Detection element, manufacturing method thereof, flat panel detector

A detection element, a manufacturing method thereof and a flat panel detector are disclosed. The detection element includes: a base substrate; a photodiode on the base substrate, the photodiode includes: a first electrode on the base substrate; a photoelectric conversion layer on a side of the first electrode away from the base substrate; a transparent electrode and a second electrode electrically connected with the transparent electrode on a side of the photoelectric conversion layer away from the first electrode. Besides, an orthographic projection of the photoelectric conversion layer on the base substrate completely falls within an orthographic projection of the first electrode on the base substrate; the photoelectric conversion layer includes a sidewall, an orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate is at least partially overlapped with an orthographic projection of the second electrode on the base substrate.

The present application claims priority of China Patent application No. 201710967141.4 filed on Oct. 17, 2017, the content of which is incorporated in its entirety as portion of the present application by reference herein.

TECHNICAL FIELD

At least one embodiment of the present disclosure relates to a detection element, a manufacturing method thereof, and a flat panel detector.

BACKGROUND

X-ray detection is widely used in modern medical image detection. Currently, the most advanced direct digital radiography (DR) is a technology which adopts an one-dimensional or two-dimensional X-ray detector to directly convert X-ray information into digital image information under the control of a computer with image processing function. A two-dimensional flat X-ray panel detector (FPXD) used in the current DR equipment includes a direct flat panel detector and an indirect flat panel detector.

SUMMARY

At least one embodiment of the present disclosure provides a detection element, a manufacturing method thereof, and a flat panel detector.

At least one embodiment of the present disclosure provides a detection element, including: a photodiode on a base substrate; the photodiode including: a first electrode on the base substrate; a photoelectric conversion layer on a side of the first electrode away from the base substrate; a transparent electrode and a second electrode electrically connected with the transparent electrode on a side of the photoelectric conversion layer away from the first electrode, wherein an orthographic projection of the photoelectric conversion layer on the base substrate completely falls within an orthographic projection of the first electrode on the base substrate, the photoelectric conversion layer includes a sidewall, and an orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate is at least partially overlapped with an orthographic projection of the second electrode on the base substrate.

For example, an orthographic projection of the transparent electrode on the base substrate completely falls within the orthographic projection of the photoelectric conversion layer on the base substrate, and is not overlapped with the orthographic projection of the sidewall on the base substrate.

For example, a cross section of the photoelectric conversion layer taken in a direction perpendicular to the base substrate has a trapezoid shape, and a length of a base of the trapezoid shape close to the transparent electrode is smaller than that of a base of the trapezoid shape close to the first electrode.

For example, an orthographic projection of a portion of the photoelectric conversion layer not covered by the transparent electrode on the base substrate completely falls into the orthographic projection of the second electrode on the base substrate.

For example, the detection element further includes: a bias signal line on a side of the transparent electrode away from the photoelectric conversion layer. The bias signal line is electrically connected with the transparent electrode, and the second electrode is electrically connected with the bias signal line.

For example, an orthographic projection of the bias signal line on the base substrate is overlapped with a portion of the orthographic projection of the photoelectric conversion layer on the base substrate, and an orthographic projection of a portion of the photoelectric conversion layer not covered by the transparent electrode and the bias signal line on the base substrate completely falls into the orthographic projection of the second electrode on the base substrate.

For example, the detection element further includes: an insulating layer between the bias signal line and the transparent electrode. The insulating layer includes a via hole, and the bias signal line is electrically connected with the transparent electrode through the via hole.

For example, the second electrode is on a side of the insulating layer away from the transparent electrode.

For example, the second electrode and the bias signal line are in a same layer and materials of the second electrode and the bias signal line are the same.

For example, a material of the second electrode includes a light shielding material.

For example, the orthographic projection of the transparent electrode on the base substrate is not overlapped with the orthographic projection of the second electrode on the base substrate.

For example, the detection element further includes: a thin film transistor including a source electrode and a drain electrode, one of the source electrode and the drain electrode is the first electrode.

