X-ray detector

Abstract

The present invention provides an X-ray detector comprising: a first electrode and a second electrode on a substrate; and a photoelectric material layer formed between the first electrode and the second electrode and containing perovskite, in which the photoelectric material layer includes: a first photoelectric layer formed of a first perovskite having a first crystal size; and a second photoelectric layer formed on the first photoelectric layer using a second perovskite having a second crystal size larger than the first crystal size.

Description

Technical Field

[0001] The invention relates to an X-ray detector. Background Art

[0002] Recently, digital detectors are widely used in X-ray imaging.

[0003] X-ray detectors are classified into indirect conversion and direct conversion methods. In the indirect conversion method, X-rays are converted into visible light using a phosphor, and then detected by converting the visible light into an electrical signal. In contrast, in the direct conversion method, photoelectric materials (photoconductors) are used that absorb X-rays and directly generate electrical signals.

[0004] Perovskite has recently attracted much attention as a photoelectric material. However, according to research so far, there are limitations in using perovskite as a photoelectric material for X-ray detectors. Summary of the invention

[0005] The technical problem of the present invention is to provide a solution that can effectively use perovskite as a photoelectric material for X-ray detectors.

[0006] In order to achieve the technical problem as described above, the present invention provides an X-ray detector, comprising: a first electrode and a second electrode on a substrate; and a photoelectric material layer formed between the first electrode and the second electrode and containing perovskite, wherein the photoelectric material layer comprises: a first photoelectric layer formed using a first perovskite having a first crystal size; and a second photoelectric layer formed on the first photoelectric layer using a second perovskite having a second crystal size larger than the first crystal size.

[0007] The first crystal size of the first perovskite may be 1 μm to 3 μm.

[0008] The second crystal size of the second perovskite may be 3 μm to 10 μm.

[0009] The first photovoltaic layer may have a columnar crystal structure, and the second photovoltaic layer may have a cubic crystal structure.

[0010] In the second photoelectric layer, the second crystal size of the second perovskite may gradually increase as it moves away from the substrate.

[0011] The thickness of the second photovoltaic layer may be greater than the thickness of the first photovoltaic layer.

[0012] The thickness of the first photoelectric layer may be 1 μm to 50 μm, and the thickness of the second photoelectric layer may be 60 μm to 500 μm.

[0013] The perovskite may be CsPbBr3, Cs2AgBiBr6, MAPbI3 or MAPbBr3.

[0014] According to the present invention, when using perovskite to form a photovoltaic material layer, the lower first photovoltaic layer is formed using tiny columnar perovskite crystals, and the upper second photovoltaic layer is formed using cubic perovskite crystals whose size gradually increases toward the upper direction.

[0015] Therefore, the photovoltaic material layer formed using perovskite can have excellent electrical properties while fully ensuring adhesion to the substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a diagram schematically showing an X-ray detector according to an embodiment of the present invention.

[0017] Figure 2 is a cross-sectional view schematically showing an X-ray detector according to an embodiment of the present invention.

[0018] Figure 3 is an enlarged cross-sectional view showing a photovoltaic material layer according to an embodiment of the present invention.

[0019] [Description of Reference Numerals] 10: X-ray detector 100: Substrate 130: First electrode 140: Photoelectric material layer 141: First Photoelectric Layer 141a: The first perovskite crystal 143: Second Photoelectric Layer 143a: Second perovskite crystal 150: Second electrode P: Pixel DETAILED DESCRIPTION

[0020] Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

[0021] Figure 1 is a diagram schematically showing an X-ray detector according to an embodiment of the present invention. Figure 2 is a cross-sectional view schematically showing an X-ray detector according to an embodiment of the present invention. Figure 3 is an enlarged cross-sectional view showing a photovoltaic material layer according to an embodiment of the present invention.

[0022] In addition, Figure 3 In the figure, for the convenience of explanation, the first electrode and the second electrode located at the lower part and the upper part of the photoelectric material layer are omitted.

