Oxygen-doped and fluorine-doped cesium and rubidium lead perovskite compounds for hard radiation detection

Abstract

Providing oxygen-doped and fluorine-doped cesium and rubidium lead perovskite compounds for hard radiation detection. [Solution] Provided are an inorganic perovskite doped with oxygen or fluorine atoms, a method for producing a doped perovskite, and a hard radiation detector incorporating the doped perovskite as a photoactive layer. For this doped perovskite, lead oxide, lead fluoride, or a compound that thermally decomposes into lead oxide or lead fluoride is used as the dopant atom source. During the crystallization of the perovskite in the presence of this dopant atom source, oxygen or fluoride atoms from the dopant source are incorporated into the perovskite crystal lattice.

Description

Technical Field

[0001] Cross - reference to Related Applications This application claims priority to U.S. Provisional Patent Application No. 63 / 020,176, filed May 5, 2020, the entire content of which is incorporated herein by reference.

Background Art

[0002] Preventing radioactive materials from being used for malicious purposes is a major global safety challenge. To address this difficult problem, there is a great need for highly sensitive, chemically stable, and low-cost room-temperature radiation detection semiconductors (RTSDs). An ideal RTSD requires the ability to efficiently identify low-dose radiation sources, even when the radiation is weak or shielded. To identify radiation sources with high energy resolution, candidate RTSD materials must simultaneously meet several diverse and stringent criteria. Some of the most desirable criteria are: (i) a band gap wide enough to inhibit the thermal ionization of carriers at room temperature (Eg > 1.5 eV); (ii) a high mean atomic number (Z) and density to ensure high absorption efficiency of high-energy radiation; (iii) high lattice resistance to trapping of photo-induced carriers at deep levels; (iv) absence of polarization effects in long-term performance; (v) high radiation hardness and high chemical stability; and (vi) a high carrier mobility-lifetime product (μτ) to enable the identification and characterization of various low-dose radiation sources. Due to the stringent requirements mentioned above, only a limited number of semiconductor compounds are considered promising as ionizing radiation detector materials. To date, high-purity germanium (HPGe), CdTe-based compounds, TlBr, BiI3, HgI2, and PbI2 have been identified as excellent semiconductor detector materials with spectroscopic properties. HPGe offers the best energy resolution of less than 0.8% for gamma rays, but its inherently narrow bandgap requires cooling with liquid nitrogen to operate the detector, hindering its wide range of applications. Even CdTe-based compounds, the most commercially available RTSDs, still suffer from inherent drawbacks related to Te deposition, macroscopic defects, and compositional heterogeneity. TlBr is an RTSD under development that exhibits spectroscopic properties for gamma rays, possessing high electron mobility and lifetime product (μτ) and electron lifetime. However, TlBr suffers from inherent polarization-induced instability and low mechanical hardness that is fatal to material processing. Other high-density binary semiconductor detection materials, such as HgI2, PbI2, and BiI3, have high resistance but suffer from hygroscopicity and mechanical deformability due to the properties of their two-dimensional crystal structure.

[0003] Recently, CsPbBr3, an all-inorganic semiconductor with a perovskite structure, strong photon stopping power, and high chemical stability, has been identified as a promising semiconductor radiation detector material with a high energy resolution of about 3.8% and a long hole mobility-lifetime product of 10 -3 cm 2 / V for γ-rays of 122 keV (He, Y. H. et al., Nat Commun 2018, 9, 1609). This compound is composed of Cs and Pb atoms with both high atomic numbers and has a high density due to its dense crystal structure. The high average atomic number and density ensure high photon stopping power during radiation irradiation. However, there are variations in the yield and detection performance for each batch during hard radiation irradiation, making it impossible to control the detection performance and yield.

Summary of the Invention

[0004] Oxygen-doped perovskites and fluorine-doped perovskites for use in detecting hard radiation, radiation detectors incorporating these doped perovskites, methods of using such radiation detectors, and methods of manufacturing these doped perovskites are provided.

[0005] Examples of the doped perovskites include perovskite single crystals having the chemical formula CsAX3, the chemical formula RbAX3, or the chemical formula Cs 1-x Rb x PbX3 (0 < x < 1), where in these formulas, A represents Pb or a combination of Pb and one or more of Sn, Si, and Ge, and X represents one or more halogen atoms, and the crystal lattice of this perovskite single crystal has oxygen atom dopants or fluorine atom dopants.

[0006] Examples of the device for detecting incident radiation include the chemical formula CsAX3, the chemical formula RbAX3, or the chemical formula Cs 1-xAn optoactive layer containing a perovskite single crystal having RbxPbX3 (0 < x < 1), wherein in these formulas, A represents Pb or a combination of Pb with one or more of Sn, Si, and Ge, X represents one or more halogen atoms, and the crystal lattice of this perovskite single crystal has an oxygen atom dopant or a fluorine atom dopant. The device further includes a first electrode in electrical communication with the optoactive layer; a second electrode in electrical communication with the optoactive layer; and a signal detector configured to measure the photocurrent generated in the optoactive layer when the optoactive layer is exposed to incident X-rays, γ-rays, and / or α-particles, and these first and second electrodes are configured to apply an electric field across the entire optoactive layer.

[0007] An example of a method for detecting incident radiation using the device described herein includes exposing the optoactive layer of the device to incident radiation including X-rays, γ-rays, and / or α-particles, whereby an oxygen-doped perovskite or a fluorine-doped perovskite absorbs the incident radiation and generates a photocurrent in the material; and detecting the photocurrent to measure at least one of the energy and intensity of the absorbed incident radiation.

[0008] An example of a method for producing an oxygen-doped or fluorine-doped perovskite having the chemical formula CsAX3 (wherein A represents Pb or a combination of Pb with one or more of Sn, Si, and Ge, and X represents one or more halogen atoms) includes generating a mixture of perovskites having a dopant source compound including the chemical formula CsAX3, the chemical formula RbAX3, or the chemical formula Cs 1-x Rb x PbX3 (wherein 0 < x < 1, A represents Pb, Sn, Si, Ge, or a combination of two or more thereof, and X represents one or more halogen atoms), and PbO, a lead and oxygen-containing compound that decomposes to PbO upon heating, PbF2, or a lead and oxygen-containing compound that decomposes to PbF2 upon heating; melting the perovskite and the dopant source to form a melt; and crystallizing an oxygen-doped perovskite or a fluorine-doped perovskite from the melt.

Brief Description of the Drawings

[0009] Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings, in which the same numbers indicate the same elements.

[0010] [Figure 1A] Figure 1A shows the temperature characteristics in a vertical Bridgman furnace for three temperature ranges for crystal growth. Figure 1B shows the powder X-ray diffraction (PXRD) patterns of pulverized samples from all Boule (cylindrical artificial stone) produced using various concentrations of PbO. The simulated pattern of CsPbBr3 originates from the orthorhombic room-temperature phase belonging to the Pnma space group. Figure 1C shows the current-voltage (IV) curve of a 4.0 × 4.0 × 1.0 mm³ CsPbBr3 crystal with Ga junctions (Schottky junctions) and Au junctions (ohmic contacts).

[0011] [Figure 1B-C] Figure 1A shows the temperature characteristics in a vertical Bridgman furnace for three temperature ranges for crystal growth. Figure 1B shows the powder X-ray diffraction (PXRD) patterns of pulverized samples from all Boule (cylindrical artificial stone) produced using various concentrations of PbO. The simulated pattern of CsPbBr3 originates from the orthorhombic room-temperature phase belonging to the Pnma space group. Figure 1C shows the current-voltage (IV) curve of a 4.0 × 4.0 × 1.0 mm³ CsPbBr3 crystal with Ga junctions (Schottky junctions) and Au junctions (ohmic contacts).