For example, the photodiode is a PIN type photodiode.

At least one embodiment of the present disclosure provides a manufacturing method of a detection element, including: forming a photodiode on a base substrate, and forming the photodiode including: forming a first electrode on the base substrate; forming a photoelectric conversion layer on a side of the first electrode away from the base substrate; and forming a transparent electrode and a second electrode electrically connected with the transparent electrode on a side of the photoelectric conversion layer away from the first electrode, an orthographic projection of the photoelectric conversion layer on the base substrate completely falls within an orthographic projection of the first electrode on the base substrate, the photoelectric conversion layer includes a sidewall, and an orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate is at least partially overlapped with an orthographic projection of the second electrode on the base substrate.

For example, an orthographic projection of the transparent electrode on the base substrate completely falls within the orthographic projection of the photoelectric conversion layer on the base substrate and is not overlapped with the orthographic projection of the sidewall on the base substrate, forming the second electrode includes: forming the second electrode on a side of a portion of the photoelectric conversion layer not covered by the transparent electrode away from the base substrate, such that an orthographic projection of the portion of the photoelectric conversion layer not covered by the transparent electrode on the base substrate completely falls within the orthographic projection of the second electrode on the base substrate.

For example, the manufacturing method of the detection element further includes: forming an insulating layer on a side of the transparent electrode away from the photoelectric conversion layer; patterning the insulating layer to form a via hole; forming a conductive layer on a side of the insulating layer away from the transparent electrode, the conductive layer being electrically connected with the transparent electrode through the via hole; and patterning the conductive layer to form a bias signal line and the second electrode which are electrically connected with each other, the bias signal line being electrically connected with the transparent electrode through the via hole.

For example, a material of the second electrode includes a light shielding material.

At least one embodiment of the present disclosure provides a flat panel detector, including a plurality of detection elements according to any one of the abovementioned embodiments, and the plurality of detection elements are arranged in an array.

For example, the flat panel detector is an indirect flat panel detector.

DETAILED DESCRIPTION

FIG. 1Ais a top view of a detection element included in a flat panel detector, andFIG. 1Bis a side view of the detection element illustrated byFIG. 1Ataken along a line AB. In order to clearly illustrate a plan view of a photoelectric conversion layer, a top electrode and a bottom electrode which are included in a photodiode, some insulating layers are omitted inFIG. 1A. As illustrated byFIG. 1AandFIG. 1B, the detection element of the flat panel detector includes a base substrate10; a gate line32extending in an X direction and a data line31extending in a Y direction which are disposed on the base substrate10; a thin film transistor disposed on the base substrate10, the thin film transistor includes a gate electrode22, a gate insulating layer16covering the gate electrode22, an active layer21on the gate insulating layer16, and source and drain electrodes11aand11b. The gate line32is connected with the gate electrode22to turn on or turn off the thin film transistor, and one of the source and drain electrodes11aand11bis connected with the data line31. In the figure, a case where the source electrode11ais connected with the data line31is shown as an example. The detection element of the flat panel detector further includes a photoelectric conversion layer12disposed on the drain electrode11b, the photoelectric conversion layer12uses the drain electrode11bas its bottom electrode11; a transparent top electrode13disposed on a side of the photoelectric conversion layer12away from the bottom electrode11; film layers such as a buffer layer17and a passivation layer19which are disposed on the transparent top electrode13; and a bias signal line14on a side of the film layers such as the buffer layer17and the passivation layer18away from the transparent top electrode13. The bias signal line14is electrically connected with the transparent top electrode13through a via hole15disposed in the film layers such as the buffer layer17and the passivation layer18. The detection element of the flat panel detector further includes a protective layer19disposed on a side of the bias signal line14away from the photoelectric conversion layer12. The photoelectric conversion layer12forms an electric field under a bias voltage input from the bias signal line14, and photoelectrons generated by the photoelectric conversion layer12after being irradiated are accumulated in the bottom electrode11by an external electric field, after the gate line32turns on the thin film transistor, the electrons accumulated in the bottom electrode11are read out through the data line31, and converted into a digital signal by a reading chip, and the digital signal is subjected to an image processing at a backend.

