Perovskite composition with a functionalized surface for radiation detection

Abstract

The invention relates to a composition comprising a plurality of distinct particles, wherein at least one particle comprises: a core of a first three-dimensional perovskite material of chemical formula ABX3; a coating of a second two-dimensional perovskite material of chemical formula RA'N-1B'NX'3N+1 or R2A'N-1B'NX'3N+1 disposed on an outer surface of the core; A and A' each being selected from a first group of cations or an alloy of elements from the first group of cations; B and B' each being selected from a second group of inorganic cations or an alloy of elements from the second group of inorganic cations; X and X' each being selected from a group of halogens or an alloy of elements from the halogen group; R being selected from a third group of organic cations or an alloy of elements from the third group of organic cations. Figure for the abstract: Fig. 1

Description

Title of the invention: Perovskite composition with a functionalized surface for radiation detection Scope

[0001] The present invention relates to the field of electronic and optoelectronic devices for the detection of ionizing radiation such as X-rays, gamma rays, alpha and beta charged particles, and neutrons. More particularly, the invention relates to radiation absorption structures based on pressed perovskite particles. Technical problem

[0002] The relevant technical field is the development of radiation detection devices capable of generating electrical charge carriers from incident photons or particles. Generally, a radiation detection device comprises an absorption structure confined between two electrodes. The semiconductor absorption structure converts the incident radiation into negative charge carriers ("electrons") in the conduction band and positive charge carriers ("holes") in the valence band. The materials used to fabricate the absorption structure and its thickness determine the proportion of radiation absorbed according to its energy. In the context of the invention, a radiation detection device is understood to be a structure capable of converting ionizing radiation into an electronic signal readable by a readout circuit.The term ionizing radiation covers, for example, X-rays, gamma rays, alpha and beta charged particles, and neutrons.

[0003] Devices for the direct detection of ionizing radiation (X-rays) require absorption structures with larger lateral dimensions (width, length) compared to most other optical detection devices. Conventional materials used to fabricate absorption structures in this field are either incompatible with these large dimensions and reasonable manufacturing costs (single-crystal CdxZni xTe or CdTe, for example), or have limited absorption at the high energies required for general radiography (amorphous selenium, for example).

[0004] In this context, perovskites in powder or sintered form offer emerging solutions for fabricating absorption and conversion structures in optoelectronic devices. This type of material allows for the fabrication of absorption structures by compressing the perovskite powder. The powders used in known solutions are composed of particles (or grains) in three-dimensional perovskites. A 3D perovskite is a perovskite-based crystalline material with a three-dimensional structure. This means that the atoms in the crystal structure are arranged uniformly in three-dimensional space. 3D perovskites can take the form of bulk crystals or crystalline powders. The crystallographic structure of a 3D perovskite is a typical crystal structure observed in certain materials that follow the general chemical formula ABX3, where "A" is a cation, B is a cation, and "X" is an anion, often of the halide type (Cf, Br, I). The crystal lattice is formed by a plurality of octahedra arranged periodically. Each cation B is surrounded by six anions X, forming an octahedron, called BX6. This octahedron is the basic building block of the 3D perovskite structure. Each BX6 octahedron shares all its vertices with other adjacent octahedrons.Thus, in a unit cell of the perovskite structure: each vertex of the octahedron is occupied by an anion X; each anion X is shared between two adjacent octahedra, and each cation A is located in a space bounded by eight adjacent octahedra. The 3D perovskite then constitutes a continuous, three-dimensional space arranged periodically, formed by the arrangement described.

[0005] However, in the context of 3D perovskite-based radiation detectors, a technical problem arises concerning the minimization of dark current. Dark current represents the residual electrical flux through the detection device in the absence of radiation and in darkness. High dark currents generate background noise that hinders the detection of radiation fluxes below a certain threshold, while also limiting the sensor's dynamic range. 3D perovskite-based detectors typically exhibit dark currents on the order of pA / cm². For certain applications, such as flat panels used in medical radiography, technical specifications require dark currents on the order of nA / cm², which is three decades lower than the values ​​obtained with state-of-the-art solutions.Therefore, it is necessary to find solutions to minimize dark current in perovskite detectors in order to meet the increasing performance and accuracy requirements in various application areas.

[0006] By way of example, when used as an X-ray imager for medical radiography, the dark current fills the storage capacity of the pixels, thus limiting the maximum X-ray dose that each pixel can receive and reducing the detector's dynamic range. Furthermore, being a source of noise, it limits the visibility of image details at low X-ray doses, for example, in X-ray surgery. If the average value of the dark current fluctuates over time, additional noise appears, limiting the visibility of details even at higher doses, thus requiring an increase in the X-ray dose administered to the patient. Moreover, if These fluctuations are not uniform across the entire imager surface; artifacts can appear in the image, thus distorting the diagnosis. It is therefore essential that the dark current be low while maintaining good sensitivity to obtain a good signal-to-noise ratio from the detector.