[0012] [Figure 2A-D]Figure 2A shows the 122 keV gamma-ray pulse height spectrum (hole collection) of a planar apparatus fabricated from oxygen-doped CsPbBr3 crystals. Figure 2B shows the 122 keV gamma-ray pulse height spectrum (hole collection) of planar apparatus fabricated from CsPbBr3 crystals using various concentrations of PbO. Figure 2C shows the hole collection efficiency as a function of the bias voltage applied to CsPbBr3 crystals fabricated using various PbO concentrations. Figure 2D shows the energy resolution for 122 keV gamma rays and the product of hole mobility and lifetime for CsPbBr3 fabricated using various PbO concentrations.

[0013] [Figure 3A] Figure 3A shows the 122 keV gamma-ray pulse height spectrum (hole collection) of a planar apparatus fabricated from CsPbBr3 crystals produced using various PbO concentrations. Figure 3B shows the electron collection efficiency as a function of the applied bias voltage for CsPbBr3 crystals produced using various PbO concentrations. Figure 3C shows the product of electron mobility and lifetime for CsPbBr3 produced using various PbO concentrations.

[0014] [Figure 3B-C] Figure 3A shows the 122 keV gamma-ray pulse height spectrum (hole collection) of a planar apparatus fabricated from CsPbBr3 crystals produced using various PbO concentrations. Figure 3B shows the electron collection efficiency as a function of the applied bias voltage for CsPbBr3 crystals produced using various PbO concentrations. Figure 3C shows the product of electron mobility and lifetime for CsPbBr3 produced using various PbO concentrations.

[0015] [Figure 4A] Figures 4A-4C show the 122 keV gamma-ray pulse height spectra (hole collection) of a planar apparatus prepared from CsPbBr3 crystals extracted from the front (Figure 4A), middle (Figure 4B), and rear (Figure 4C) ends of a Boule prepared using PbO as a dopant source compound at a concentration of 0.10%. The length of the Boule is approximately 4.0 cm.

[0016] [Figure 4B] Figures 4A-4C show the 122 keV gamma-ray pulse height spectra (hole collection) of a planar apparatus prepared from CsPbBr3 crystals extracted from the front (Figure 4A), middle (Figure 4B), and rear (Figure 4C) ends of a Boule prepared using PbO as a dopant source compound at a concentration of 0.10%. The length of the Boule is approximately 4.0 cm.

[0017] [Figure 4C] Figures 4A-4C show the 122 keV gamma-ray pulse height spectra (hole collection) of a planar apparatus prepared from CsPbBr3 crystals extracted from the front (Figure 4A), middle (Figure 4B), and rear (Figure 4C) ends of a Boule prepared using PbO as a dopant source compound at a concentration of 0.10%. The length of the Boule is approximately 4.0 cm.

[0018] [Figure 5A] Figures 5A–5D show the X-ray photoelectron spectra of Br 3d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5A); X-ray photoelectron spectra of Pb 3d electrons and O 1s electrons from undoped CsPbBr3, CsPbBr3 prepared using 0.05% PbO as a dopant source compound, and PbO (Figures 5B and 5C, respectively); and the X-ray photoelectron spectrum of Cs 4d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5D). The spectra were fitted using a standard Gaussian distribution.

[0019] [Figure 5B]Figures 5A–5D show the X-ray photoelectron spectra of Br 3d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5A); X-ray photoelectron spectra of Pb 3d electrons and O 1s electrons from undoped CsPbBr3, CsPbBr3 prepared using 0.05% PbO as a dopant source compound, and PbO (Figures 5B and 5C, respectively); and the X-ray photoelectron spectrum of Cs 4d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5D). The spectra were fitted using a standard Gaussian distribution.

[0020] [Figure 5C] Figures 5A–5D show the X-ray photoelectron spectra of Br 3d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5A); X-ray photoelectron spectra of Pb 3d electrons and O 1s electrons from undoped CsPbBr3, CsPbBr3 prepared using 0.05% PbO as a dopant source compound, and PbO (Figures 5B and 5C, respectively); and the X-ray photoelectron spectrum of Cs 4d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5D). The spectra were fitted using a standard Gaussian distribution.

[0021] [Figure 5D]Figures 5A–5D show the X-ray photoelectron spectra of Br 3d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5A); X-ray photoelectron spectra of Pb 3d electrons and O 1s electrons from undoped CsPbBr3, CsPbBr3 prepared using 0.05% PbO as a dopant source compound, and PbO (Figures 5B and 5C, respectively); and the X-ray photoelectron spectrum of Cs 4d electrons from undoped CsPbBr3 and CsPbBr3 prepared using 0.05% PbO as a dopant source compound (Figure 5D). The spectra were fitted using a standard Gaussian distribution.

[0022] [Figure 6A-B] Figures 6A and 6B show the X-ray photoelectron spectra of O 1s electrons from the surface layer of Pb metal oxidized in air (Figure 6A) and the X-ray photoelectron spectra of O 1s electrons from the surface of photodegraded dark PbBr2 powder (Figure 6B). Surface etching was not performed before the XPS measurement in order to obtain signals from the surface layer. The spectra were fitted using a standard Gaussian distribution.

[0023] [Figure 7A-B] Figures 7A–7F show the room-temperature PL spectrum of an undoped CsPbBr3 crystal using a 0.5 mW laser (Figure 7A); the room-temperature PL spectrum of CsPbBr3 crystals prepared with various PbO concentrations using a 0.5 mW laser (Figure 7B); the typical peak position and intensity as a function of PbO concentration (Figure 7C); the room-temperature time-resolved decay spectrum of emission at 524 nm for an undoped CsPbBr3 crystal (Figure 7D); the room-temperature time-resolved decay spectrum of emission at 534 nm for CsPbBr3 crystals prepared with various PbO concentrations (Figure 7E); and the average photoluminescence (PL) decay time as a function of concentration (Figure 7F).

[0024] [Figure 7C-D]Figures 7A–7F show the room-temperature PL spectrum of an undoped CsPbBr3 crystal using a 0.5 mW laser (Figure 7A); the room-temperature PL spectrum of CsPbBr3 crystals prepared with various PbO concentrations using a 0.5 mW laser (Figure 7B); the typical peak position and intensity as a function of PbO concentration (Figure 7C); the room-temperature time-resolved decay spectrum of emission at 524 nm for an undoped CsPbBr3 crystal (Figure 7D); the room-temperature time-resolved decay spectrum of emission at 534 nm for CsPbBr3 crystals prepared with various PbO concentrations (Figure 7E); and the average photoluminescence (PL) decay time as a function of concentration (Figure 7F). [Figure 7E-F] Figures 7A–7F show the room-temperature PL spectrum of an undoped CsPbBr3 crystal using a 0.5 mW laser (Figure 7A); the room-temperature PL spectrum of CsPbBr3 crystals prepared with various PbO concentrations using a 0.5 mW laser (Figure 7B); the typical peak position and intensity as a function of PbO concentration (Figure 7C); the room-temperature time-resolved decay spectrum of emission at 524 nm for an undoped CsPbBr3 crystal (Figure 7D); the room-temperature time-resolved decay spectrum of emission at 534 nm for CsPbBr3 crystals prepared with various PbO concentrations (Figure 7E); and the average photoluminescence (PL) decay time as a function of concentration (Figure 7F).