[0023] Reference Figures 1 to 3 The X-ray detector 10 according to the embodiment of the present invention corresponds to a direct conversion type X-ray detector equipped with a photoelectric material layer 140 .

[0024] The X-ray detector 10 may include a sensor panel 100 , a driving circuit portion driving the sensor panel 100 , and a power supply circuit 300 supplying a driving voltage (or power supply voltage) for driving the X-ray detector 10 .

[0025] The sensor panel 100 may be a direct conversion type sensor panel 100 that directly converts incident X-rays into electrical signals.

[0026] Although not specifically shown, the sensor panel 100 may include an effective area which is an area that actually receives and detects X-rays and a non-effective area located outside the effective area.

[0027] In the active area, a pixel array composed of a plurality of pixels P is arranged on the substrate 110 . The plurality of pixels P may be arranged in a matrix along a plurality of row lines and a plurality of column lines.

[0028] Furthermore, a plurality of scan wirings (or gate wirings) SL extending along a plurality of row lines and a plurality of signal transmission wirings (or data wirings) RL extending along a plurality of column lines may be arranged on the substrate 110. Such scan wirings SL and signal transmission wirings RL may be connected to corresponding pixels P.

[0029] In addition, in the present embodiment, the substrate 110 may be formed of a complementary metal oxide semiconductor (CMOS) substrate, a glass substrate, or a plastic substrate having a flexible property, but is not limited thereto.

[0030] The driving circuit part driving the sensor panel 100 may include a scanning circuit 220 and a reading circuit 230 .

[0031] The scanning circuit 220 applies a scanning signal of a conduction level by sequentially scanning the scanning wiring SL. Thus, each row line is sequentially selected, and the data as the electrical signal stored in the pixel P located in the selected row line can be output through the corresponding signal transmission wiring RL. In addition, the reading circuit 230 can receive the data stored in the pixel P through the signal transmission wiring RL.

[0032] Each pixel P of the sensor panel 100 may be provided with a photoelectric element PC that detects X-rays and generates a corresponding electrical signal.

[0033] In this regard, the optoelectronic element PC may include: a first electrode (or pixel electrode) 130 as a lower electrode formed on a substrate 110 ; a second electrode (or common electrode) 150 as an upper electrode located on the first electrode 130 ; and a photoelectric material layer 140 arranged between the first electrode 130 and the second electrode 150 .

[0034] The first electrode 130 may be formed in a form of being patterned in units of pixels corresponding to the respective pixels P.

[0035] For example, the electro-optical substance layer 140 formed on the first electrode 130 may be continuously formed along a plurality of pixels P actually arranged in the active area. In other words, the electro-optical substance layer 140 may be formed corresponding to a plurality of pixels P arranged in the active area.

[0036] As the photoelectric material forming such a photoelectric material layer 140 , perovskite can be used.

[0037] In this regard, perovskite corresponds to a substance having a crystal structure of ABX3, wherein A may be a monovalent cation, B may be a metal cation, and X may be a halogen anion.

[0038] For example, such perovskite may be CsPbBr3, Cs2AgBiBr6, MAPbI3, MAPbBr3, but is not limited thereto.

[0039] In addition, for example, the photoelectric material layer 140 of perovskite may be formed by a solution process, which will be described in more detail below.

[0040] For example, the second electrode 150 formed on the photoelectric material layer 140 may be continuously formed along a plurality of pixels P actually arranged in the active area. In other words, the second electrode 150 may be formed corresponding to a plurality of pixels P arranged in the active area. A bias voltage Vb (ie, a reverse voltage) may be applied to such a second electrode 150.

[0041] In order to realize charge generation based on the photoelectric effect in the photoelectric element PC configured as described above, a pixel voltage Vp as a driving voltage (or a first driving voltage) may be applied to the first electrode 130, and a bias voltage Vb as a driving voltage (or a second driving voltage) may be applied to the second electrode 150. Thus, the photoelectric element PC may be applied with a difference voltage between the bias voltage Vb and the pixel voltage Vp, and if X-rays are incident in this state, corresponding charges are generated by the photoelectric effect, and the generated charges may be collected in the first electrode 130.

