Indirect flat panel detector and preparation method thereof

Abstract

The present invention provides an indirect flat-panel detector and a preparation method thereof, comprising: a substrate; a lower electrode layer; an organic light conversion layer, wherein the raw materials for the preparation thereof include a P-type organic photoelectric material, an N-type organic photoelectric material and an organic solvent for dissolving the P-type organic photoelectric material and the N-type organic photoelectric material; an upper electrode layer; a packaging layer, wherein the first packaging layer and the second packaging layer are alternately stacked in at least two groups, wherein the material of the first packaging layer includes parylene or polyimide, and the material of the second packaging layer includes aluminum oxide, silicon dioxide or silicon nitride; and a scintillator layer, wherein the material includes Ca 1‑x Sr x I2 or Ca 1‑x Sr x I2:yEu 2+ , where 0≤x≤1, 0.01%≤y≤5%. Using an organic light conversion layer and combining Ca 1‑x Sr x I2 or Ca 1‑x Sr x I2:yEu 2+ The scintillator layer of the material effectively improves the light response of the indirect flat-panel detector, greatly improves the sensitivity of the flat-panel detector, and enables the flat-panel detector to be used in low-dose application scenarios; in addition, by setting the encapsulation layer, damage to the organic light conversion layer when forming the scintillator layer can be effectively prevented.

Description

Technical Field

[0001] The invention belongs to the technical field of ray detection, and in particular relates to an indirect flat-panel detector and a preparation method thereof. Background Art

[0002] X-ray flat panel detectors (hereinafter referred to as flat panel detectors) are imaging devices that are sensitive to X-rays. They can be used in medical imaging (breast and chest examinations, radiotherapy, etc.), industrial non-destructive testing, security inspections and protection, etc. The size can reach tens of centimeters, and the pixel substrate can be composed of millions or even tens of millions of pixel unit circuits. Each pixel unit is usually composed of devices such as thin-film transistors (TFT) and photodiodes (PD).

[0003] Existing X-ray indirect flat-panel detectors use amorphous Si (a-Si) as the photosensitive material and CsI:Tl (thallium-doped cesium iodide) or Gd2O2S:Tb (terbium-doped gadolinium oxysulfide, referred to as GOS) as the X-ray conversion material (i.e., scintillator). The main reason for using this combination is that the peak of the response curve of amorphous Si is around 550nm, which is a good match with the luminescence of CsI or GOS. However, there are some problems with this combination: First, the external quantum efficiency (EQE) of the amorphous Si photodiode array has reached about 80%@550nm, and there is little room for significant improvement; In addition, the scintillator uses CsI:Tl or Gd2O2S:Tb single crystal solution, and its light yield is about 50,000 photons / MeV. Considering that in flat-panel detectors, the above two scintillators exist in the form of powder crystals or polycrystalline, and the defect density is higher than that of single crystals, resulting in a lower light yield than single crystals, about 35,000 photons / MeV. It is also difficult to significantly increase the light yield of existing scintillators by adjusting the chemical composition and process. Therefore, there is little room for significantly improving the detection efficiency (also called sensitivity) of flat-panel detectors under the existing a-Si+CsI or Gd2O2S combination, which limits its application in low-dose scenarios.

[0004] In recent years, the research on organic photodiodes (OPDs) has made great progress. The processing method of OPDs is simple, using a solution coating process, without the need for pixelation, and the entire process can be completed in an atmospheric environment without the need for high vacuum and plasma equipment, simplifying the process and reducing costs. In addition, Fig.11As shown, the response spectrum of OPD is much wider than that of amorphous Si, which provides a large choice space for the selection of scintillator materials to replace GOS or CsI. The combination of OPD + other scintillators can further subdivide the application of X-ray flat-panel detectors and form differentiated competition. For example, the use of this combination of OPD + other scintillators can make the detector more sensitive and suitable for some low-dose applications. Summary of the invention

[0005] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide an indirect flat-panel detector and a preparation method thereof, so as to solve the problem that the sensitivity of the prior art indirect X-ray flat-panel detector cannot be significantly improved, thereby limiting its low-dose application.

[0006] In order to achieve the above-mentioned object and other related objects, the present invention provides an indirect flat panel detector, the indirect flat panel detector comprising:

[0007] substrate;

[0008] A lower electrode layer is formed on the substrate;

[0009] An organic light conversion layer is formed on the lower electrode layer, and the raw materials for preparing the organic light conversion layer include a P-type organic photoelectric material, an N-type organic photoelectric material, and an organic solvent for dissolving the P-type organic photoelectric material and the N-type organic photoelectric material;

[0010] An upper electrode layer, formed on the organic light conversion layer;

[0011] A packaging layer formed on the upper electrode layer, wherein the packaging layer is formed by alternately stacking at least two groups of first packaging layers and second packaging layers, wherein the material of the first packaging layer includes parylene or polyimide, and the material of the second packaging layer includes aluminum oxide, silicon dioxide or silicon nitride;

[0012] A scintillator layer is formed on the encapsulation layer, wherein the material of the scintillator layer includes Ca 1-x Sr x I2 or Ca 1- x Sr x I2:yEu 2+ , where 0≤x≤1, 0.01%≤y≤5%.

[0013] Optionally, the encapsulation layer is formed by alternately stacking 3 to 5 groups of the first encapsulation layer and the second encapsulation layer, the thickness of the first encapsulation layer is between 500 nm and 1000 nm, and the thickness of the second encapsulation layer is between 10 nm and 50 nm.