[0025] [Figure 8A-B] Figure 8A shows the room-temperature PL spectrum dependent on laser power from a sample prepared using 0.05% PbO as the dopant source compound; and also shows the room-temperature PL spectra taken from a sample prepared using 0.05% PbO as the dopant source compound at laser powers of 5 mW (Figure 8B); 2.5 mW (Figure 8C); 1 mW (Figure 8D); 0.5 mW (Figure 8E); and 0.25 mW (Figure 8F). All spectra were fitted using two Gaussian peaks (solid and dashed black lines). [Figure 8C-D]Figure 8A shows the room-temperature PL spectrum dependent on laser power from a sample prepared using 0.05% PbO as the dopant source compound; and also shows the room-temperature PL spectra taken from a sample prepared using 0.05% PbO as the dopant source compound at laser powers of 5 mW (Figure 8B); 2.5 mW (Figure 8C); 1 mW (Figure 8D); 0.5 mW (Figure 8E); and 0.25 mW (Figure 8F). All spectra were fitted using two Gaussian peaks (solid and dashed black lines). [Figure 8E-F] Figure 8A shows the room-temperature PL spectrum dependent on laser power from a sample prepared using 0.05% PbO as the dopant source compound; and also shows the room-temperature PL spectra taken from a sample prepared using 0.05% PbO as the dopant source compound at laser powers of 5 mW (Figure 8B); 2.5 mW (Figure 8C); 1 mW (Figure 8D); 0.5 mW (Figure 8E); and 0.25 mW (Figure 8F). All spectra were fitted using two Gaussian peaks (solid and dashed black lines).

[0026] [Figure 9] Figure 9 shows a plot of the logarithmic values ​​(of PL intensity) versus the logarithmic values ​​(of laser power) against the observed peaks.

[0027] [Figure 10A] Figure 10A is a graph of the 122 keV gamma-ray pulse height spectrum (electron harvesting) of a planar apparatus fabricated from oxygen-doped CsPbBr2Cl crystals. Figure 10B is a graph of the room-temperature PL spectrum of oxygen-doped CsPbBr2Cl crystals.

[0028] [Figure 10B] Figure 10A is a graph of the 122 keV gamma-ray pulse height spectrum (electron harvesting) of a planar apparatus fabricated from oxygen-doped CsPbBr2Cl crystals. Figure 10B is a graph of the room-temperature PL spectrum of oxygen-doped CsPbBr2Cl crystals.

[0029] [Figure 11A] Figure 11A shows the PL lifetime of an oxygen-doped sample of CsPbBr2Cl (0.2% PbO). Figure 11B shows the PL lifetime of an oxygen-doped sample of CsPbBr2Cl (1% PbO). As the doping concentration decreases, the decay time increases.

[0030] [Figure 11B] Figure 11A shows the PL lifetime of an oxygen-doped sample of CsPbBr2Cl (0.2% PbO). Figure 11B shows the PL lifetime of an oxygen-doped sample of CsPbBr2Cl (1% PbO). As the doping concentration decreases, the decay time increases.

[0031] [Figure 12] Figure 12 shows the gamma-ray spectra obtained from two different oxygen-doped samples of CsPbBr2Cl, where the spectral resolution can be controlled by the amount of added PbO dopant source.

[0032] [Figure 13] Figure 13 shows the gamma-ray spectrum obtained from a CsPbBr2.83I0.17 sample doped with a PbO oxygen dopant source. A radiation detector made from oxygen-doped CsPbBr2.83I0.17, which decomposes the energy of a 57-Co source, was able to detect g-rays at 122 keV. The sample was doped with a PbO concentration of 0.5%.

[0033] [Figure 14A] Figures 14A and 14B show the PL lifetime of a fluorine-doped CsPbBr3 sample (0.5% PbF2) (Figure 14A) and an undoped CsPbBr3 material (Figure 14B). The significant increase in PL decay time is attributable to the fluorine dopant. This may be due to a reduction in the vacancy concentration of the halide (e.g., Br).

[0034] [Figure 14B]Figures 14A and 14B show the PL lifetimes of a fluorine-doped CsPbBr3 sample (0.5% PbF2) (Figure 14A) and an undoped CsPbBr3 material (Figure 14B). The significant increase in the PL decay time is due to the fluorine dopant. This may be due to a reduction in the vacancy concentration of the halide (e.g., Br).

Embodiments of the Invention

[0035] Provided are inorganic perovskites doped with oxygen atoms and / or fluorine atoms, and a method for producing the doped perovskites. Further provided are radiation detectors incorporating the doped perovskite as a photoactive layer, and a method for detecting hard radiation such as X-rays, γ-rays, and / or α-particles using the radiation detector.

[0036] The perovskite has the general formula CsAX3, the chemical formula RbAX3, or the chemical formula Cs 1-x Rb x PbX3 (0 < x < 1) and has a standard or distorted perovskite structure, where A is a combination of Pb or Pb and one or more additional elements selected from Group IVA (Group 14) of the Periodic Table of the Elements, and X represents one or more halogen atoms. Examples of atoms of A include Si, Sn, Ge, and Pb atoms. When A contains two or more elements from Group IVA, the molar ratio of the A element to Cs is 1:1. For example, when A represents Pb and one additional element from Group IVA, the above general formula can be represented by the formula Cs(A 1-x A’ x )X3, where A represents Pb and A’ represents an additional element. Similarly, when X contains multiple types of halogens, the molar ratio of the halogen element to Cs is 3:1. Therefore, when the perovskite contains multiple halogens, the above general formula can be represented by the formula CsA(X 3-x X’ x )3, where X and X’ represent two different halogen atoms. Finally, when the perovskite contains one additional Group IVA element and two different halogen atoms, the above general formula can be represented by the formula Cs(A 1-x A’ x)(X 3-x X’ x ) can be represented by the formula, where A represents Pb, A’ represents an additional Group IVA element, and X and X’ represent two different halogen atoms.

[0037] The doped perovskite can be produced by forming a mixture of (a) a perovskite having the chemical formula CsAX3, the chemical formula RbAX3, or the chemical formula Cs 1-x RbxPbX3 (0 < x < 1) (where A represents Pb, Sn, Si, Ge, or a combination of two or more thereof, and X represents one or more halogen atoms); and (b) a compound serving as an oxygen dopant source and / or a compound serving as a fluorine dopant source. Then, this mixture is heated to form a melt, which is then crystallized. During the crystallization of the melt, oxygen atoms or fluorine atoms from the dopant source compound are incorporated into the perovskite crystal lattice, providing a perovskite doped with oxygen atoms and / or fluorine atoms. Therefore, this compound is a doped compound rather than a new alloy. Further, since the dopant is incorporated not only on the outer surface or surface of the particles of the polycrystalline material but also inside the crystal, the crystal is not only surface passivated by the dopant atoms. The doped perovskite may be a single crystal or a polycrystal. However, in either case, the dopant atoms are incorporated into the bulk lattice of the crystal. Furthermore, since the doping process does not depend on the diffusion of oxygen or fluorine into a pre-formed crystal, this process can provide uniform doping across the entire bulk of a large single crystal of perovskite, for example, across a crystal having a thickness of 0.1 mm, 0.5 mm, 1 mm, or more. The doped CsAX3, RbAX3, or Cs 1-x RbxPbX3 perovskite can be produced as a single crystallization product or in the form of a solid solution containing one or more homologues of CsAX3, RbAX3, or Cs 1-x RbxPbX3 perovskite.

[0038] Furthermore, the concentration of the dopant source compound in the mixture used to crystallize the perovskite is preferably low enough to avoid the precipitation of lead oxide, lead fluoride, or other dopant source compounds as a second phase in the crystallized doped perovskite; that is, the concentration of the dopant source compound is preferably low enough to produce a single-phase doped perovskite. The concentration of the dopant source compound that causes the precipitation of the second phase depends on the starting materials of the particular perovskite and the dopant source compound used, but generally, a concentration of 1 mol% or less of the dopant source compound is sufficient to prevent the formation of the second phase. This includes embodiments of the mixture in which the mol% of the dopant source compound is 0.5 mol% or less or 0.3 mol% or less, and further includes embodiments of the mixture in which the mol% of the dopant source compound is 0.1 mol% or less. For illustrative purposes only, a mixture having a dopant source concentration (e.g., PbO concentration or PbF2 concentration) in the range of approximately 0.01 mol% to 0.3 mol%, such as in the range of 0.02 mol% to 0.1 mol%, may be used.