[0007] It is noted that the value of the dark current in optoelectronic devices depends on several factors, including the phenomena of ion migration from the electrodes into the absorption structure.

[0008] Another problem encountered in 3D perovskite-based radiation detectors is the instability of their electrical performance over time. "Electrical stability" refers to the detector's ability to maintain constant electrical performance and detection characteristics over a prolonged period of use. Prior art / State of the art restrictions

[0009] A first known solution for limiting dark currents in a radiation detector consists of mixing a 3D perovskite powder with another 2D perovskite powder to create an absorption structure with a mass heterojunction. The drawback of this solution is that limiting the dark current comes at the expense of detector sensitivity, which drastically limits the possibility of improving the signal-to-noise ratio.

[0010] A second known solution for limiting dark currents in a radiation detector consists of alternating 3D perovskite layers with 2D perovskite layers to create an absorption structure. The drawback of this solution is that the detection current is limited. Furthermore, the process for manufacturing a layer entirely of 2D perovskite is very complicated. Addressing the problem and proposing a solution

[0011] To overcome the limitations of existing solutions, the invention proposes a powdered or sintered composition comprising particles having a core-shell structure with a 3D perovskite core and a 2D perovskite coating. The composition according to the invention is intended to provide an absorption structure for a low-dark-current radiation detection device. The microstructure of the particle according to the invention makes it possible to significantly reduce the dark current while simultaneously improving sensitivity, which is not possible with prior art solutions.

[0012] The detection devices comprising the composition according to the invention also exhibit better stability of electrical behavior over time compared to state-of-the-art solutions.

[0013] Furthermore, according to a particular aspect of the invention, the composition comprises particles having an external coating which includes reticular chemical groups enabling the improvement of the mechanical robustness of an absorption structure obtained by compaction and chemical cohesion of said composition.

[0014] The invention further proposes a method for manufacturing the composition according to the invention based on liquid treatment rather than co-milling or alternating layer deposition. The liquid chemical treatment induces a crystalline phase change in the starting perovskite material after treatment at the external surface of the grains. Summary / Claims

[0015] The invention relates to a composition comprising a plurality of distinct particles in which at least one particle comprises: - a core made of a first material in three-dimensional perovskite with chemical formula ABX3; - a coating of a second material in two-dimensional perovskite of chemical formula RA'N iB'nX'3n+i or R2A'N.iB'NX'3N+i disposed on an external surface of the core; A and A' each being chosen from a first group of cations or an alloy of the elements of the first group of cations; B and B' each being chosen from a second group of inorganic cations or an alloy of the elements of the second group of inorganic cations; X and X' each being chosen from a group of halogens or an alloy of the elements of the halogen group; R being chosen from a third group of organic cations or an alloy of the elements of the third group of organic cations; N being a strictly positive natural number. The coating being formed by the stacking of a plurality of sheets, each sheet being formed by a stacking of N layers of B'X'6 octahedra; the sheets being separated from each other by a separating layer comprising the cation R.

[0016] According to a particular aspect of the invention, the first group of cations comprises cesium (Cs), rubidium (Rb), potassium (K), the organic compound CH3-NH3, the organic compound CH5-N2, and the organic compound CH6-N3. The second group of cations comprises lead (Pb), tin (Sn), germanium (Ge), silicon (Si), silver (Ag), bismuth (Bi), gold (Au), gallium (Ga), iron (Fe), and arsenic (As). The halogen group comprises bromine (Br), iodine (I), and chlorine (Cl).

[0017] According to a particular aspect of the invention, the third group of cations comprises a linear alkyl chain, a branched chain, a cyclic alkyl chain, an aromatic chain.

[0018] According to a particular aspect of the invention, each separation layer comprises a crosslinkable chemical group selected from the vinyl, epoxy, aldehyde, alcohol, ester, urethane, imide, amine, acrylate, alkynes, polyyne groups.

[0019] According to a particular aspect of the invention, the thickness of the envelope is less than 500nm.

[0020] According to a particular aspect of the invention, the first three-dimensional perovskite material has a first energy gap. The second two-dimensional perovskite material has a second energy gap strictly greater than the first energy gap.

[0021] According to a particular aspect of the invention, the first three-dimensional perovskite material has a first valence band maximum value. The second two-dimensional perovskite material has a second valence band maximum value that is strictly greater than the first valence band maximum value.

[0022] According to a particular aspect of the invention, the cations A and A' are identical, the cations B and B' are identical and the halogens X and X' are identical.

[0023] The invention also relates to a radiation absorption structure comprising a pellet made up of the composition according to the invention.

[0024] The invention also relates to a radiation detection device comprising: an absorption structure according to the invention; a first electrode made of an electrically conductive material disposed on a first face of the absorption structure and a second electrode made of an electrically conductive material disposed on a second face of the absorption structure opposite said first face.