[0014] Optionally, the flat-panel detector further includes a first interface layer and a second interface layer, the first interface layer is located on the upper surface of the organic light conversion layer, and the second interface layer is located on the lower surface of the organic light conversion layer; the material of the first interface layer includes at least one of Se, MoO3, WO3, NiO, V2O5 and PEDOT:PSS, and the material of the second interface layer includes at least one of TiO2, ZnO, AZO, MZO, SnO2 and PEIE; the thickness of the first interface layer is between 5nm and 100nm, and the thickness of the second interface layer is between 10nm and 100nm.

[0015] Optionally, the P-type organic photoelectric material includes at least one of P3HT and PCPDTBT; the N-type organic photoelectric material includes at least one of PC61BM and PC71BM; the organic solvent includes at least one of o-xylene, chloroform and tetralin; and the thickness of the organic light conversion layer is between 100nm and 2000nm.

[0016] Optionally, the material of the scintillator layer includes CaI2, CaI2:yEu 2+ 、SrI2、SrI2:yEu 2+ , Ca 0.9 Sr 0.1 I2 or Ca 0.9 Sr 0.1 I2:yEu 2+ .

[0017] The present invention also provides a method for preparing an indirect flat-panel detector, which can be used to prepare the above-mentioned indirect flat-panel detector. The preparation method comprises the following steps:

[0018] Providing a substrate, and preparing a lower electrode layer on the substrate;

[0019] Dissolving a P-type organic photoelectric material and an N-type organic photoelectric material in an organic solvent to prepare a light conversion material liquid, and preparing an organic light conversion layer on the lower electrode layer based on the light conversion material liquid;

[0020] Preparing an upper electrode layer on the organic light conversion layer;

[0021] Preparing a packaging layer on the upper electrode layer, wherein the packaging layer is formed by alternately stacking at least two groups of first packaging layers and second packaging layers, wherein the material of the first packaging layer includes parylene or polyimide, and the material of the second packaging layer includes aluminum oxide, silicon dioxide or silicon nitride;

[0022] A scintillator layer is prepared on the encapsulation layer, wherein the material of the scintillator layer includes Ca 1-x Sr x I2 or Ca1-x Sr x I2:yEu 2+ , where 0≤x≤1, 0.01%≤y≤5%.

[0023] Optionally, after forming the lower electrode layer, the step of forming a second interface layer is also included, and the second interface layer is formed on the lower surface of the organic light conversion layer; after forming the organic light conversion layer, the step of forming a first interface layer is also included, and the first interface layer is formed on the upper surface of the organic light conversion layer.

[0024] Optionally, the encapsulation layer is formed by alternately stacking 3 to 5 groups of the first encapsulation layer and the second encapsulation layer, the thickness of the first encapsulation layer is between 500 nm and 1000 nm, and the thickness of the second encapsulation layer is between 10 nm and 50 nm.

[0025] Optionally, the first encapsulation layer is formed by a CVD process; the second encapsulation layer of the aluminum oxide material is formed by an ALD process; and the second encapsulation layer of the silicon dioxide material or the silicon nitride material is formed by a PVD process.

[0026] Optionally, the scintillator layer is prepared by a thermal evaporation process, and the temperature of the thermal evaporation is between 600° C. and 800° C.

[0027] Optionally, when the scintillator layer is prepared by thermal evaporation, a reducing gas is introduced into the furnace, and the reducing gas includes at least one of H2, CH4 and NH3.

[0028] Optionally, the reducing gas is H2, and N2 is also introduced into the furnace, and the volume of H2 accounts for between 5% and 75% of the mixed gas.

[0029] Optionally, the flow rate of the reducing gas introduced into the furnace is between 10cc / min and 100cc / min.

[0030] Alternatively, Ca is prepared by thermal evaporation 1-x Sr x The main raw materials used in the scintillator layer of I2 include CaI2 and SrI2; CaI2 is prepared by evaporation 1-x Sr x I2:yEu 2+ The main materials used in the scintillator layer include CaI2, SrI2 and EuI2.

[0031] Optionally, the scintillator layer is prepared by thermal evaporation and further includes a compensation raw material, the compensation raw material is a single substance I2, and the mass ratio of the compensation raw material to the main raw material is between 0.1% and 0.5%.

[0032] As described above, the present invention provides an indirect flat-panel detector and a preparation method thereof, wherein an organic light conversion layer is used to replace the existing amorphous Si to realize photoelectric conversion. Since the response spectrum of the organic light conversion layer is very wide, the light response of the photosensitive layer of the flat-panel detector can be broadened to the blue light region, and the response in the blue light region is similar to that of 550nm yellow-green light. Based on this, the present invention further arranges a Ca 1-x Sr x I2 or Ca 1-x Sr x I2:yEu 2+ The scintillator layer of the material has a significantly improved light yield in the blue light region compared to the CsI:Tl scintillator material, thereby effectively improving the light response of the indirect flat-panel detector, greatly improving the sensitivity of the flat-panel detector, and enabling the flat-panel detector to be used in low-dose application scenarios; in addition, by providing the encapsulation layer, damage to the organic light conversion layer when forming the scintillator layer can be effectively prevented to ensure the sensitivity of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It shows a schematic diagram of the manufacturing process of the indirect flat panel detector of the present invention.

[0034] Figures 2 to 9 It is a schematic diagram showing the structure of each step of the indirect flat panel detector preparation process of the present invention, wherein: Fig. 9 Also shown is a schematic structural diagram of the indirect flat panel detector of the present invention.

[0035] Fig.10 It is a schematic diagram showing an equivalent circuit of the organic light conversion layer and the TFT layer of the indirect flat panel detector of the present invention.

[0036] Fig.11 Shown are the normalized response spectrum of the organic light conversion layer of the indirect flat panel detector of the present invention and the normalized emission spectrum of the CsI:Tl photosensitive material.