[0039] Compounds that provide an oxygen or fluorine dopant source (referred to herein as “dopant source compound”) include CsAX3 or Cs 1-x Any lead-containing compound that can introduce oxygen or fluorine as an impurity into the lattice of the RbxPbX3 perovskite may be used. Examples of suitable oxygen dopant source compounds include lead oxides such as PbO, Pb3O4, and PbO2, as well as other compounds containing both lead and oxygen that decompose into lead oxide upon heating. Examples of compounds containing both oxygen and lead that decompose to produce lead oxide include Pb(OH)2, PbCO3, and Pb2(OH)2CO3. The compounds Pb(OH)2, PbCO3, and Pb2(OH)2CO3 are formed by the oxidation of other lead-containing compounds such as PbBr2. A single dopant source compound may be used, or a combination of two or more dopant source compounds may be used. Further examples of suitable fluorine dopant source compounds include lead fluoride such as PbF2, tin fluoride such as SnF2, and other compounds containing both lead and fluorine that decompose into lead fluoride upon heating.

[0040] Doped perovskites can be grown as large single crystals by solid-phase solidification methods, including the vertical Bridgman method, horizontal freezing method, Czochralski method, top-seed flux method, or narrow-band purification method, thereby reducing production costs and enabling the production of large-volume crystal boules. However, the growth method is not limited to solid-phase solidification. Other suitable methods include the low-temperature solution method, chemical vapor transport method, and physical vapor transport method. Depending on the growth method, doped perovskites can be grown as single crystals by solid-phase solidification without the use of flux, resulting in high impurity grades. However, solid-phase solidification may be carried out with the help of a flux to further lower the crystallization temperature.

[0041] Exogenous oxygen-doped and / or fluorine-doped CsAX3, RbAX3, or Cs as described herein 1-x Hard radiation detectors that utilize RbxPbX3 perovskite as a photoactive layer use intrinsic CsAX3, RbAX3, or Cs 1-x Compared to hard radiation detectors using RbxPbX3 perovskite as the photoactive layer, this doping improves energy resolution, the product of carrier mobility and lifetime, and / or compositional uniformity (yield). Furthermore, this doping can provide improved photoluminescence (PL) intensity and / or extended photoluminescence emission decay time (e.g., 100 ns or more) due to potentially doped-related improvements in lattice matching and carrier lifetime. While not intended to be bound by any particular theory of the present invention, it has been suggested that at least partially this improvement can be explained by a reduction in halogen atom (e.g., Cl and / or Br) vacancies in the crystal due to the incorporation of dopant atoms into the lattice. For example, photoluminescence decay times of at least 500 ns, at least 1000 ns, and at least 2000 ns can be provided. For example, decay times in the range of 500 ns to 2800 ns can be achieved. Such improvements can be achieved with, for example, CsAX3, RbAX3, or CsAX3. 1-xA perovskite can be realized in which the molar ratio of O impurities (i.e., oxygen atom dopants) or F impurities (i.e., fluorine atom dopants) to RbxPbX3 is 1 ppm or more, including, for example, 10 ppm or more and 100 ppm or more. For example, oxygen atom dopant and / or fluorine atom dopant concentrations in the range of about 1 ppm to 10,000 ppm may be used.

[0042] While not intending to be bound by any particular theory underlying the various inventions described herein, the inventors propose that doping of the perovskite passivates dominant deep energy levels that would otherwise trap electron-hole pairs and prevent the achievement of high yields and charge collection efficiencies. The inventors also propose that the dominant deep energy levels can be passivated or eliminated by extrinsic doping. As a result, extrinsic doping of the perovskite improves the compositional uniformity, improves the energy resolution, and enables a yield improvement of up to 80%.

[0043] An example of a hard radiation detector that can be fabricated using a doped perovskite includes the following components: (a) a photoactive layer comprising an oxygen-doped and / or fluorine-doped perovskite having the chemical formula CsAX3, the chemical formula RbAX3, or the chemical formula Cs 1-x RbxPbX3 (0 < x < 1) (where A represents Pb or a combination of Pb and one or more of Sn, Si, and Ge, X represents one or more halogen atoms, and further oxygen dopants and fluorine dopants are incorporated into the crystal lattice of the perovskite); (b) a first electrode in electrical communication with the photoactive layer and configured to apply an electric field across the photoactive layer; (c) a second electrode in electrical communication with the photoactive layer and configured to apply an electric field across the photoactive layer; and (d) a signal detector configured to measure the photocurrent generated within the photoactive layer when the photoactive layer is exposed to ionizing incident radiation.

[0044] When a doped perovskite absorbs incident radiation, electron-hole pairs are formed, generating a photocurrent. The apparatus may further include one or more additional electronic components configured to measure the photocurrent. The incident radiation may be particle radiation such as alpha particle radiation, or electromagnetic radiation such as gamma radiation (i.e., about 1 × 10⁻¹⁶). -10 ~about 2×10 -13 It may also include wavelengths in the range of m, and / or radiation in the X-ray region (i.e., X-ray energies in the range of 1 keV to 100 keV, which roughly correspond to wavelengths of 0.01 nm to 1 nm).

[0045] At least one of the first and second electrodes is preferably at least partially transparent to incident radiation. These electrodes may include, for example, a conductive oxide such as FTO, or a metal such as gold or aluminum. When the doped perovskite absorbs incident radiation, electron-hole pairs are formed and move toward the respective electrodes in the applied electric field. The photocurrents of electrons or holes can be measured separately by changing the bias direction. The apparatus may further include a signal amplifier for amplifying the photocurrent signal generated by the photodetector, a processor, a data storage unit (e.g., a computer-readable medium), and an output interface such as a computer interface. The computer-readable medium is, as those skilled in the art will know, an electronic storage location or memory unit for information that the processor can access. The computer-readable medium may include, but is not limited to, any type of random access memory (RAM), any type of read-only memory (ROM), any type of flash memory (such as magnetic storage devices, optical discs, digital multipurpose discs (DVDs), etc.), smart cards, flash memory devices, etc. The processor executes instructions that can be executed by a dedicated computer, logic circuits, hardware circuits, or other means. The processor may run in hardware and / or firmware. The processor executes instructions, meaning it performs / controls the operations invoked by those instructions. The term “execution” refers to the process of running an application, or carrying out the operations requested by an instruction. Instructions may be written using one or more programming languages, scripting languages, assembly languages, etc. The processor can be operably coupled to a computer-readable medium and output interface configured to receive, transmit, display, and / or otherwise process signals generated by a photodetector. For example, the processor, computer-readable medium, and output interface may be configured to produce a graphical representation of the measured photocurrent. [Examples]

[0046] This example includes oxygen-doped CsPbBr3 and oxygen-doped CsPbBr, which use PbO as the dopant source compound. 3-x Cl x This paper also describes the growth of fluorine-doped CsPbBr3. Furthermore, it describes the use of oxygen-doped CsPbBr3 as a photoactive layer in hard radiation detectors. Experimental section

[0047] Reagents: The chemicals used in this invention include: (1) CsBr powder, 99.999% purity, Alfa Aesar; (2) PbBr2, 99.999% purity, Alfa Aesar; (3) PbO powder, 99.999% purity, Alfa Aesar; (4) Lead rod, 99.999% purity, Alfa Aesar. This sample was left in the air for one month until the glossy metal surface turned gray; (5) PbO2 powder, 99.999% purity, Alfa Aesar; and (6) Photodegraded PbBr2 powder. White 5N purity PbBr2 powder was left in the air and irradiated with an incandescent lamp for two weeks until it turned dark.