[0025] The invention also relates to a first method for manufacturing a composition according to the invention comprising the following steps: - (i) Immerse, with mixing, a starting composition comprising particles in a first three-dimensional perovskite material of formula ABX3 in a solution comprising an organic ammonium halide salt of formula R-NH3X' or X'H3N-R-NH3X' dissolved in a solvent having a dipole moment less than 3; X and X' each being selected from a group of halogens or an alloy of elements from the halogen group; - (ii) filter the solution obtained under vacuum to recover the immersed composition; - (iii) immerse, with stirring, the composition recovered by filtration in a rinsing liquid insoluble in water and miscible with the solvent while maintaining the filtration under vacuum; - (iv) recover the composition treated by the rinsing liquid and thermally treat it at a temperature greater than or equal to 100°C for a predetermined time.

[0026] According to a particular aspect of the invention, the solution of step (i) further comprises a salt of formula A'X' and / or a salt of formula B'X'; A' being a cation distinct from A and being chosen from the first group of cations; B' being a cation distinct from B and being chosen from the second group of inorganic cations.

[0027] According to a particular aspect of the invention, the solvent is an alcohol or an ethyl acetate or a methyl acetate.

[0028] According to a particular aspect of the invention, the organic ammonium halide salt comprises a linear alkyl chain, or a branched alkyl chain, or a cyclic alkyl chain, or an aromatic chain having at least one crosslinkable chemical group selected from the vinyl, epoxy, aldehyde, alcohol, ester, urethane, imide, amine, acrylate groups.

[0029] According to a particular aspect of the invention, the rinsing liquid is Toluene or heptane or hexane or o-Xylene.

[0030] According to a particular aspect of the invention, the concentration of organic ammonium halide salt in the solution is between 2 mg / mL and 100 mg / mL.

[0031] The invention also relates to a second method of manufacturing a radiation absorption structure comprising the following steps: (i') providing a composition obtained by the first manufacturing method according to the invention in powder form or in sintered form; (ii') hot press said composition placed in a mold until a solid structure is obtained. Detailed description

[0032] Other features and advantages of the present invention will become more apparent from the following description in relation to the following accompanying drawings.

[0033] [Fig-1] illustrates a zoomed view of the perovskite composition according to the invention.

[0034] [Fig.2a] illustrates the crystalline phase of the core of a particle of the composition in perovskites according to the invention.

[0035] [Fig.2b] illustrates the crystalline phase of the coating of a particle of the perovskite composition according to the invention.

[0036] [Fig.3] illustrates a band diagram of the perovskite composition according to the invention.

[0037] [Fig.4] illustrates a cross-sectional view of a radiation detector according to the invention.

[0038] [Fig. 5a] illustrates sensitivity measurements as a function of the dark current of the radiation detector according to the invention compared with a detector according to the state of the art.

[0039] [Fig. 5b] illustrates the dark current over time of the detector radiation according to the invention in comparison with a detector according to the state of the art.

[0040] [Fig.6] illustrates a method for manufacturing a composition according to a first method of the realization of the invention.

[0041] [Fig.7] illustrates a method for manufacturing an absorption structure of radiation according to the invention.

[0042] [Fig.8] illustrates a method for manufacturing a radiation detection device DI of radiation according to the invention.

[0043] Figure 1 illustrates a zoomed view of the perovskite composition Cl according to the invention. The Cl composition is in powder or sintered form comprising a plurality of particles (also called grains) distinct from one another. The Cl composition comprises a first group of three-dimensional (3D) perovskite PI particles of formula ABX3 and a second group of P2 particles having a core-shell structure according to the invention. Advantageously, the C2 composition comprises only P2 particles having a core-shell structure according to the invention. Each P2 particle of the second group comprises a core 11 of a first three-dimensional (3D) perovskite of formula ABX3 and a coating 12 of a second two-dimensional (2D) perovskite of formula RA'n_iB'nX'3n+i or R2A'n_iB'nX'3n+i. A and A' are each chosen from a first group of cations or an alloy of elements from the first group of cations.B and B' are each chosen from a second group of inorganic cations or an alloy of elements from the second group of inorganic cations. X and X' are each chosen from a group of halogens or an alloy of elements from the halogen group. R is chosen from a third group of organic cations or an alloy of elements from the third group of organic cations.

[0044] By way of example, cations A and A' are each selected from cesium Cs, rubidium Rb, potassium K, the organic compound CH3-NH3, the organic compound CH5-N2, the organic compound CH6-N3, or an alloy of said elements. Cations B and B' are each selected from lead Pb, tin Sn, germanium Ge, silicon Si, or an alloy of said elements. Halogens X and X' are each selected from bromine Br, iodine I, chlorine Cl, or an alloy of said elements.

[0045] By way of example, the cation R is chosen from a linear alkyl chain, a cyclic alkyl chain (such as butyl, hexyl, octyl or cyclohexyl) or a simple or poly-aromatic aromatic chain (such as phenylethyl, polythiophenyl, naphthyl or anthracyl) or a mono- or poly-fluorinated, brominated or more generally halogenated aromatic chain (typically 3F-PEA, 4F-PEA, 5F-PEA, 5Br-PEA) or a mixture of the aforementioned chains and halides.