[0037] Component number description

[0038] 100 Base 101 Lower electrode layer 102 Organic light conversion layer 103 Upper electrode layer 104 Encapsulation layer 104a First packaging layer 104b Second packaging layer 105 Scintillator layer 106 First interface layer 107 Second interface layer 108 Transistor source 109 Transistor Drain 110 Photodiode 111 Readout line 112 Scan Line 113 Transistor Gate S1~S5 step DETAILED DESCRIPTION

[0039] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0040] For example, when describing the embodiments of the present invention in detail, for the sake of convenience, the cross-sectional view showing the device structure will not be partially enlarged according to the general scale, and the schematic view is only an example, which should not limit the scope of protection of the present invention. In addition, in actual production, the three-dimensional space dimensions of length, width and depth should be included.

[0041] For ease of description, spatially relative terms such as "under", "below", "below", "below", "above", "on", etc. may be used herein to describe the relationship of one element or feature shown in the drawings to other elements or features. It will be understood that these spatially relative terms are intended to encompass other orientations of the device in use or operation in addition to the orientation depicted in the drawings. In addition, when a layer is referred to as being "between" two layers, it can be the only layer between the two layers, or one or more intervening layers may also be present.

[0042] In the context of the present application, a structure in which a first feature is described as being "above" a second feature may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features are formed between the first and second features, such that the first and second features may not be in direct contact.

[0043] See also Figures 1 to 10 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the illustrations only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0044] like Fig. 9 See Figures 1 to 8 and Fig.10 This embodiment provides an indirect flat panel detector, the indirect flat panel detector comprising:

[0045] Base 100;

[0046] A lower electrode layer 101 is formed on the substrate 100;

[0047] An organic light conversion layer 102 is formed on the lower electrode layer 101, and the raw materials for preparing the organic light conversion layer 102 include a P-type organic photoelectric material, an N-type organic photoelectric material, and an organic solvent for dissolving the P-type organic photoelectric material and the N-type organic photoelectric material;

[0048] An upper electrode layer 103 is formed on the organic light conversion layer 102;

[0049] The encapsulation layer 104 is formed on the upper electrode layer 103. The encapsulation layer 104 is formed by alternately stacking at least two groups of first encapsulation layers 104a and second encapsulation layers 104b. The material of the first encapsulation layer 104a includes parylene or polyimide, and the material of the second encapsulation layer 104b includes aluminum oxide, silicon dioxide or silicon nitride.

[0050] The scintillator layer 105 is formed on the encapsulation layer 104. The material of the scintillator layer 105 includes Ca 1-x Sr x I2 or Ca 1-x Sr x I2:yEu 2+ , where 0≤x≤1, 0.01%≤y≤5%.

[0051] In this embodiment, an organic light conversion layer is used to replace the existing amorphous Si to achieve photoelectric conversion. Since the response spectrum of the organic light conversion layer is very wide (such as Fig.11 As shown in FIG. 1 ), the photosensitive layer of the flat panel detector can be extended to the blue light region, and the response of the flat panel detector in the blue light region is similar to that of 550nm yellow-green light. Based on this, the present embodiment further arranges Ca on the organic light conversion layer. 1- x Sr x I2 or Ca 1-x Sr x I2:yEu 2+ The scintillator layer 105 of the material, the material properties of the scintillator layer 105 in this embodiment and the properties of the CsI:Tl scintillator material are shown in Table 1. The light yield of the scintillator layer 105 in this embodiment in the blue light region is greatly improved compared with the CsI:Tl scintillator material, thereby effectively improving the light response of the indirect flat-panel detector, greatly improving the sensitivity of the flat-panel detector, and enabling the flat-panel detector to be used in low-dose application scenarios.

[0052] Table 1

[0053] Chemical formula Density(g / cc) Light output (photons / Mev) Relaxation time (ns) Emission main peak (nm) Melting point(℃) CsI:Tl 4.51 ~56000 980 530~560 632 <![CDATA[CaI2]]> 3.96 ~86000 550 410 779 <![CDATA[CaI2:Eu 2+ ]]> 3.96 ~98000 790 470 779 <![CDATA[SrI2:Eu 2+ ]]> 4.55 ~90000 ~1200 435 645 <![CDATA[Ca 1-x Mr. x I2:I 2+ ]]> 3.96~4.55 90000~98000 Adjustable from 435 to 470nm. The higher the Sr content, the closer the main peak is to 435nm. 645 to 779

[0054] As an example, the substrate 100 includes a substrate and a transistor function layer formed on the substrate, wherein the transistor function layer includes a transistor source, and the transistor source is electrically connected to the lower electrode layer 101. Specifically, in an example, a structure of a substrate 100 is provided, including a substrate and a transistor function layer. In this example, the substrate may be a glass substrate, and the transistor function layer may be a TFT (Thin Film Transistor) layer. In this example, the transistor source (source) (see Fig.10The transistor source 108 in the lower electrode layer 101 is electrically connected to the lower electrode layer 101, that is, the lower electrode layer 101 is electrically connected to the organic light conversion layer 102 for signal transmission. Of course, the transistor functional layer also includes a transistor gate and a transistor drain. In one example, the transistor functional layer, such as the transistor source layer and the transistor drain layer in the TFT layer, shares the same material layer with the lower electrode layer. Of course, the structure of each material layer of the transistor and the positional relationship of the organic light conversion layer 102 can also be arranged and designed according to actual needs.