[0048] Synthesis, Purification, and Crystal Growth: Polycrystalline CsPbBr3 raw materials were synthesized by directly chemically reacting 106.405 g of CsBr (0.50 mol) and 183.505 g of PbBr2 (0.50 mol) precursors in a 1:1 stoichiometric ratio within a 22 mm inner diameter quartz glass tube, after sealing them with a flame under vacuum. This synthesis was carried out in a temperature-programmed oscillating furnace at 650°C. o The reaction was carried out at C for 48 hours to ensure complete reaction, and then allowed to rise to room temperature for 20 minutes. o The mixture was gradually cooled at a rate of C / cm. The resulting ternary product was not subjected to any purification treatment. After synthesis, 25 g of CsPbBr3 starting material containing specific concentrations of PbO as the dopant source compound was placed in quartz ampoules with a thickness of 1.5 mm and an inner diameter of 10 mm, each with a conical tip. The concentration of PbO, the dopant source compound added to the CsPbBr3 starting material, was varied in molar ratio to 0.00%, 0.01%, 0.05%, 0.10%, 0.30%, 0.50%, and 1% (i.e., 0.01 mol% to 1 mol%). Subsequently, these ampoules were subjected to 3 × 10⁻⁶-4 The tube was sealed under a vacuum of mbar. Crystal growth was carried out in a vertical Bridgman furnace in three temperature zones (Bridgman, PW et al., Proceedings of the American Academy of Arts and Sciences 1925, 60 (6), 305-383). Before actual crystal growth, the tube was left still in the high-temperature zone of the Bridgman furnace for 12 hours to ensure complete dissolution. Subsequently, the ampoule was moved at a slow speed of 0.5 mm / h and approximately 5.1 o With a temperature gradient of C / cm, in the high-temperature region (580 o C) to the intermediate range (500 o Up to C, and in the low temperature range (380 o Moved down to C). After the entire melt of CsPbBr3 had completely crystallized, the ampoule was 5 o The samples were cooled to room temperature at an increased descent rate of 5.0 mm / h to generate a cooling rate of C / h. All six boules, prepared using dopant source compounds of varying concentrations, were grown one by one under the same furnace at the same temperature setting and transfer rate.

[0049] Crystallization and Characterization: New boules grown in the furnace were cut perpendicular to the growth direction using a diamond saw. The section was cut from the front to the rear end of the boule and polished with 800-grit silicon carbide sandpaper. A final polishing was performed using a cloth to obtain a very smooth wafer. PXRD analysis of the polished samples from the crystal was performed using a CPS 120 INEL diffractometer (Cu-Ka graphite monochromatic radiation, λ=1.5418 Å) calibrated for NIST silicon, operating at 40 kV / 20 mA and equipped with a position-sensing detector with a planar sample shape. A simulated powder pattern was calculated from single-crystal X-ray data using the PowderCell software package (Kraus, WN, G, PowderCell 2.3 1998).

[0050] X-ray photoelectron spectroscopy: X-ray photoelectron spectroscopy (XPS) measurements were performed using a Thermo Scientific ESCALAB 250 Xi spectrometer equipped with a monochromatic Al Kα X-ray source (1486.6 eV) operating at 300 W. The sample was placed under ultra-high vacuum (P<10 -8 Analysis was performed at a transfer energy of 150 eV (surface scan) or 25 eV (high-resolution scan) under mbar. All peaks were calibrated by the binding energy of the C 1s peak at 284.7 eV with exogenous carbon. In CsPbBr3 crystals, a newly cleaved exposed surface from a thick crystal was used for measurement to remove absorbed water and carbon dioxide from the surface, and the exposed surface was ion-milled (Ar + Further etching was performed using ions. For oxidized Pb metal and photodegraded PbBr2 samples, surface etching was not performed because we were focusing on the oxide layer on their surfaces.

[0051] Device fabrication: Dimensions approximately 5 x 5 mm 2 Furthermore, a polished CsPbBr3 wafer with a thickness of 1.00 mm was selected, and a detector was fabricated on the surface of a glass substrate. The resistivity of CsPbBr3 is approximately 10 10 The resistance (Ω·cm) was not high enough to suppress the background signal from the dark current, so a Schottky junction was used to further suppress the dark current from background holes. Since the conduction type of the CsPbBr3 crystal is p-type, a Ga junction with a low work function was selected to construct a Schottky junction that prevents hole injection from the junction into the semiconductor. Accordingly, the upper and lower electrodes were fabricated by coating them with Ga liquid metal and a fast-drying Au paint, respectively. This device operates with a reverse bias voltage when hard radiation is detected and leakage current is suppressed. A glass substrate with a Cu foil piece was used as the sample holder, and the Cu foil piece was coupled to the wafer electrode using a Cu wire with a diameter of 0.1 mm.

[0052] Charge transport measurements: Current-voltage (IV) measurements were performed in a dark environment using direct current (DC) to evaluate leakage current and estimate resistivity. DC conductivity was measured using a Keithley 6517B voltmeter and a Keithley 6105 resistor adapter. Electromagnetic interference and photoconductive response were eliminated by a metal enclosure.

[0053] Hard radiation spectroscopy: The spectral response of a 1.00 mm thick CsPbBr3 detector was measured using a homemade system including an eV-550 preamplifier box, a spectroscopic amplifier (ORTEC, Model 572A), and a computer-mounted multi-channel pulse height analyzer (Model ASPEC-927). The final signal was loaded into MAESTRO-32 software. Gamma-ray spectroscopy was performed in air. 57 The distance between the Co radiation source (approximately 0.05 mCi) and the detector was set to approximately 12 cm. The optimal linear amplifier gain, amplifier shaping time, and recording time were set to 100, 2.0 μs, and 300 s, respectively. Without a radiation source, pulsed gamma-ray wave height spectra obtained by applying a bias voltage were collected as background noise under the same experimental conditions. In measurements under hole transport, the incident gamma rays passed through the grounded Ga junction. The Au junction for charge collection was connected to the negative bias to ensure that the Schottky junction functioned reliably under reverse bias. In measurements under electron transport, the incident gamma rays passed through the grounded Au junction. The Ga junction for charge collection was connected to the positive bias to ensure that the Schottky junction functioned reliably even under reverse bias.

[0054] Approximation of the product of carrier mobility and lifetime: The most important performance index for evaluating the performance of semiconductor detector materials with respect to radiation detection efficiency is the product of carrier mobility and lifetime, i.e., μτ. In measuring the product of carrier mobility and lifetime, the product was estimated from the voltage dependence of the gamma-ray spectrum using an apparatus similar to that described by A. Many and further developed by Ruzin et al. (Many, A., J Phys Chem Solids 1965, 26 (3), 575-578; and Ruzin, A. et al., J. Appl. Phys. 1997, 82 (9), 4166-4171). The product of electron mobility and lifetime was derived from the analysis of charge collection efficiency (CCE) at each bias voltage applied to the sample. The charge collection efficiency (CCE) correlated with the parameter V, which is the bias voltage applied to the sample, according to the following equation 1: Hecht equation for a single carrier.

number

[0055] Measurement of photoluminescence and time-resolved photoluminescence decay time: Spectral and time-resolved measurements were performed at room temperature on freshly cleaved, unpolished CsPbBr3 crystals using an Edinburgh Instruments FS5 spectrofluorometer. The FS system consisted of an EPL405 pulsed diode laser excitation source with a wavelength of 405 nm, lifetime selection using time-correlated single-photon counting (TCSPC) technique, and a photomultiplier tube (PMT) 980 detector. The CsPbBr3 crystal was mounted in the SC-10 sample holder module. The emission slit width was set to 0.5 nm. A 495 nm long-pass filter was used in the emission path to the detector. PL data were collected from the emission range of 400–800 nm at 1 nm intervals and with a residence time of 0.5 seconds. For PL decay time measurements, each decay was fitted to a combination of two or three stretching indices using the FAST software package. The measured damping curve was fitted to the sum of the exponential functions in Equation 2 below.