[0042] Such a driving voltage may be generated and provided in the power supply circuit 300. In this regard, the power supply circuit 300 may generate a pixel voltage Vp and a bias voltage Vb and output them to the sensor panel 100.

[0043] In addition, in this embodiment, for example, Figure 3 As shown, the photovoltaic material layer 140 formed of perovskite may be constructed using a double-layer structure. In other words, the photovoltaic material layer 140 may include a first photovoltaic layer 141 as a lower layer and a second photovoltaic layer 143 as an upper layer.

[0044] The first photoelectric layer 141 and the second photoelectric layer 143 may have different perovskite crystal structures.

[0045] In this regard, for example, the crystals (or first crystals) 141a of the perovskite (or first perovskite) forming the first photoelectric layer 141 may be formed into a columnar structure as microcrystals, and the crystals (or second crystals) 143a of the perovskite (or second perovskite) forming the second photoelectric layer 143 may be formed into a cubic structure. As described above, since each of the first photoelectric layer 141 and the second photoelectric layer 143 is formed into a crystal structure of perovskite, the photoelectric material layer 140 may have excellent electrical characteristics.

[0046] Regarding the structure of the first perovskite crystal 141 a forming the first photoelectric layer 141 , for example, the size (or diameter) of the crystal 141 a is preferably about 1 μm to 3 μm.

[0047] In this regard, since the thermal expansion rate of the perovskite is greatly different from that of the substrate 110 in its characteristics, the photoelectric material layer 140 may be removed (or peeled off) from the substrate 110 depending on the temperature.

[0048] In this regard, for the first photoelectric layer 141 serving as the lower layer of the photoelectric material layer 140, by forming crystals 141a having a columnar structure with a tiny size of 1μm~3μm, the adhesion characteristics of the photoelectric material layer 140 are improved and the adhesion of the photoelectric material layer 140 to the substrate 110 can be effectively ensured.

[0049] Regarding the formation of such a first photoelectric layer 141, for example, by repeatedly applying a solution of a perovskite precursor (e.g., CsBr, PbBr2, etc.) mixed with a solvent (e.g., a polar solvent) to a substrate and curing it, microcrystals 141a having a columnar structure can be grown and the first photoelectric layer 141 can be formed.

[0050] In addition, the thickness of the first photoelectric layer 141 may be appropriately set in consideration of the X-ray imaging device (or purpose) to which the X-ray detector 10 is applied. For example, the thickness of the first photoelectric layer 141 may be about 1 μm to 50 μm, and may preferably be about 1 μm to 20 μm, but is not limited thereto.

[0051] Regarding the structure of the second perovskite crystals 143 a forming the second photoelectric layer 143 , for example, the size (or diameter) of the crystals 143 a is preferably about 3 μm to 10 μm.

[0052] In this regard, if the size of the second perovskite crystal 143a becomes larger, the porosity increases, thereby reducing the adhesion to the substrate 110. In addition, as described above, since the thermal expansion coefficient of perovskite is greatly different from that of the substrate 110 in its characteristics, the photoelectric material layer 140 may be removed (or peeled off) from the substrate 110 depending on the temperature. In view of this, the size of the second perovskite crystal 143a is preferably 10 μm or less.

[0053] Also, if the size of the second perovskite crystal 143 a is less than 3 μm, it is difficult to maintain the cubic structure. In view of this, the second perovskite crystal 143 a is preferably 3 μm or more.

[0054] Finally, considering the porosity and cubic crystal structure within the photoelectric material layer 140 , the size of the second perovskite crystal 143 a may be set to be approximately 3 μm to 10 μm.

[0055] Also, in order to realize the second perovskite crystals 143 a having the above-mentioned size, the size of the perovskite powder mixed with the solvent before coating may be about 3 μm to 7 μm.