[0046] The coating 12 is disposed on at least a portion of the outer surface of the core 11. On the one hand, the coating 12 blocks dark currents and improves electrical stability over time when using the Cl composition to form an absorption structure for a radiation detector. On the other hand, the 3D perovskite core generates a sufficient photoconversion current to ensure good detector sensitivity. The combination of a 3D perovskite core 11 with a 2D perovskite coating 12 makes it possible to block dark currents without blocking the current of photocharges generated following exposure to radiation.

[0047] Advantageously, the coating 12 is disposed over the entire outer surface of the core 11 so as to form an envelope covering the entire core 11. This allows for better blocking of dark currents through an absorption structure formed by the CL composition

[0048] Advantageously, the thickness of the coating 12 is less than 500 nm to obtain optimal performance between: on the one hand, the reduction of dark currents and on the other hand, the intensity of the generated photocurrent and thus the detection sensitivity.

[0049] According to a particular aspect of the invention, the elements A', B', and X' constituting the perovskite of the coating 12 are respectively identical to the elements A, B, and X constituting the perovskite of the core 11. In this case, each particle P2 is a mass heterojunction generated by a change in crystalline phase and morphology (a 2D phase) at the surface of the perovskite grain (a 3D phase). The coating 12 corresponds to a surface phase change within the grain itself, and not to an external layer obtained by deposition. This embodiment has the advantage of allowing each grain to be functionalized individually via a chemical reaction, since the surface treatment of a particle remains difficult to control using layer deposition techniques.

[0050] Advantageously, the characteristic dimension of the PI and P2 particles of the Cl composition is between 100 nm and 100 pm. The characteristic dimension is understood to be the longest dimension that characterizes the shape of the grain, for example, the diameter for a spherical or quasi-spherical grain and the length for a grain in a sintered assembly. This makes it possible to limit the possibility of ion migration within a volume formed by the Cl composition and thus block the dark current associated with ion movement.

[0051] A radiation absorption structure according to the invention comprises at least one layer formed by the compressed Cl composition such that each particle P2 presents a contact zone with at least one adjacent particle so as not to degrade the conduction of the photocurrent corresponding to the fluxes of photogenerated charge carriers following the exposure of the absorption structure to incident radiation.

[0052] Figure 2a illustrates the three-dimensional 3D crystalline phase of the core 11 of a P2 particle of composition Cl in ABX3 perovskites according to the invention. The core 11 exhibits a phase in a 3D perovskite crystal lattice formed by a plurality of octahedra arranged periodically. Each cation B is surrounded by six anions X, forming a BX6 octahedron, which constitutes the basic building block of this structure. The BX6 octahedra share their vertices with other adjacent octahedra. Thus, in a unit cell of the perovskite structure, each octahedral vertex is occupied by an anion X, each anion X being shared between two adjacent octahedra. Furthermore, each cation A is located in the space bounded by eight adjacent octahedra. This arrangement creates a continuous and periodic three-dimensional lattice characteristic of 3D perovskite.

[0053] Figure 2b illustrates the 2D crystalline phase of the coating 12 of a particle P2 of composition Cl in perovskite RA'n_iB'nX'3n+i or R2A'n_iB'nX'3n+i according to the invention. The crystal lattice of said 2D perovskite is formed by a plurality of octahedra B'X'6 arranged in periodic sheets 121, 123, 125. The sheets are separated from each other by a separating layer 122, 124 comprising the cation R. Each sheet 121, 123, 125 is composed of N layers formed of several adjacent octahedra, N being a natural number greater than or equal to 1. Octahedra belonging to the same layer share their vertices within said layer. This arrangement forms a two-dimensional periodic network characteristic of 2D perovskites, where the interactions between the sheets are mainly ensured by the intercalated cations R.The crystalline phase 201 illustrates the coating 12 with N=1, which corresponds to a sheet 121 formed by a single layer of interconnected B'X'6 octahedra. The crystalline phase 202 illustrates the coating 12 with N=2, which corresponds to a sheet 121 formed by the stacking of two layers of interconnected B'X'6 octahedra. The smaller N is, the more the coating blocks dark currents. In the context of the invention, the number of layers per sheet in the coating 12 is between 1 and 5.

[0054] To explain the mechanism of dark current blocking by the Cl composition according to the invention, [Fig. 3] illustrates a band diagram of the perovskite composition according to the invention. To simplify the explanation, [Fig. 3] is limited to the energy band diagram obtained by two adjacent P2 particles. in an absorption structure of a radiation detector. The two particles are confined between the two electrodes ELI and EL2 of the radiation detector.