number

[0056] Crystal Growth and Compositional Analysis: Crystal growth was carried out in a vertical Bridgman furnace in three temperature ranges. Figure 1A shows the temperature characteristics of the furnace along its longitudinal direction, providing a temperature gradient of 5.1 °C / cm and a growth rate of 0.5 mm / h for crystallization. The yellow deposits observed on the top of the boules were due to vapor transport of CsPbBr3 during the cooling process of the ampoule. All boules were transparent, crack-free, and orange in color, corresponding to the band gap of CsPbBr3 at 2.25 eV. Boules produced using PbO concentrations of 0.50% and 1.00% adhered to the inner wall of the molten ampoule, producing PbSiO3 through the reaction of excess dopant source compound PbO with molten silica. The occurrence of adhesion to the tube indicates that the equilibrium solid solution state of the dopant source compound PbO in the CsPbBr3 lattice needs to be less than 0.50%. As shown in Figure 1B, compositional analysis of all Boule's ground samples by PXRD clearly shows that no phase other than CsPbBr3 was detected. 10 Due to the insufficient resistivity of Ω·cm, a lower work function Ga liquid metal was selected as the contact to construct a Schottky junction, preventing hole injection from the contact to the semiconductor and further reducing the dark current. An Au paint with a higher work function was selected as the contact to form an ohmic contact with the semiconductor. Figure 1C shows the current-voltage (IV) characteristics at room temperature for crystals from all six Boules fabricated using various PbO concentrations. All IV curves show typical rectification function, indicating that the Ga contact formed a Schottky junction with the CsPbBr3 semiconductor. All dark currents under reverse bias voltage could be controlled to a low level of less than 10 nA at -100 V, which is low enough to obtain a gamma-ray response with a high signal-to-noise ratio when the instrument detects gamma rays.

[0057] Improved detection performance: The detector, made from CsPbBr3 crystals produced using various PbO concentrations, detects 0.05 mCi 57The pulse height spectra of 122 keV gamma rays from a Co radiation source were measured. Figure 2A shows the gamma-ray spectral response from a planar apparatus made from undoped CsPbBr3 crystals in a hole-collecting configuration (anodic irradiation) with an applied voltage of -200 V. This apparatus showed a weak optical response in counting mode because it could distinguish the signal from background noise. However, this apparatus could not resolve gamma rays. Figure 3A shows the pulse height spectra for 122 keV gamma rays in a hole-collecting configuration of a planar apparatus made from CsPbBr3 crystals prepared using various concentrations of PbO as the dopant source compound. All samples prepared using PbO as the dopant source compound allowed observation of the optical peak at all energies, thus resolving the 122 keV gamma rays. As shown in Table 1, the energy resolution achieved a maximum of 4.1% when using a 0.01% concentration of PbO as the dopant source compound, and then gradually decreased to 19.0% at a PbO concentration of 1.0%, indicating that the optimal concentration of PbO for achieving the best energy resolution is around 0.05%. As shown in Figure 2B, assuming a decrease in hole collection efficiency, the number of peak channels of the total energy light peak decreased with increasing PbO concentration. Excess PbO may not be incorporated into the lattice of CsPbBr3. Conversely, excess PbO may exist as a second phase in the crystal, functioning as a carrier scattering center and consequently reducing the hole collection efficiency. The most important figure of merit for evaluating the performance of semiconductor detection materials with respect to radiation detection efficiency is the product of carrier mobility and lifetime, i.e., μτ. Figure 2C shows the hole collection efficiency as a function of applied voltage. The product of hole mobility and lifetime of oxygen-doped perovskite produced using 0.05% PbO, i.e., μ h τ h is 1.0 × 10 -3 cm 2 When the maximum value of / V is achieved and PbO is used as a dopant source at a concentration of 1.00%, the result is 1.7 × 10⁻⁶. -4 cm 2 The value gradually decreased to the minimum value of / V (Figure 2D). This trend is in good agreement with the trend of the gamma ray energy resolution. Notably, the μ of the hole at a concentration of 1.00% h τh This is far higher than the solid solubility limit of PbO in the CsPbBr3 lattice, where the PbO concentration is thought to be lower than 0.50%, even though 10 -4 cm 2 It maintained a level of / V. In summary, oxygen doping using PbO compounds as an oxygen dopant source generates energy resolution and μ h τ h This will lead to a significant improvement.

[0058] Furthermore, the detection performance under an electron collection configuration (cathode irradiation) was measured and evaluated. Figure 3A shows the gamma-ray spectral response from a planar apparatus prepared from an oxygen-undoped CsPbBr3 crystal under an electron collection configuration with an applied voltage of +400V. In this apparatus, gamma rays were detected in counting mode without energy resolution. However, a sample prepared using 0.05% PbO as the oxygen dopant source showed an energy resolution of 11.3% and 6.2 × 10⁻⁶ -4 cm 2 The 122 keV gamma rays could be resolved by the product of the electron mobility and lifetime of / V. The result for a sample prepared using 0.05% PbO as the dopant source was 1.0 × 10⁻⁶. -3 cm 2 Compared to the product of hole mobility and lifetime at / V (Figures 3B and 3C), electron transport is inferior to hole transport, indicating that hole transport is dominant in the CsPbBr3 material. Similar to the tendency for the product of hole mobility and lifetime to decrease with increasing dopant source compound concentration, the product of electron mobility and lifetime also decreased to 6.2 × 10⁻¹⁰ at a dopant source compound concentration of 0.05%. -4 cm 2 9.0 × 10⁻⁶ at a dopant source compound concentration of 1.00% from / V -5 cm 2 It gradually decreased to / V.

[0059] [Table 1]

[0060] Improved Yield: Oxygen doping with trace amounts of PbO, a dopant source compound, not only significantly improved detection performance but also increased the yield of crystals grown by the Bridgman method. Figures 4A-4C show the pulse height spectra (hole collection) of 122 keV gamma rays from a planar apparatus prepared from CsPbBr3 crystals extracted from the front (Figure 4A), middle (Figure 4B), and rear (Figure 4C) ends of a Boule crystal prepared using a 0.10% concentration of PbO as the dopant source compound. All three samples resolved 122 keV gamma rays with an energy resolution in the range of 5.8%-7.8%, indicating high compositional uniformity along the growth direction of the Boule crystal in terms of detection performance. The overall yield increased to approximately 80% with oxygen doping. Oxygen doping allows for the introduction of O impurities with a uniform distribution within the lattice, which is thought to insulate electron-hole pairs that are trapped / annihilated at major deep energy levels.

[0061] XPS Analysis: Oxygen doping introduces oxygen impurities into the CsPbBr3 lattice, and it is hypothesized that this doping leads to the passivation of major deep energy levels. To confirm the possibility of O impurity incorporation into the lattice, XPS analysis was performed on the O 1s bond energy. As shown in Figures 5A-5D and Table 2, compared to the bond energies of Br 3d, Pb 3d, and Cs 4d electrons in undoped CsPbBr3, the samples prepared using 0.05% PbO as the dopant source compound showed almost identical bond energies for these electrons. However, in the oxygen-doped samples, a signal for O 1s was observed that was not observed in the undoped samples, clearly indicating the presence of O impurities in the oxygen-doped samples. The bond energy of the O 1s electron in the oxygen-doped samples (533.0 eV) differs from that of the samples prepared using PbO as the dopant source compound, indicating that the oxygen impurities present in the oxygen-doped samples are not the PbO phase. The bond energy of the 1s electrons of O in the oxygen-doped sample (533.0 eV) is very close to that of H2O (533.1 eV), so one possibility is that surface moisture is attributable to the 533.0 eV peak. However, if the XPS scan is performed using Ar +Considering that the ion etching was performed on a newly cleaved surface, this possibility can be ruled out. Therefore, the 533.0 eV can be determined to be due to O impurities incorporated into the CsPbBr3 lattice, and not to PbO or surface-absorbed moisture.

[0062] As shown in Figure 5C, the broad signal peak of O 1s electrons in oxygen-doped CsPbBr3 prepared using PbO as a dopant source can be split into two separate peaks with bond energies of 529.7 eV and 527.8 eV, respectively. These two peaks may be attributed to O 1s electrons from the orthorhombic phase (high-temperature phase) and the tetragonal phase (room-temperature phase), respectively. These two different O 1s bond energies clearly indicate that PbO is a mixture of orthorhombic and tetragonal phases. Thus, the phase of PbO is not limited to the orthorhombic phase alone.