[0055] The organic light conversion layer 102 is a photoelectric conversion device made of organic semiconductor materials, which can convert light signals (photons) into carriers (charge-hole pairs) for detecting light signals. A new type of flat-panel detector is prepared by using organic semiconductor materials to replace silicon-based photosensitive materials (such as amorphous silicon and single crystal silicon) in existing flat-panel detectors. Flat-panel detectors based on organic photoelectric materials have the characteristics of simple structure and process, strong process compatibility, low cost, high sensitivity, etc., and can be applied to medical radiation imaging, industrial flaw detection, security inspection and other fields. For organic photoelectric materials, the light response spectrum covers a wide range, especially in the ultraviolet-blue light band of 300nm to 450nm and the deep red light-near infrared band of 675nm to 750nm. The absorption is strong, which increases the absorption of photons emitted by the scintillator, thereby improving the quantum efficiency of the device; it can be dissolved in certain organic solvents, making it possible to process devices by solution method under standard atmospheric pressure environment, abandoning the high vacuum and plasma equipment of traditional semiconductor processes; and it is easy to form films on a large area. Increasing the absorption of the above short-wave and long-wave by the photodiode can increase the external quantum efficiency of the photodiode. Increasing the sensitivity and quantum detection efficiency DQE (Detector quantum efficiency) of the detector, the ratio of the input signal-to-noise ratio (dose) to the output signal-to-noise ratio (image clarity) in spatial frequency expansion, comprehensively reflects the performance of the detector in terms of dose utilization and spatial resolution, and also reflects that the radiation dose of patients can be reduced.

[0056] As an example, the material of the organic light conversion layer 102 is composed of a P-type organic photoelectric material (donor material) and an N-type organic photoelectric material (acceptor material). The P-type organic photoelectric material may include: P3HT (named: poly (3-hexylthiophene-2,5-diyl)), and: PCPDTBT (named: poly [2,6- (4,4-bis- (2-ethylhexyl) -4H-cyclopentadien [2,1-b; 3,4-b '] dithiophene) -alt-4,7 (2,1,3-benzothiadiazole)]) one or a combination of two or more; the N-type organic photoelectric material may include: PC61BM (named: [6,6] -phenyl C 61 butyric acid methyl ester), and PC71BM (named: [6,6] -phenyl C 71 butyric acid methyl ester) one or a combination of two or more. In addition, in an example, the organic solvent includes at least one of o-xylene, chloroform and tetralin. The thickness of the organic light conversion layer 102 is between 100 nm and 2000 nm, including endpoint values, for example, may be 300 nm, 500 nm, 700 nm, 1000 nm, 1300 nm, 1500 nm, 1700 nm, etc.

[0057] like Fig. 9As shown, as an example, the flat panel detector of this embodiment also includes a first interface layer 106 and a second interface layer 107, the first interface layer 106 is located on the upper surface of the organic light conversion layer 102, and the second interface layer 107 is located on the lower surface of the organic light conversion layer 102; the material of the first interface layer 106 includes at least one of Se, MoO3, WO3, NiO, V2O5 and PEDOT:PSS, and the material of the second interface layer 107 includes at least one of TiO2, ZnO, AZO, MZO, SnO2 and PEIE; the thickness of the first interface layer 106 is between 5nm and 100nm, and the thickness of the second interface layer 107 is between 10nm and 100nm, including end points. The first interface layer 106 can be used as a hole transport layer when the device is working, which can realize the transmission of carrier holes and block the transmission of electrons. The hole transport layer separates the carriers in the organic photosensitive material film layer (the organic light conversion layer) so that the carriers can reach the electrode, avoiding the recombination of the carriers in the film layer, improving the quantum efficiency, preventing the reverse injection of charges, reducing the dark current, and improving the device sensitivity and image contrast. The presence of the hole transport layer can also reduce the work function at the interface of the light conversion layer; the second interface layer 107 can be used as an electron transport layer when the device is working, which can realize the transmission of carrier electrons and block the transmission of holes. The electron transport layer separates the carriers in the organic photosensitive material film layer (the organic light conversion layer) so that the carriers can reach the electrode, avoiding the recombination of the carriers in the film layer, improving the quantum efficiency, preventing the reverse injection of charges, reducing the dark current, and improving the device sensitivity and image contrast. The presence of the electron transport layer can also reduce the work function at the interface of the light conversion layer.

[0058] like Figure 8 As shown, the encapsulation layer 104 is formed by alternately stacking 3 to 5 groups of the first encapsulation layers 104a and the second encapsulation layers 104b. Figure 8 As shown in the figure, the encapsulation layer 104 is formed by alternating stacking of 4 groups of the first encapsulation layer 104a and the second encapsulation layer 104b, the thickness of the first encapsulation layer is between 500nm and 1000nm, and the thickness of the second encapsulation layer is between 10nm and 50nm. The encapsulation layer 104 can effectively prevent the damage to the organic light conversion layer 102 when the scintillator layer 105 is formed, so the thickness of the encapsulation layer cannot be too thin, which will not effectively protect the organic light conversion layer 102, and too thick will block light and reduce the sensitivity of the detector, so arranging 3 to 5 groups of the first encapsulation layer 104a and the second encapsulation layer 104b to alternately stack to form the encapsulation layer 104 can effectively protect the organic light conversion layer 102 and minimize the side effect of blocking light.

[0059] As an example, the material of the scintillator layer can be selected from CaI2, CaI2:yEu 2+ 、SrI2、SrI2:yEu 2+ , Ca 0.9 Sr 0.1 I2 or Ca 0.9 Sr 0.1 I2:yEu 2+ .