[0055] The 3D perovskite forming the core 11 is a semiconductor having a first energy gap Egl, a first minimum conduction band value Ecl, and a first maximum valence band value Evl. The 2D perovskite forming the coating 12 is a semiconductor having a second energy gap Eg2 > Egl, a second minimum conduction band value Ec2 > Ecl, and a second maximum valence band value Ev2 > Evl.

[0056] The inequality Eg2 > Egl allows for the creation of an energy barrier at the transition from a particle P2 to an adjacent particle, thereby blocking the migration of C+ and A- ions from one particle to the other. The A- and C+ ions thus remain trapped in the core 11 of the particle P2. This significantly reduces the dark current associated with the migration of ions from one particle to another. Furthermore, the energy barrier blocks the migration of ions from the ELI and EL2 electrodes to the interface with the absorption structure and prevents them from penetrating the absorption structure. This provides an additional advantage: improved electrical stability of a radiation detection device with an absorption structure made using the CL II composition. As a result, the coating 12 of the P2 particles allows for the passivation of the absorption structure with respect to the ELI and EL2 electrodes.This makes it possible to fabricate electrodes with materials such as gold, silver, or platinum, which were incompatible with known structures due to migration problems during use. The inequality Ev2 > Evl ensures good transfer of photogenerated charge carriers (in this case, holes) from one particle to another, up to the collection electrode, to obtain a photocurrent following irradiation.

[0057] Figure 4 illustrates a cross-sectional view of a DI radiation detection device according to the invention. The DI detection device is formed by a stack of layers arranged in a Z-direction. The layer stack comprises an absorption structure SPD, an upper electrode ELI, and a lower electrode EL2. The absorption layer CA is designed to convert an incident ray into positive and negative electrical charges. The upper electrode ELI, made of a conductive material, is designed to collect electrical charges of a predetermined sign, in this case, holes. The lower electrode EL2, also made of a conductive material, is designed to collect electrical charges of the opposite sign, in this case, electrons. The absorption structure SPD is arranged between the upper electrode ELI and the lower electrode EL2.

[0058] The SPD absorption structure is formed by a solid pellet-shaped layer obtained by compressing the composition Cl initially in the form powdered. Each of the PI,P2 particles of the Cl composition has a contact interface with at least one other adjacent particle of the compressed Cl composition. For a DI detection device for X-rays or gamma rays, the thickness of the CsPbBr3 CA absorption layer is between 100 nm and 5000 pm. More specifically, when the DI detection device is intended for mammography, the average value of the absorbed energy spectrum is 20 keV. Thus, the SPD absorption structure has a thickness between 50 pm and 300 pm, preferably 200 pm. Alternatively, when the DI detection device is intended for medical radiology with an average value of the absorbed energy spectrum of 50 keV, the SPD absorption structure has a thickness between 300 pm and 1500 pm, preferably 1000 pm.Alternatively, when the DI detection device is intended for medical radiology with a central value of the absorbed energy spectrum of 90keV, the SPD absorption structure has a thickness between 800pm and 2500pm, preferably equal to 2000pm.

[0059] Advantageously, the SPD absorption structure is formed by a layer consisting of the composition Cl according to the invention, wherein the cation R of the separation layer 122,124 between the sheets comprises one or more crosslinkable chemical groups selected, for example, from vinyl, epoxy, aldehyde, alcohol, ester, urethane, imide, amine, acrylate, alkyne, or polyyne groups. Within the separation layer 122,124, the crosslinkable chemical groups react to thermal, light, or chemical stimulation by forming covalent chemical bonds with each other. Thus, in addition to its primary function of passivating the surface of the perovskite grains, the R group has an additional function of improving the mechanical strength of the compacted layers. During compaction, the R groups of the different grains create chemical bridges between them (crosslink), ensuring strong mechanical cohesion between the grains.More advantageously, the crosslinkable chemical group is a thermo-crosslinkable polymer such as alkynes or polyynes, which is crosslinked during a drying step in the manufacturing of the component. This makes it possible to obtain mechanical cohesion without the need for an additional step in the manufacture of the composition according to the invention.

[0060] For example, the allylamine molecule of the type CH2=CH-CH2-NH2 can passivate the surface of MAPbR perovskite grains during the chemical treatment of the powder, forming a 2D perovskite layer around these grains with the allyl groups oriented towards the outside of the grain (at the extreme surface). Under the effect of compaction and heat treatment, the vinyl groups react with each other to form covalent chemical bridges between the grains, thus improving the mechanical strength of the layer.

[0061] The lower electrode EL2 is made of an electrically conductive material. By way of example, the lower electrode EL2 is made of a metal such as gold, silver, chromium and platinum; or of a conductive oxide such as indium tin oxide (ITO) and fluorine-doped tin dioxide (FTO); or of a conductive organic material such as carbon and carbon-60. By way of example, the lower electrode EL2 has a thickness of between 50 nm and 500 nm, preferably 200 nm.