[0063] [Table 2]

[0064] It was confirmed that oxygen doping significantly improves detection performance. Therefore, the range of effective dopant source compounds was expanded from PbO to any material that contains PbO or decomposes to PbO upon heating. Figure 6A shows the X-ray photoelectron spectrum of O 1s electrons from oxidized Pb metal. The signal peak can be split into two peaks at 529.4 eV and 527.7 eV, respectively. The 529.4 eV peak may be due to orthorhombic PbO, and the 527.7 eV peak may be due to PbO2. Based on these results, the oxidized surface layer of the Pb metal was composed of PbO and PbO2. Figure 6B shows the X-ray photoelectron spectrum of O 1s electrons from dark PbBr2 powder. The signal peak can be split into two peaks at 532.7 eV and 531.3 eV, respectively. The peak at 532.7 eV may be due to the Pb-O bond in PbCO3, and the other peak may be due to the OH bond in Pb(OH)2. Therefore, the dark surface layer of PbBr2 may contain a mixture of PbCO3, Pb(OH)2, and Pb2(OH)2CO3, all of which produce Pb oxides when heated. Thus, the range of effective dopant source compounds in this invention has been expanded from PbO to PbO2, Pb3O4, PbCO3, Pb(OH)2, and Pb2(OH)2CO3, which can produce PbO when heated.

[0065] Improved Photoluminescence: PL spectroscopy was performed to investigate the lattice coherence of the grown crystals and to determine the presence or absence of any radioactive defects. Figure 7A shows the PL spectrum of an undoped sample at room temperature using a blue laser with an output of 0.5 mW and a wavelength of 405 nm. The undoped sample showed weak PL emission with a peak at 524.0 nm, which may be due to intrinsic bandgap emission from CsPbBr3. This weak emission was not visible to the naked eye. The spectrum was accompanied by broad defect-related emission starting at 600 nm, revealing that specific defects function as major trapping and recombination centers for photo-induced electron-hole pair emission. Figure 7B shows the PL spectrum from an oxygen-doped sample under the same experimental conditions. The approximate peak intensity of the sample prepared using a 0.05% concentration of PbO as the dopant source compound was improved to a maximum of 217 times higher than that of the undoped sample (Table 3). Most importantly, no widespread defect-related emission was observed in any spectrum from the oxygen-doped sample, indicating the absence of radioactive defects present in the undoped sample. The green PL emission was very strong and could be observed with the naked eye. As shown in Figure 7C, the PL intensity gradually decreased as the concentration of PbO as the dopant source compound increased. Notably, the PL intensity was 10 for perovskites prepared using the highest concentration of PbO as the dopant source, 1.00%. 5 The intensity remained stable, but it was still an order of magnitude higher than that of the undoped sample. Compared to the peak position of the undoped sample (524.0 nm), all emission peaks of the oxygen-doped sample had shifted to the red side at 533.6 nm. The shift of the main emission peak of the oxygen-doped sample to the red side and the significant improvement suggest that the emission may originate from exciton emission, which suggests that the carrier-to-photon conversion efficiency is much higher than that of bandgap emission.

[0066] PL decay time measurement is a powerful method for indicating whether carrier lifetimes are long or not, thereby sequentially evaluating the lattice integrity of the material. Figure 7D shows the time-resolved PL decay spectrum of emission at 524.0 nm for an undoped sample. This PL decayed dramatically to the point where its signal hardly exceeded the signal from the instrument response. As shown in Table 3, the average decay time was approximately 1.6 ns. Figure 7E shows the time-resolved PL decay spectra of emission at 533.6 nm for samples doped with various concentrations of PbO. The sample prepared with a PbO concentration of 0.05% showed the longest average decay time of 2689 ns (Figure 7F), which is in good agreement with the best carrier mobility-life product at this PbO concentration. The average PL decay time decreased with increasing PbO concentration. The decay time decreased to a minimum of 49 ns at a PbO concentration of 1.00%. Higher PbO concentrations may introduce more trapping and scattering centers, potentially shortening carrier lifetimes.

[0067] [Table 3]

[0068] To determine whether the radioactive transition after oxygen doping originated from exciton emission, the excitation intensity dependence of PL emission to the emission of perovskite with 0.05% PbO was measured at laser powers in the range of 0.25–5 mW (Figures 8A–8F). The intensity of each peak steadily increased with increasing laser power. All emission peaks could be split into two separate peaks (peak 1 and peak 2) by Gaussian fitting. The peak positions of peaks 1 and 2 did not shift when the laser power was changed. Table 4 shows the peak positions and intensities of peaks 1 and 2 at various laser powers.

[0069] The increase in PL intensity I with increasing excitation intensity L follows a power law dependence, governed by the exponent k (I~L). kIt has. In the case of excitation by photon energy greater than the bandgap energy, the value of the gradient k generally falls within either the range 0 < k < 1 or 1 < k < 2. In the case of 0 < k < 1, the emission band was due to recombination of donor-acceptor pairs (DAP) or free-bound-radiative recombination. In the case of 1 < k < 2, the emission was due to either free exciton transition or bound exciton transition. The coefficient k is the gradient of the logarithm of (PL intensity) versus the logarithm of (laser output) in the linear range, and at the two peaks, k values of 1.52 ± 0.08 and 1.54 ± 0.08 were found at peak 1 and peak 2, respectively (Figure 9). Peaks 1 and 2 fall within the range of free exciton transition or bound exciton transition. Considering that peak 1 has a higher peak energy, a narrower FWHM, and a higher intensity than peak 2, peaks 1 and 2 may be due to free exciton emission and bound exciton emission.

[0070] In summary, oxygen doping not only reduced the radiative defects associated with extensive defect luminescence in the undoped sample but also caused a transitional change from bandgap luminescence to exciton luminescence due to higher lattice perfection.

[0071]

Table 4

[0072] Further examples are shown in Figures 10, 11, and 12. In these examples, oxygen-doped CsPbBr 3-x Cl x was fabricated using PbO as the dopant source, and the properties of the doped perovskite were measured according to the above procedure. CsPbBr 3-x Cl xThe oxygen-doped mixed halide crystals of type 10A and 10B showed good energy resolution for gamma rays. CsPbBr2Cl crystals doped with various amounts of PbO showed stronger PL than their undoped counterparts, and mixed perovskites doped with 0.2% PbO as an oxygen dopant source showed stronger PL than mixed perovskites doped with 1% PbO (Figure 10). Figures 11A and 11B show the PL lifetimes of two different oxygen-doped samples of CsPbBr2Cl, which can be controlled by the amount of PbO dopant source added. Figure 12 shows the gamma-ray spectra obtained from two different oxygen-doped samples of CsPbBr2Cl, and the spectral resolution can be controlled by the amount of PbO dopant source added. As another example, Figure 13 shows CsPbBr2Cl doped with a PbO oxygen dopant source. 3-x I x The sample is shown below. Figure 13 shows oxygen-doped CsPbBr decomposing the 122 keV g-ray energy of a 57-Co source. 2.83 I 0.17 A radiation detector fabricated from this sample is shown. The sample was doped with a 0.5% PbO concentration.

[0073] Fluorine atom doped CsPbBr3 and CsPbBr 3-x Cl x Furthermore, the materials were manufactured and characterized using the methods described herein, but PbO was replaced with PbF2 as the dopant source. Fluorine was CsPbBr 3-x Cl x and CsPbBr 3-x I x This can be used as a beneficial dopant in materials. Figure 14A shows the PL lifetime of a fluorine-doped CsPbBr3 sample, demonstrating that the PL lifetime can be significantly increased compared to the undoped CsPbBr3 material (Figure 14B).