[0060] The working process of the indirect flat panel detector of this embodiment can be seen in Fig.10 The upper electrode layer 103 of the device is connected to the negative pole of the DC power supply, and the lower electrode layer 101 is electrically connected to the positive pole of the power supply. The electric field strength can be set according to actual conditions, such as 1 to 10 V / um. When the device is not exposed to external X-rays, the electrons and holes are exhausted in the organic light conversion layer 102 (a photosensitive layer prepared based on organic photoelectric materials), and theoretically no current is generated. When the device is exposed to X-rays, this embodiment adopts an upper light transmission method, and the X-rays cooperate with the scintillator layer 105 to ionize the organic light conversion layer material to generate photogenerated carriers (electron-hole pairs). Under the action of the electric field, the holes drift toward the upper electrode layer, and the electrons drift toward the lower electrode layer. However, a small amount of electrons will drift toward the upper electrode, and a small amount of holes will drift toward the lower electrode. The lower electrode layer is connected to the TFT source, that is, the transistor source 108, see Fig.10 As shown, the electrons are transferred to the lower electrode layer and then to the TFT source, and are stored in the TFT source; when the TFT is turned on (when the transistor gate 113 voltage is greater than the TFT threshold voltage, the TFT is in the on state, and the transistor source 108 and the transistor drain 109 are turned on), the electrons are transferred from the transistor source 108 to the transistor drain 109 (drain), and then transferred to the "readout line 111" and read by the external circuit. In addition, the equivalent circuit diagram also includes a signal control scanning line 112, which controls each pixel ( Fig.10 The combination of a photodiode and a TFT transistor in a pixel is called a pixel) does the same operation, and the grayscale of the final image depends on the amount of charge in the corresponding pixel (for example: the more charge stored, the higher the grayscale value, and the brighter the corresponding pixel).

[0061] like Figures 1 to 9 As shown, this embodiment also provides a method for preparing an indirect flat panel detector, and the preparation method can prepare the above-mentioned indirect flat panel detector, and the preparation method comprises the following steps:

[0062] like Figure 1 and Figure 2 As shown, step S1 is first performed to provide a substrate 100 and prepare a lower electrode layer 101 on the substrate 100 .

[0063] As an example, the material of the lower electrode layer 101 includes but is not limited to ITO (indium tin oxide) or Ag, and can be formed by sputtering or evaporation.

[0064] like Figure 1 , Figure 3 and Figure 4 As shown, step S2 is then performed to dissolve the P-type organic photoelectric material and the N-type organic photoelectric material in an organic solvent to prepare a light conversion material liquid, and to prepare an organic light conversion layer 102 (such as Figure 3 as shown).

[0065] As an example, the organic photoelectric material is composed of a P-type material (donor material) and an N-type material (acceptor material). The P-type material may include one or a combination of two or more of P3HT (named as poly(3-hexylthiophene-2,5-diyl)) and PCPDTBT (named as poly[2,6-(4,4-bis-(2-ethylhexyl)-4H-cyclopentadien[2,1-b;3,4-b′]dithiophene)-alt-4,7(2,1,3-benzothiadiazole)]); the N-type material may include one or a combination of two or more of PC61BM (named as [6,6]-phenyl C 61 butyric acid methyl ester) and PC71BM (named as [6,6]-phenyl C 71 butyric acid methyl ester). In addition, in one example, the organic solvent includes at least one of o-xylene, chloroform and tetralin. The light conversion material liquid may be prepared by weighing a P-type organic photoelectric material and an N-type organic photoelectric material in a certain ratio, dissolving them in the organic solvent, and then heating and stirring them sufficiently.

[0066] As an example, this embodiment prepares the organic light conversion layer 102 based on organic photoelectric materials based on a solution method, and the light conversion material liquid is coated on the lower electrode layer 101 by a solution method to form the organic light conversion layer 102, wherein the solution method includes at least one of scraping, inkjet printing, screen printing and slot-die. Based on the above method, the organic light conversion layer 102 is coated on the lower electrode layer 101, and the film thickness is 100nm to 2000nm, which can be 500nm, 1000nm, 1500nm. After coating the above film layer, it can be placed in an oven at 80-120°C, such as 100°C, and dried for 15-25min, such as 20min.

[0067] like Figure 4As shown, as an example, after forming the lower electrode layer 101, the step of forming a second interface layer 107 is also included, and the second interface layer 107 is formed on the lower surface of the organic light conversion layer 102. The specific steps of forming the second interface layer 107 include: dispersing the quantum dots or nanoparticles of the second interface layer 107 in a second solvent to form a second dispersion; applying the second dispersion on the lower electrode layer 101 by a solution method to form the second interface layer. As an example, the solution method includes at least one of scraping, inkjet printing, screen printing and slit coating; as an example, the thickness of the second interface layer is between 10nm-100nm, for example, it can be 15nm, 20nm, 60nm, 80nm, etc. Optionally, after coating the above film layer, it is placed in an oven at 80℃-120℃, such as 100℃, and dried for 3-15 minutes, such as 5 minutes. As an example, the material of the second interface layer includes at least one of TiO2, ZnO, AZO (Al-doped ZnO), MZO (Mg-doped ZnO), SnO2 and PEIE (name: ethoxylated polyethyleneimine); the second solvent includes at least one of water, ethanol, isopropanol and butanol.

[0068] like Figure 1 , Figure 5 and Figure 6 As shown, the next step S3 is to prepare an upper electrode layer 103 (such as Figure 5 as shown).

[0069] The upper electrode layer 103 is a transparent conductive oxide film (TCO), and as an example, the transparent conductive oxide film includes at least one of an ITO (indium tin oxide) layer, an IZO (indium zinc oxide) layer, and an IWO (tungsten-doped indium oxide) layer. The upper electrode layer 103 is preferably formed by a low-damage sputtering process.

[0070] like Figure 6As shown, as an example, after forming the organic light conversion layer 102, the step of forming a first interface layer 106 is also included, and the first interface layer 106 is formed on the upper surface of the organic light conversion layer 102. That is, the upper electrode layer 103 is formed on the first interface layer 106. The specific steps of forming the first interface layer 106 include: dispersing the quantum dots or nanoparticles of the first interface layer 106 in a first solvent to form a first dispersion; using a solution method to apply the first dispersion on the light conversion layer to form the first interface layer 106. Optionally, the solution method includes at least one of blade coating, inkjet printing, screen printing and slit coating. As an example, the thickness of the first interface layer 106 is between 5nm-100nm, for example, it can be 8nm, 20nm, 50nm, 80nm, etc. In addition, optionally, after the above film layer is coated, it is placed in an oven at 80℃-120℃, such as 100℃, and dried for 2-10 minutes, such as 10 minutes. As an example, the material of the first interface layer 106 includes at least one of Se, MoO3, WO3, NiO, V2O5, PEDOT:PSS (named: poly(3,4-ethylenedioxythiophene)-poly(styrene sulfonate)); the first solvent includes at least one of water, ethanol, isopropanol and butanol.