[0062] The upper electrode ELI is made of an electrically conductive metallic material with a thickness between 50 nm and 500 nm (preferably 200 nm). For example, the upper electrode ELI is made of a metal such as gold, silver, chromium, and platinum; or of a conductive oxide such as indium tin oxide (ITO) and fluorine-doped tin dioxide (FTO); or of a conductive organic material such as carbon and carbon-60. Other types of conductive layers can also be used. These alternatives include metals, conductive polymers, carbon-based inks, carbon nanotubes, and metallic nanowires. Recall that an electrical voltage VDD is applied between the upper electrode ELI and the lower electrode EL2 to collect the charges generated at both electrodes.

[0063] Figure 5a illustrates the results of sensitivity measurements as a function of the dark current of the DI radiation detector according to the invention compared with a detector according to the prior art. The sensitivity derived from the photocurrent Jph evaluates the detection efficiency of the device, while the dark current partially evaluates the noise in the device. The triangular points correspond to measurements obtained with several samples based on a Cl composition according to the invention. The circular points correspond to measurements obtained with several absorption structures based on a C0 composition formed by uncoated 3D perovskite grains according to the prior art.

[0064] The dark current measurements for composition Cl according to the invention are between 1.5 nA mm2 and 5 nA mm2, whereas the dark current measurements for composition C0 according to the prior art are between 13 nA mm2 and 14 nA mm2. The invention thus makes it possible to reduce the dark current by up to 90% compared to the prior art.

[0065] The sensitivity measurements for composition Cl according to the invention are between 2.5 pC.mGy'.cm2 and 4.25 pC.mGy'.cm2, whereas the dark current measurements for composition C0 according to the prior art are between 1.5 pC.mGy'.cm2 and 2.5 pC.mGy'.cm2. The invention thus makes it possible to improve the sensitivity by 50% to 100% compared to the prior art.

[0066] Figure 5b illustrates the dark current over time of the radiation detector according to the invention (solid line) compared with a detector according to the prior art (dashed line). The average dark current in a DI device according to the invention is less than 100 nA. The average dark current in a device according to the prior art (uncoated 3D perovskite grains) is greater than 500 nA.

[0067] Figure 6 illustrates a manufacturing process PROC1 for a composition Cl according to a first embodiment of the invention. The first step (i) consists of immersing a starting composition C0 comprising particles of a first three-dimensional 3D perovskite of formula ABX3 in a solution comprising an organic ammonium halide salt of formula R-NH3X or XH3N-R-NH3X dissolved in a solvent. The starting composition C0 is in powder form or sintered with 3D perovskite particles with: - Selected from cesium Cs, rubidium Rb, potassium K, the organic compound CH3-NH3, the organic compound CH5-N2, the organic compound CH6-N3 or an alloy of said elements; - B chosen from lead Pb, tin Sn, germanium Ge, silicon Si, silver Ag, bismuth Bi, gold Au, gallium Ga, iron Fe, arsenic As or an alloy of said elements; - X chosen from bromine Br, iodine I, chlorine Cl or an alloy of said elements. The organic ammonium halide salt of formula R-NH3X' or X'H3N-R-NH3X' comprises an R group selected from a linear alkyl chain, a cyclic alkyl chain (such as butyl, hexyl, octyl or cyclohexyl), a branched alkyl chain or a simple or poly-aromatic aromatic chain (such as phenylethyl, polythiophenyl, naphthyl or anthracyl) or a mono- or poly-fluorinated, brominated or more generally halogenated aromatic chain (typically 3F-PEA, 4F-PEA, 5F-PEA, 5Br-PEA) or a mixture of the aforementioned chains and halides. Advantageously, the organic ammonium halide salt comprises one or more crosslinkable chemical groups selected from vinyl, epoxy, aldehyde, alcohol, ester, urethane, imide, amine, acrylate, alkynes or polyynes.

[0068] Element X' is chosen from bromine (Br), iodine (I), chlorine (Cl), or an alloy of said elements. Advantageously, element X' may be identical to element X of the starting composition C0 (X=X'). The solvent acting as the reaction medium advantageously has a dipole moment of less than 3. The solvent may be an alcohol, ethyl acetate, or methyl acetate.

[0069] The solution thus formed with the 3D perovskite powder in suspension is vigorously stirred by magnetic stirring or by motorized blades for a predetermined duration greater than 1 min. During the first step (i) a self-assembly chemical reaction occurs between the organic ammonium halide salt and the 3D perovskite grains. This induces a change in the morphology at the outer surface of the grains of the initial composition so as to obtain a group of particles of the immersed composition having a core-shell structure according to the invention.

[0070] The concentration of the organic ammonium halide salt is between 2 mg / mL and 100 mg / mL to obtain coatings that adhere to the grains while remaining thin enough not to degrade the detection current.

[0071] By way of non-limiting example, the starting composition C0 is a MAPbI3 perovskite powder with a solution containing a long amine halide (phenylethylammonium iodide, PEAI) dissolved at the desired concentration in anhydrous isopropanol (IPA).