[0074] Synthesis, Purification, and Crystal Growth: Polycrystalline CsPbBr3, doped with fluorine using PbF2 as the dopant source, was synthesized by directly chemically reacting CsBr and PbBr2 precursors in a stoichiometric molar ratio of 1:1 in a fused silica tube with an inner diameter of 22 mm, sealed by a flame under vacuum. The total amount of CsBr and PbBr2 combined was 85 g. This synthesis was carried out in a temperature-programmed oscillating furnace at 650°C for 48 hours to ensure complete reaction, after which it was gradually cooled to room temperature at a rate of 20°C / cm. The resulting ternary product was not subjected to any purification treatment. After synthesis, various concentrations of PbF2 were added as dopant source compounds at 0.01 to 1 mol%. CsPbBr3 and PbF2 were each packed into quartz ampoules with a thickness of 1.5 mm and an inner diameter of 10 mm, with a conical tip. Subsequently, these ampoules were subjected to 3 × 10⁻⁶ -4 The samples were sealed under a vacuum of mbar. Crystal growth was carried out in a vertical Bridgman furnace at three different temperature ranges (Bridgman, PW et al., Proceedings of the American Academy of Arts and Sciences 1925, 60 (6), 305-383). Before actual crystal growth, the tubes were left stationary in the high-temperature range of the Bridgman furnace for 12 hours to ensure complete melting. Subsequently, the ampoules were moved downwards from the high-temperature range (580°C) to the intermediate range (500°C) and then to the low-temperature range (380°C) at a slow transfer rate of 0.5 mm / h and a temperature gradient of approximately 5.1 °C / cm. After the entire CsPbBr3 molten state had completely crystallized, the ampoules were cooled to room temperature at a faster descent rate of 5.0 mm / h to produce a cooling rate of 5 °C / h. All six boules prepared using dopant source compounds of varying concentrations were grown one by one in the same furnace at the same temperature settings and transfer rates.

[0075] The presence of oxygen and fluorine dopants in the perovskite crystals described herein may be detected by XPS analysis, secondary ion mass spectrometry (SIMS), and gaseous gas analysis (IGA), which can measure the levels of O and F present in the solid material from ppm to %.

[0076] As used herein, the term “exemplary” means an example, illustration, or demonstration. Any aspect or design described herein as “exemplary” should not necessarily be construed as being preferable or beneficial to any other aspect or design. Furthermore, for the purposes of this disclosure, unless otherwise specified, “a” or “an” may mean “one or more” or “one,” encompassing both embodiments.

[0077] The above-mentioned exemplary embodiments of the Invention have been presented for illustrative and explanatory purposes. This description is not intended to be exhaustive or to limit the Invention to the exact form of the disclosure, and modifications and changes may be possible in light of the above teachings or obtained from the practice of the Invention. The embodiments have been selected and described to illustrate the principles of the Invention and as practical applications of the Invention, so that those skilled in the art can utilize the Invention in various embodiments and make various modifications to suit specific conceivable uses. The scope of the Invention is intended to be defined by the appended claims and their equivalents.

Claims

1. Chemical formula CsAX 3 , chemical formula RbAX 3 , or chemical formula Cs 1-x Rb x PbX 3 (where 0 < x < 1, A represents Pb or a combination of Pb and one or more of Sn, Si, and Ge, and X represents one or more halogen atoms); and A doped perovskite comprising an oxygen atom dopant or a fluorine atom dopant in the crystal lattice of the perovskite single crystal.

2. The doped perovskite according to claim 1, comprising the oxygen atom dopant.

3. The aforementioned doped perovskite is oxygen-doped CsPbBr 3 The doped perovskite according to claim 2.

4. The oxygen-doped CsPbBr 3 The doped perovskite according to claim 3, having an oxygen dopant concentration in the range of 1 ppm to 10,000 ppm.

5. The doped perovskite according to claim 1, wherein the doped perovskite has an oxygen atom dopant concentration or a fluorine atom dopant concentration in the range of 1 ppm to 10,000 ppm.

6. The doped perovskite according to claim 1, comprising the fluorine atom dopant.

7. A device for detecting incident radiation, Chemical formula CsAX 3 、Chemical formula RbAX 3 、or chemical formula Cs 1-x Rb x PbX 3 (where 0 < x < 1, A represents Pb or a combination of Pb and one or more of Sn, Si, and Ge, and X represents one or more halogen atoms), a perovskite single crystal having the same, and a photoactive layer containing an oxygen atom dopant or a fluorine atom dopant in the crystal lattice of the perovskite single crystal; A first electrode configured to be electrically in communication with the photoactive layer and to apply an electric field to the entire photoactive layer; A second electrode configured to be electrically in communication with the photoactive layer and to apply an electric field to the entire photoactive layer; and An apparatus comprising a signal detector configured to measure a photocurrent generated within a photoactive layer when the photoactive layer is exposed to incident X-rays, gamma rays, and / or alpha particles.

8. A computer-readable medium operably coupled to the signal detector and configured to store photocurrent data; and The apparatus according to claim 7, further comprising a computer interface operably coupled to the computer-readable medium and configured to generate a graph display of the photocurrent data.

9. The apparatus according to claim 7, wherein the doped perovskite comprises the oxygen atom dopant.

10. The aforementioned doped perovskite is oxygen-doped CsPbBr 3 The apparatus according to claim 9.

11. The apparatus according to claim 10, wherein the doped perovskite has an oxygen atom dopant concentration in the range of 1 ppm to 10,000 ppm.

12. The apparatus according to claim 7, wherein the photoactive layer comprises only a single perovskite phase.

13. The apparatus according to claim 7, wherein the doped perovskite comprises the fluorine atom dopant.

14. A method for detecting incident radiation using the apparatus described in claim 7, A step of exposing the photoactive layer of the apparatus to incident radiation including X-rays, gamma rays, and / or alpha particles, thereby causing the oxygen-doped perovskite or fluorine-doped perovskite to absorb the incident radiation and generate a photocurrent within the material; and A method comprising the step of detecting the photocurrent and measuring at least one of the energy and intensity of the absorbed incident radiation.

15. Chemical formula CsAX 3 A method for producing an oxygen-doped perovskite or a fluorine-doped perovskite having (wherein A represents Pb or a combination of Pb and one or more of Sn, Si, and Ge, and X represents one or more halogen atoms), Chemical formula CsAX 3 、chemical formula RbAX 3 、or chemical formula Cs 1-x Rb x PbX 3 (where 0 < x < 1, A represents Pb, Sn, Si, Ge, or a combination of two or more thereof, and X represents one or more halogen atoms), and a perovskite having PbO, a compound containing lead and oxygen that decomposes into PbO upon heating, PbF 2 、or a dopant source compound containing a compound containing lead and oxygen that decomposes into PbF 2 upon heating to produce a mixture thereof; A step of melting the perovskite and the dopant source to produce a melt; and A method comprising the step of crystallizing an oxygen-doped perovskite or a fluorine-doped perovskite from the melt.

16. The method according to claim 15, wherein the doped perovskite has an oxygen atom dopant concentration or a fluorine atom dopant concentration in the range of 1 ppm to 10,000 ppm. 。

17. The method according to claim 15, wherein the concentration of the dopant source compound in the mixture is in the range of 0.01 mol% to 1 mol%.

18. The perovskite is CsPbBr 3 The method according to claim 15.

19. The method according to claim 16, wherein the perovskite is an oxygen-doped perovskite, and the dopant source compound comprises PbO.

20. The perovskite is an oxygen-doped perovskite, and the dopant source compound is PbO 2 Pb 3 O 4 Pb(OH) 2 PbCO 3 Pb 2 (OH) 2 CO 3 The method according to claim 15, or a combination of two or more of them.

21. The perovskite is a fluorine-doped perovskite, and the dopant source compound is PbF 2 The method according to claim 15, including the method described in claim 15.

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