[0071] like Figure 1 , Figure 7 and Figure 8 As shown, the next step is to perform step S4, to prepare a packaging layer 104 (such as Figure 7 As shown in FIG. 1 ), the encapsulation layer 104 is formed by alternately stacking at least two groups of first encapsulation layers 104a and second encapsulation layers 104b (as shown in FIG. 1 ). Figure 8 As shown), the material of the first packaging layer 104a includes parylene or polyimide, and the material of the second packaging layer 104b includes aluminum oxide, silicon dioxide or silicon nitride.

[0072] like Figure 8 As shown, the encapsulation layer 104 is formed by alternately stacking 3 to 5 groups of the first encapsulation layers 104a and the second encapsulation layers 104b. Figure 8As shown in the figure, the encapsulation layer 104 is formed by alternating stacking of 4 groups of the first encapsulation layer 104a and the second encapsulation layer 104b, the thickness of the first encapsulation layer is between 500nm and 1000nm, for example, it can be 500nm, 700nm, 800nm, 1000nm, and the thickness of the second encapsulation layer is between 10nm and 50nm, for example, it can be 10nm, 20nm, 30nm, 40nm, 50nm. The use of the encapsulation layer 104 can effectively prevent damage to the organic light conversion layer 102 when the scintillator layer 105 is subsequently formed, so the thickness of the encapsulation layer cannot be too thin, too thin can not effectively protect the organic light conversion layer 102, too thick will block light and reduce the sensitivity of the detector, so arranging 3 to 5 groups of the first encapsulation layer 104a and the second encapsulation layer 104b to alternately stack to form the encapsulation layer 104 can not only effectively protect the organic light conversion layer 102, but also minimize the side effect of blocking light.

[0073] As an example, the first encapsulation layer 104a can be formed by a CVD process; when the material of the second encapsulation layer 104b is an aluminum oxide material, the second encapsulation layer 104b can be formed by an ALD process; when the material of the second encapsulation layer 104b is a silicon dioxide material or a silicon nitride material, the second encapsulation layer 104b can be formed by a PVD process. In this way, the formed encapsulation layer 104 has a high density and a simple process, which is easy to implement. In this embodiment, it is preferred that the material of the first encapsulation layer 104a is parylene, the material of the second encapsulation layer 104b is aluminum oxide, and the encapsulation layer 104 is formed by alternating stacking of 4 groups of the first encapsulation layer 104a and the second encapsulation layer 104b.

[0074] like Figure 1 and Fig. 9 As shown, step S5 is finally performed to prepare a scintillator layer 105 on the encapsulation layer 104. The material of the scintillator layer 105 includes Ca 1-x Sr x I2 or Ca 1-x Sr x I2:yEu 2+ , where 0≤x≤1, 0.01%≤y≤5%.

[0075] The method of forming the scintillator layer 105 is not limited in this embodiment, and for example, a thermal evaporation process, an electron beam evaporation process, etc. may be used. Based on the specific device size and process efficiency, this embodiment preferably uses a thermal evaporation process to prepare the scintillator layer 105, and the thermal evaporation temperature is between 600°C and 800°C according to the material of the scintillator layer 105.

[0076] As an example, Ca was prepared by thermal evaporation. 1-x Srx The main raw materials used in the scintillator layer 105 of I2 include CaI2 and SrI2; CaI2 is prepared by evaporation 1-x Sr x I2:yEu 2+ The main materials used in the scintillator layer 105 include CaI2, SrI2 and EuI2.

[0077] As an example, the scintillator layer 105 is prepared by a thermal evaporation process. Before evaporation, the furnace can be evacuated to prevent the main raw material used in the thermal evaporation from being oxidized during the evaporation process. The vacuum degree is 10 -2 Pa~10 -3 Pa. In addition, in order to further prevent the main raw material used for evaporation from being oxidized during the evaporation process, a reducing gas can be introduced into the furnace during thermal evaporation to prepare the scintillator layer 105. The reducing gas generally includes at least one of H2, CH4 and NH3. Taking safety into consideration, when using reducing gas, pure reducing gas is generally not used, that is, pure H2, CH4 and NH3 are not used, so a protective gas, such as N2, is also introduced into the furnace at the same time. In this embodiment, it is preferred that the reducing gas is H2 and the protective gas is N2, and the volume of H2 accounts for between 5% and 75% of the mixed gas of H2 and N2. During the thermal evaporation process, the vacuum degree of the evacuated furnace will generally decrease due to the introduction of reducing gas and protective gas, for example, from the initial 10 - 2 Pa~10 -3 Pa down to 10 2 Pa~10 3 As an example, when the reducing gas is introduced into the furnace, the flow rate of the reducing gas is between 10cc / min and 100cc / min.

[0078] When the scintillator layer 105 is formed by thermal evaporation, the organic light conversion layer 102 will be damaged. In particular, the use of reducing gas will destroy the organic light conversion layer 102 . Therefore, the encapsulation layer 104 is used to effectively protect the scintillator layer 105 .