[0072] To manufacture a composition Cl according to the invention in which the cation A' of the second two-dimensional perovskite material is different from the cation A, the solution of step (i) of the process PROC1 further comprises a salt of formula A'X' with A' selected from cesium Cs, rubidium Rb, potassium K, the organic compound CH3-NH3, the organic compound CH5-N2, the organic compound CH6-N3 or an alloy of said elements.

[0073] To manufacture a composition Cl according to the invention in which the cation B' of the second two-dimensional perovskite material is different from the cation B, the solution of step (i) of the process PROC1 further comprises a salt of formula B'X' with B' selected from lead Pb, tin Sn, germanium Ge, silicon Si, silver Ag, bismuth Bi, gold Au, gallium Ga, iron Fe, arsenic As or an alloy of said elements.

[0074] The second step (ii) consists of filtering the resulting solution under vacuum to recover the immersed composition. For example, the filtration is carried out through a polytetrafluoroethene (PTFE) filter with a pore size of 0.45 pm.

[0075] Optionally, when all of the solution has been evacuated, a first copious rinse is carried out with a rinsing liquid insoluble in water and miscible with the solvent while maintaining the filtration under vacuum.

[0076] The third step (iii) consists of immersing the composition recovered by filtration, with stirring, in a rinsing liquid that is insoluble in water and miscible with the solvent, while maintaining vacuum filtration. The rinsing liquid may be toluene, heptane, hexane, or o-xylene. Immersion is maintained for a period of 5 minutes or more, with stirring to remove any remaining residue from the treatment solution.

[0077] Optionally, a second filtering step similar to the second step (ii) is carried out with abundant rinsing with the rinsing liquid.

[0078] The fourth step (iv) consists of recovering the rinsed composition and heat-treating it at a temperature of 100°C or higher for a predetermined time to remove moisture and solvent residues that impair the functioning of the absorption structure made from the composition obtained. In the embodiment where the organic ammonium halide salt comprises one or more heat-crosslinkable chemical groups, this step also crosslinks said groups, thereby improving the mechanical cohesion between the grains.

[0079] Advantageously, the steps of the PROC1 process are carried out in a dry environment (relative humidity < 5%), ideally in a glove box. Otherwise, the humidity of the air, and to a lesser extent the presence of oxygen, can partially alter the Cl composition obtained.

[0080] Figure 7 illustrates a manufacturing process PROC2 for a radiation SPD absorption structure according to the invention. The first step (i') consists of providing a composition Cl in powder or sintered form obtained by the manufacturing process PROC1. Alternatively, the first step (i') consists of carrying out the steps of the process PROC1.

[0081] The second step (ii') consists of hot-pressing the composition placed in a mold until a solid structure, for example in the form of a pellet, is obtained. For example, a mass of powder corresponding to the desired pellet thickness is weighed and poured into a mold placed in a sealed, argon-controlled environment compartment (of the glove box type). The assembly is then placed in a hot press at 70°C under a pressure of 2000 kg for 30 minutes, for example. The mold is then cooled before the pellet is removed.

[0082] Figure 8 illustrates a manufacturing process PROC3 for a radiation detection device (DI) according to the invention. The first step (i”) consists of providing an SPD absorption structure obtained by the manufacturing process PROC2. Alternatively, the first step (i”) consists of carrying out the steps of the PROC2 process.

[0083] The second step (ii”) consists of depositing the upper ELI electrode onto a first face of the SPD absorption structure. The upper ELI electrode is generally a metallic layer with a thickness ranging from 1 µm to 1 µm. This material can be chromium, copper, gold, platinum, tungsten, titanium, silver, bismuth, or indium. Vacuum deposition techniques, such as evaporation or sputtering, are preferred for its deposition. However, it is also possible to use other types of conductive layers and other thicknesses. These alternatives include metals, conductive polymers, carbon-based inks, carbon nanotubes, and metal nanowires. These layers can be deposited either by similar vacuum techniques or by printing techniques such as spraying, coating, spin-coating, or slot-die deposition.

[0084] The third step (üi”) consists of depositing the lower electrode EL2 on a second face of the SPD absorption structure opposite the first face. This step can be carried out in a similar manner to the second step (ii”).

Claims

Demands

1. Composition (Cl) comprising a plurality of distinct particles (PI, P2) in which at least one particle (P2) comprises: - a core (11) in a first three-dimensional (3D) perovskite material of chemical formula ABX3; - a coating (12) of a second material in two-dimensional (2D) perovskite of chemical formula RA'N iB'nX'3n+i or R2A'n_iB'nX'3n+i disposed on an outer surface (110) of the core (11); A and A' each being chosen from a first group of cations or an alloy of the elements of the first group of cations; B and B' each being chosen from a second group of inorganic cations or an alloy of elements from the second group of inorganic cations; X and X' each being chosen from a group of halogens or an alloy of elements from the halogen group; R being chosen from a third group of organic cations or an alloy of elements from the third group of organic cations; N being a strictly positive natural number; the coating (12) being formed by the stacking of a plurality of sheets (121,123,125), each sheet (121,123,125) being formed by a stacking of N layers of B'X'6 octahedra; the sheets being separated from each other by a separation layer (122,124) comprising the R cation.

