that some QW HOIP iodide scintillators exhibit shorter radiation absorption lengths (∼3 cm at 511 keV) and faster scintillation decay time components (∼0.5 ns) compared to those of QW HOIP bromide scintillators. Finally, we investigate the light yields of iodide-based QW HOIP crystals at 10 K (∼10 photons/keV), while at room temperature they still show pulse height spectra with light yields between 1 and 2 photons/keV, which is still >5 times lower than those for bromides. The lower light yields can be the drawbacks of iodide-based QW HOIP scintillators, but the promising high mass density and decay time results of our study can provide the right pathway for further improvements toward fast-timing applications

A₂B_<i>n</i>–1Pb_<i>n</i>I_3<i>n</i>+1 (A = BA, PEA; B = MA; <i>n</i> = 1, 2): Engineering Quantum-Well Crystals for High Mass Density and Fast Scintillators

Quantum-well (QW) hybrid organic–inorganic perovskite (HOIP) crystals, e.g., A2PbX4 (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 resulted in new structures, namely A2BPb2X7 perovskite crystals, and they may have promising optical and scintillation properties toward higher mass density and fast timing scintillators. In this article, we investigate the crystal structure as well as optical and scintillation properties of iodide-based QW HOIP crystals, A2PbI4 and A2MAPb2I7. A2PbI4 crystals exhibit green and red emission with the fastest PL decay time <1 ns, while A2MAPb2I7 crystals exhibit a high mass density of >3.0 g/cm3 and tunable smaller bandgaps <2.1 eV resulting from quantum and dielectric confinement. We observe that A2PbI4 and PEA2MAPb2I7 show emission under X- and γ-ray excitations. We further observe that some QW HOIP iodide scintillators exhibit shorter radiation absorption lengths (∼3 cm at 511 keV) and faster scintillation decay time components (∼0.5 ns) compared to those of QW HOIP bromide scintillators. Finally, we investigate the light yields of iodide-based QW HOIP crystals at 10 K (∼10 photons/keV), while at room temperature they still show pulse height spectra with light yields between 1 and 2 photons/keV, which is still >5 times lower than those for bromides. The lower light yields can be the drawbacks of iodide-based QW HOIP scintillators, but the promising high mass density and decay time results of our study can provide the right pathway for further improvements toward fast-timing applications

Tailoring the Optical and Electronic Properties of 2D Hybrid Dion–Jacobson Copper Chloride Perovskites

The upsurge of low-dimensional Dion–Jacobson (DJ) phase perovskites has brought significant interest in view of their appealing stability against harsh environmental conditions as well as their promising performance in optoelectronic applications. Few reports to date have concentrated on the fundamental relationship of fine-tuning the control of diamine-based perovskite single crystals toward their electronic properties and optical behaviors. Here, we demonstrate that cationic control is proposed to regulate the role of hydrogen bonding of organic ligands with the edge-sharing [CuCl6]4– octahedral layers, leading to strong differences in the material excitonic profile and tunability of their electronic properties. Interestingly, we observe a significant reduction of photoluminescence intensity upon controlling the Cu2+/Cu+ proportion in this hybrid system. According to the photoemission measurements, variation in the oxidation states of Cu cations plays a crucial role in stabilizing the diammonium-based perovskite geometric structure. Interestingly, we find that the electronic signatures of the singlet spin-state and high-energy region transition are not influenced by the thermal effect, as probed by temperature-dependent X-ray absorption spectroscopy (XAS) at elevated temperature. Density functional calculations suggest that such an electronic difference originates from the hydrogen bonding reduction that altered the magnitude of the octahedral distortion within the DJ layered structure. As a result, the 3+NHC4H9NH3+ conformation produces a non-negligible interaction toward tuning the optical and electronic properties of DJ copper-based perovskites