[0079] When iodide is evaporated, the chemical formula may deviate from the ideal situation. For example, if a scintillator layer of CaI2 needs to be formed, the scintillator layer formed by thermal evaporation is generally CaI2. 2-z In this embodiment, when the scintillator layer is formed by thermal evaporation, a compensation raw material single substance I2 is added at the same time as the main raw material, and the mass ratio of the compensation raw material to the main raw material is between 0.1% and 0.5%.

[0080] As an example, when the scintillator layer 105 is a CaI2 scintillator layer, it is formed by a thermal evaporation process, the main raw material used in the evaporation is CaI2, the compensation raw material is a single substance I2, and the mass ratio of the two is 0.2%; the evaporation temperature is between 700°C and 800°C; the evaporation causes the vacuum degree in the furnace to be drawn to 2×10 -2 Pa; during evaporation, H2 and N are introduced into the furnace 2， The volume of H2 accounts for 10% of the mixed gas of H2 and N2, and the flow rate of H2 is 50 cc / min.

[0081] As an example, when the scintillator layer 105 is CaI2:yEu 2+ The scintillator layer is formed by co-evaporation process. The main raw materials used in the evaporation are CaI2 and EuI2, and the compensation raw material is single substance I2, and the mass ratio of the two is 0.2%; the evaporation temperature is between 700℃ and 800℃; the evaporation makes the vacuum degree in the furnace reach 2×10 -2 Pa; during evaporation, H2 and N are introduced into the furnace 2， The volume of H2 accounts for 10% of the mixed gas of H2 and N2, and the flow rate of H2 is 50 cc / min.

[0082] As an example, when the scintillator layer 105 is a SrI2 scintillator layer, it is formed by a thermal evaporation process, the main raw material used in the evaporation is SrI2, the compensation raw material is a single substance I2, and the mass ratio of the two is 0.2%; the evaporation temperature is between 600°C and 700°C, preferably 645°C; the evaporation is performed to evacuate the vacuum degree in the furnace to 2×10 -2 Pa; during evaporation, H2 and N are introduced into the furnace 2， The volume of H2 accounts for 10% of the mixed gas of H2 and N2, and the flow rate of H2 is 50 cc / min.

[0083] As an example, when the scintillator layer 105 is SrI2:yEu 2+ The scintillator layer is formed by a co-evaporation process. The main raw materials used in the evaporation are SrI2 and EuI2, and the compensation raw material is single substance I2, and the mass ratio of the two is 0.2%; the evaporation temperature is between 600℃ and 700℃, preferably 645℃; the evaporation makes the vacuum degree in the furnace reach 2×10 -2 Pa; during evaporation, H2 and N are introduced into the furnace 2， The volume of H2 accounts for 10% of the mixed gas of H2 and N2, and the flow rate of H2 is 50 cc / min.

[0084] As an example, when the scintillator layer 105 is Ca 1-x Sr xWhen the I2 scintillator layer is formed, where 0<x<1, it is formed by a co-evaporation process. The main raw materials used in the evaporation are SrI2 and CaI2, and the compensation raw material is a single substance I2, and the mass ratio of the two is 0.2%; the evaporation temperature is between 600℃ and 800℃, and the evaporation temperature increases with Ca 1-x Sr x As the Sr content in I2 increases, the temperature decreases, but it is not lower than the temperature during SrI2 evaporation. For example, when Ca 0.9 Sr 0.1 When the I2 scintillator layer is formed, the evaporation temperature is 750℃; the vacuum degree in the furnace is drawn to 2×10 -2 Pa; during evaporation, H2 and N are introduced into the furnace 2， The volume of H2 accounts for 10% of the mixed gas of H2 and N2, and the flow rate of H2 is 50 cc / min.

[0085] As an example, when the scintillator layer 105 is Ca 1-x Sr x I2:yEu 2+ When the scintillator layer is formed, 0<x<1, the co-evaporation process is adopted, the main raw materials used in the evaporation are SrI2, CaI2 and EuI2, the compensation raw material is single substance I2, and the mass ratio of the two is 0.2%; the evaporation temperature is between 600℃~800℃, and the evaporation temperature increases with Ca 1-x Sr x I2:yEu 2+ As the Sr content increases, the temperature decreases, but it is not lower than the temperature during SrI2 evaporation. For example, when Ca 0.9 Sr 0.1 I2:yEu 2+ When the scintillator layer is formed, the evaporation temperature is 750°C; the vacuum degree in the furnace is drawn to 2×10 -2 Pa; during evaporation, H2 and N are introduced into the furnace 2， The volume of H2 accounts for 10% of the mixed gas of H2 and N2, and the flow rate of H2 is 50 cc / min.

[0086] For the relevant features and description of the method for preparing the indirect flat panel detector of this embodiment, please refer to the relevant description of the indirect flat panel detector of this embodiment, which will not be repeated here.

[0087] In summary, the indirect flat-panel detector and its preparation method of the present invention adopt an organic light conversion layer to replace the existing amorphous Si to realize photoelectric conversion. Since the response spectrum of the organic light conversion layer is very wide, the light response of the photosensitive layer of the flat-panel detector can be broadened to the blue light region, and the response in the blue light region is similar to that of 550nm yellow-green light. Based on this, the present invention further arranges a Ca 1-x Sr xI2 or Ca 1-x Sr x I2:yEu 2+ The scintillator layer of the material has a significantly improved light yield in the blue light region compared to the CsI:Tl scintillator material, thereby effectively improving the light response of the indirect flat-panel detector, greatly improving the sensitivity of the flat-panel detector, and enabling the flat-panel detector to be used in low-dose application scenarios; in addition, by providing the encapsulation layer, the damage to the organic light conversion layer when forming the scintillator layer can be effectively prevented to ensure the sensitivity of the detector. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has a high industrial utilization value.