2. Composition (Cl) according to claim 1 in which - the first group of cations consists of the following elements: cesium (Cs), rubidium (Rb), potassium (K), the organic compound CH3-NH3, the organic compound CH5-N2 and the organic compound CH6-N3; - and in which the second group of cations consists of the following elements: lead (Pb), tin (Sn), germanium (Ge), silicon (Si), silver (Ag), bismuth (Bi), gold (Au), gallium (Ga), iron (Fe), arsenic (As); - and in which the halogen group consists of the following elements: bromine (Br), iodine (I), chlorine (Cl).

3. Composition (Cl) according to any one of claims 1 or 2 wherein the third group of cations consists of the following: a linear alkyl chain, a branched chain, a cyclic alkyl chain, an aromatic chain.

4. Composition (Cl) according to any one of claims 1 to 3 wherein each separating layer (122,124) comprises a crosslinkable chemical group selected from the vinyl, epoxy, aldehyde, alcohol, ester, urethane, imide, amine, acrylate, alkynes, polyynes groups.

5. Composition (Cl) according to any one of claims 1 to 4 wherein the thickness of the coating (12) is less than 500nm.

6. Composition (Cl) according to any one of claims 1 to 5 wherein: - the first three-dimensional (3D) perovskite material has a first energy gap (Egl); - and the second two-dimensional (2D) perovskite material has a second energy gap (Eg2) strictly greater than the first energy gap (Egl).

7. Composition (Cl) according to any one of claims 1 to 6 wherein: - the first three-dimensional (3D) perovskite material has a first valence band maximum (Evl) value; - and the second two-dimensional (2D) perovskite material has a second valence band maximum (Ev2) value strictly greater than the first valence band maximum (Evl) value.

8. Composition (Cl) according to any one of claims 1 to 7 wherein the cations A and A' are identical, the cations B and B' are identical and the halogens X and X' are identical.

9. Radiation absorption structure (SPD) comprising a pellet made of the composition (Cl) according to any one of claims 1 to 8.

10. Radiation detection device comprising:

11.

12.

13. - an absorption structure (SPD) according to claim 9; - a first electrode (ELI) made of an electrically conductive material arranged on a first face of the absorption structure (SPD); - a second electrode (EL2) made of an electrically conductive material disposed on a second face of the absorption structure (SPD) opposite said first face. A manufacturing process (PR0C1) for a composition (Cl) according to claim 1 comprising the following steps: (i) Immerse, with stirring, a starting composition (CO) comprising particles in a first three-dimensional (3D) perovskite material of formula ABX3 in a solution comprising an organic ammonium halide salt of formula R-NH3X' or X'H3N-R-NH3X' dissolved in a solvent having a dipole moment less than 3; X and X' each being selected from a group of halogens or an alloy of elements from the halogen group; (ii) filter the solution obtained under vacuum to recover the immersed composition; (iii) immerse, with stirring, the composition recovered by filtration in a rinsing liquid insoluble in water and miscible with the solvent while maintaining the filtration under vacuum; (iv) recover the composition treated by the rinsing liquid and heat treat it at a temperature greater than or equal to 100°C for a predetermined time. Manufacturing process (PROC1) according to claim 11 wherein the solution of step (i) further comprises a salt of formula A'X' and / or a salt of formula B'X'; A' being a cation distinct from A and being chosen from the first group of cations; B' being a cation distinct from B and being chosen from the second group of inorganic cations. Manufacturing process (PROC1) according to any one of claims 11 or 12 wherein the solvent is an alcohol or an ethyl acetate or a methyl acetate.

14. A manufacturing process (PROC1) according to any one of claims 11 to 13 wherein the organic ammonium halide salt comprises a linear alkyl chain, or a branched alkyl chain, or a cyclic alkyl chain, or an aromatic chain having at least one crosslinkable chemical group selected from the vinyl, epoxy, aldehyde, alcohol, ester, urethane, imide, amine, acrylate groups.

15. A manufacturing process (PROC1) according to any one of claims 11 to 14 wherein the rinsing liquid is Toluene or Heptane or Hexane or o-Xylene.

16. A manufacturing process (PROC1) according to any one of claims 11 to 15 wherein the concentration of organic ammonium halide salt in the solution is between 2 mg / mL and 100 mg / mL.

17. A manufacturing process (PROC2) for a radiation absorption structure (SPD) comprising the following steps: (i') providing a composition (Cl) obtained by the manufacturing process according to any one of claims 11 to 16 in powder form or in sintered form; (ii') hot-pressing said composition placed in a mold until a solid structure is obtained.

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