The photodiode illustrated byFIGS. 1A and 1Bis a PIN type photodiode including a P layer, an I layer, and an N layer, where the I layer is an intrinsic semiconductor layer or a doped layer of a near-intrinsic semiconductor having a low doping concentration.

In the study, the inventor(s) of the present application notices that: on the one hand, in a flat panel detector using a PIN type photodiode structure, the most important fact affecting the photoelectric characteristics of the flat panel detector is that a dark-state leakage current generated by the photoelectric conversion layer structure is relatively large. The main reasons for the dark-state leakage current of the photoelectric conversion layer include: deposition parameters of the P layer, the I layer, and the N layer need to be optimized; due to the limitation of etching process of the photoelectric conversion layer and the requirements for manufacturing a passivation layer and a resin layer process in subsequent processes, an etched sidewall of the photoelectric conversion layer is not perpendicular to the bottom electrode, but forms an angle of about 75 to 85 degrees with the bottom electrode, i.e., an angle between the sidewall of the photoelectric conversion layer and the bottom electrode is about 75 to 85 degrees. That is, as illustrated byFIG. 1B, due to the limitation of the etching process of the photoelectric conversion layer12and the top electrode13, and the deposition requirements of the film layer such as the resin buffer layer, a cross section of the photoelectric conversion layer12, which is finally formed, has a trapezoid shape, the angle between the sidewall of the photoelectric conversion layer12and the bottom electrode11cannot reach 90 degrees, and the top electrode13is located at a middle portion of an upper surface of the photoelectric conversion layer12. Therefore, after a bias voltage being applied to the top electrode13and the bottom electrode11located on both sides of the photoelectric conversion layer12, an ineffective bias voltage at the sidewall will generate a large leakage current. Upon the flat panel detector being in operation, the top electrode13is applied with a negative bias voltage, the bottom electrode11is applied with a positive voltage, and the structure of the photoelectric conversion layer12is similar to a capacitor, however, in a plane parallel to the base substrate10, because a size of the top electrode13is smaller than that of the bottom electrode11, an electric field at the sidewall of the photoelectric conversion layer12is weaker than an electric field at the middle position of the photoelectric conversion layer, which will cause a large leakage current, such that the final signal is affected, thereby affecting the leakage current of the entire structure of the detection element, and finally lowering the photoelectric characteristics of the flat panel detector.

On the other hand, an indirect flat panel detector converts X-ray light into visible light by using a scintillation layer, and the converted visible light is relatively divergent. Therefore, the irradiation of the divergent light on the sidewall of an imaging unit (the photoelectric conversion layer) has disadvantageous influence on the image quality.

Embodiments of the present disclosure provide a detection element, a manufacturing method thereof, and a flat panel detector. The detection element includes: a base substrate; a photodiode on the base substrate, the photodiode including: a first electrode on the base substrate; a photoelectric conversion layer on a side of the first electrode away from the base substrate; and a transparent electrode and a second electrode electrically connected with the transparent electrode which are on a side of the photoelectric conversion layer away from the first electrode. An orthographic projection of the photoelectric conversion layer on the base substrate completely falls within an orthographic projection of the first electrode on the base substrate, the photoelectric conversion layer includes a sidewall, the orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate is at least partially overlapped with an orthographic projection of the second electrode on the base substrate. The detection element can effectively reduce the dark-state leakage current generated by the photoelectric conversion layer, thereby improving the photoelectric characteristics of the detection element and the flat panel detector including the detection element.

Hereinafter, the detection element, the manufacturing method thereof and the flat panel detector provided by the embodiments of the present disclosure will be described with reference to the accompanying drawings.