[0088] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. An indirect flat panel detector, characterized in that: The indirect flat panel detector comprises: substrate; A lower electrode layer is formed on the substrate; An organic light conversion layer is formed on the lower electrode layer, and the raw materials for preparing the organic light conversion layer include a P-type organic photoelectric material, an N-type organic photoelectric material, and an organic solvent for dissolving the P-type organic photoelectric material and the N-type organic photoelectric material; An upper electrode layer, formed on the organic light conversion layer; An encapsulation layer is formed on the upper electrode layer, the encapsulation layer is formed by alternately stacking 3 to 5 groups of first encapsulation layers and second encapsulation layers, the material of the first encapsulation layer includes parylene or polyimide, and the material of the second encapsulation layer includes aluminum oxide, silicon dioxide or silicon nitride; the thickness of the first encapsulation layer is between 500 nm and 1000 nm, and the thickness of the second encapsulation layer is between 10 nm and 50 nm; A scintillator layer is formed on the encapsulation layer, wherein the material of the scintillator layer includes Ca 1-x Sr x I2 or Ca 1-x Sr x I2:yEu 2 + , wherein 0≤x≤1, 0.01%≤y≤5%, the scintillator layer is prepared by a thermal evaporation process, the temperature of the thermal evaporation is between 600°C and 800°C, and when the scintillator layer is prepared by thermal evaporation, a reducing gas is introduced into the furnace, and the reducing gas includes at least one of H2, CH4 and NH3.

2. The indirect flat panel detector according to claim 1, characterized in that: The flat-panel detector also includes a first interface layer and a second interface layer, the first interface layer is located on the upper surface of the organic light conversion layer, and the second interface layer is located on the lower surface of the organic light conversion layer; the material of the first interface layer includes at least one of Se, MoO3, WO3, NiO, V2O5 and PEDOT:PSS, and the material of the second interface layer includes at least one of TiO2, ZnO, AZO, MZO, SnO2 and PEIE; the thickness of the first interface layer is between 5nm and 100nm, and the thickness of the second interface layer is between 10nm and 100nm.

3. The indirect flat panel detector according to claim 1, characterized in that: The P-type organic photoelectric material includes at least one of P3HT and PCPDTBT; the N-type organic photoelectric material includes at least one of PC61BM and PC71BM; the organic solvent includes at least one of o-xylene, chloroform and tetralin; the thickness of the organic light conversion layer is between 100nm and 2000nm.

4. The indirect flat panel detector according to claim 1, characterized in that: The material of the scintillator layer includes CaI2, CaI2:yEu 2+ 、SrI2、SrI2:yEu 2+ , Ca 0.9 Sr 0.1 I2 or Ca 0.9 Sr 0.1 I2:yEu 2+ .

5. A method for preparing an indirect flat panel detector, characterized in that: The preparation method comprises the following steps: Providing a substrate, and preparing a lower electrode layer on the substrate; Dissolving a P-type organic photoelectric material and an N-type organic photoelectric material in an organic solvent to prepare a light conversion material liquid, and preparing an organic light conversion layer on the lower electrode layer based on the light conversion material liquid; Preparing an upper electrode layer on the organic light conversion layer; A packaging layer is prepared on the upper electrode layer, wherein the packaging layer is formed by alternately stacking at least two groups of first packaging layers and second packaging layers, wherein the material of the first packaging layer includes parylene or polyimide, and the material of the second packaging layer includes aluminum oxide, silicon dioxide or silicon nitride, and the packaging layer is formed by alternately stacking three to five groups of the first packaging layers and the second packaging layers, wherein the thickness of the first packaging layer is between 500 nm and 1000 nm, and the thickness of the second packaging layer is between 10 nm and 50 nm; A scintillator layer is prepared on the encapsulation layer, wherein the material of the scintillator layer includes Ca 1-x Sr x I2 or Ca 1-x Sr x I2:yEu 2 + , wherein 0≤x≤1, 0.01%≤y≤5%; wherein the scintillator layer is prepared by a thermal evaporation process, the temperature of the thermal evaporation is between 600°C and 800°C, and when the scintillator layer is prepared by thermal evaporation, a reducing gas is introduced into the furnace, and the reducing gas includes at least one of H2, CH4 and NH3.

6. The method for preparing an indirect flat panel detector according to claim 5, characterized in that: After forming the lower electrode layer, the step of forming a second interface layer is also included, and the second interface layer is formed on the lower surface of the organic light conversion layer; after forming the organic light conversion layer, the step of forming a first interface layer is also included, and the first interface layer is formed on the upper surface of the organic light conversion layer.

7. The method for preparing an indirect flat panel detector according to claim 5, characterized in that: The first encapsulation layer is formed by a CVD process; the second encapsulation layer of the aluminum oxide material is formed by an ALD process; and the second encapsulation layer of the silicon dioxide material or the silicon nitride material is formed by a PVD process.

8. The method for preparing an indirect flat panel detector according to claim 5, characterized in that: The reducing gas is H2, and N2 is also introduced into the furnace, and the volume of H2 accounts for between 5% and 75% of the mixed gas.

9. The method for preparing an indirect flat panel detector according to claim 8, characterized in that: The flow rate of the reducing gas introduced into the furnace is between 10cc / min and 100cc / min.

10. The method for preparing an indirect flat panel detector according to claim 5, characterized in that: Thermal evaporation preparation of Ca 1-x Sr x The main raw materials used in the scintillator layer of I2 include CaI2 and SrI2; CaI2 is prepared by evaporation 1-x Sr x I2:yEu 2+ The main materials used in the scintillator layer include CaI2, SrI2 and EuI2.

11. The method for preparing an indirect flat panel detector according to claim 10, characterized in that: When the scintillator layer is prepared by thermal evaporation, a compensation raw material is also included. The compensation raw material is a single substance I2, and the mass ratio of the compensation raw material to the main raw material is between 0.1% and 0.5%.

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