[0056] In addition, if Figure 3 As shown, within the second photovoltaic layer 143 , the second perovskite crystals 143 a may be configured such that their sizes gradually increase toward an upper direction (ie, away from the substrate 110 ).

[0057] In other words, the size of the second perovskite crystals 143a formed in the lower portion of the second photovoltaic layer 143 close to the substrate 110 may be relatively small, and the size of the second perovskite crystals 143a formed in the upper portion of the second photovoltaic layer 143 far from the substrate 110 may be larger.

[0058] As described above, by forming small-sized perovskite crystals 143 a having relatively large adhesion characteristics in a portion of the second photovoltaic layer 143 located close to the substrate 110 , adhesion of the photovoltaic material layer 140 with respect to the substrate 110 can be effectively ensured.

[0059] As described above, regarding the structure for realizing a gradual increase in the size of the crystal 143a from the photoelectric material layer 140 toward the upper direction, during the curing process after coating a solution mixed with perovskite powder and a solvent, heat is applied to the substrate 110 (more specifically, heat is applied to the lower part of the substrate 110), so that the solution close to the substrate 110 side evaporates first, thereby causing the size of the second perovskite crystal 143a to gradually increase in the upper direction.

[0060] Regarding the curing conditions for such a curing process, for example, the curing process may be performed for about 10 to 20 hours at a temperature of normal temperature to 90 degrees Celsius for the applied perovskite solution.

[0061] In addition, the thickness of the second photovoltaic layer 143 including the second perovskite crystals 143 a can be appropriately set in consideration of the X-ray imaging device (or purpose) to which the X-ray detector 10 is applied.

[0062] In this regard, the second photovoltaic layer 143 may be formed to be thicker than the first photovoltaic layer 141 . For example, the thickness of the second photovoltaic layer 143 may be about 60 μm to 500 μm, but is not limited thereto.

[0063] As described above, in an embodiment of the present invention, when perovskite is used to form the photoelectric material layer 140, the lower first photoelectric layer 141 is formed by tiny columnar perovskite crystals, and the upper second photoelectric layer 143 is formed by cubic perovskite crystals whose size gradually increases toward the upper direction.

[0064] Therefore, the photovoltaic material layer 140 formed of perovskite can have excellent electrical characteristics while fully ensuring adhesion to the substrate.

[0065] The above-described embodiment of the present invention is an example of the present invention, and the present invention can be freely modified within the scope of the gist of the present invention. Therefore, the present invention includes the modifications of the present invention within the scope of the appended claims and the equivalents thereof.

Claims

1. An X-ray detector, comprising: a first electrode and a second electrode on a substrate; as well as The photoelectric material layer is formed between the first electrode and the second electrode and contains perovskite. Wherein, the photoelectric material layer comprises: a first photovoltaic layer formed using a first perovskite having a first crystal size; and A second photovoltaic layer is formed on the first photovoltaic layer using a second perovskite having a second crystal size larger than the first crystal size.

2. The X-ray detector according to claim 1, wherein: The first crystal size of the first perovskite is 1 μm to 3 μm.

3. The X-ray detector according to claim 1, wherein: The second crystal size of the second perovskite is 3 μm to 10 μm.

4. The X-ray detector according to claim 1, wherein: The first photovoltaic layer has a columnar crystal structure, and the second photovoltaic layer has a cubic crystal structure.

5. The X-ray detector according to claim 3, wherein: In the second photoelectric layer, the second crystal size of the second perovskite gradually increases as it moves away from the substrate.

6. The X-ray detector according to claim 1, wherein: The thickness of the second photovoltaic layer is greater than the thickness of the first photovoltaic layer.

7. The X-ray detector according to claim 6, wherein: The thickness of the first photoelectric layer is 1 μm to 50 μm. The thickness of the second photoelectric layer is 60 μm to 500 μm.

8. The X-ray detector according to claim 1, wherein: The perovskite is CsPbBr3, Cs2AgBiBr6, MAPbI3 or MAPbBr3.

Images