FIG. 2Ais a schematic plan view of a detection element according to an embodiment of the present disclosure, andFIG. 2Bis a schematic cross-sectional view of the detection element illustrated byFIG. 2Ataken along a line CD. In order to clearly illustrate a plan view of a first electrode, a transparent electrode, and a second electrode, some insulating layers are omitted inFIG. 2A. As illustrated byFIGS. 2A and 2B, a detection element according to an embodiment of the present disclosure includes a base substrate100, a photodiode1200on the base substrate100, the photodiode1200includes a first electrode110on the base substrate100, a photoelectric conversion layer120located on a side of the first electrode110away from the base substrate100, a transparent electrode130and a second electrode141electrically connected with the transparent electrode130on a side of the photoelectric conversion layer120away from the first electrode110. Besides, an orthographic projection of the photoelectric conversion layer120on the base substrate100completely falls within an orthographic projection of the first electrode110on the base substrate100, the photoelectric conversion layer120includes a sidewall121, and an orthographic projection of the sidewall121of the photoelectric conversion layer120is at least partially overlapped with an orthographic projection of the second electrode141on the base substrate100.

For example, as illustrated byFIG. 2B, the orthographic projection of the transparent electrode130on the base substrate100completely falls within the orthographic projection of the photoelectric conversion layer120on the base substrate100, and is not overlapped with the orthographic projection of the sidewall121on the base substrate100. That is to say, in a plane parallel to the base substrate100(i.e., in a plane parallel to X and Y directions), the transparent electrode130is located in a middle portion of the photoelectric conversion layer120, and an orthographic projection of a portion of the photoelectric conversion layer120not covered by the transparent electrode130is at least partially overlapped with the orthographic projection of the second electrode141on the base substrate100, that is, the orthographic projection of the transparent electrode130on the base substrate100is overlapped with a middle portion of the orthographic projection of the photoelectric conversion layer120on the base substrate100, and a portion of the orthographic projection of the photoelectric conversion layer120which is not overlapped with the orthographic projection of the transparent electrode120is at least partially overlapped with the orthographic projection of the second electrode141on the base substrate100.

For example, the sidewall of the photoelectric conversion layer may be perpendicular to the plane where the base substrate is located, the transparent electrode is located in an inner side of the sidewall, and the orthographic projection of the second electrode on the base substrate is overlapped with the orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate, which can compensate a voltage difference generated by a portion of the photoelectric conversion layer not covered by the transparent electrode, thereby reducing the dark-state leakage current generated by the sidewall, and further improving the photoelectric characteristics of the flat panel detector including the detection element.

For example, as illustrated byFIG. 2B, a cross section of the photoelectric conversion layer120taken in a direction perpendicular to the base substrate100has a trapezoid shape (including a standard trapezoid shape and an approximately trapezoid shape, and the approximately trapezoid shape includes a case where a side connecting the two bases is a non-linear line, such as a curved line), a length of the base of the trapezoid shape on a side close to the transparent electrode130is smaller than a length of the base of the trapezoid shape on a side close to the first electrode110, that is, the photoelectric conversion layer120has a inclined sidewall121, and the second electrode141covers at least a part of the inclined sidewall of the photoelectric conversion layer120. The transparent electrode and the second electrode in the present embodiment together serve as a top electrode of the photoelectric conversion layer, and the first electrode serves as a bottom electrode of the photoelectric conversion layer. In the present embodiment, the voltage difference generated by the inclined sidewall of the photoelectric conversion layer can be compensated by adding a part of the top electrode (the second electrode) on the sidewall of the photoelectric conversion layer, thereby reducing the dark-state leakage current generated by the sidewall, and further improving the photoelectric characteristics of the flat panel detector including the detection element.

For example, the photodiode1200in the present embodiment is a PIN type photodiode. The photoelectric conversion layer of the PIN photodiode includes a P layer, an I layer, and an N layer, where the I layer is an intrinsic semiconductor layer or a doped layer of a near-intrinsic semiconductor having a low doping concentration, and the I layer has a relatively large thickness, and occupies almost the entire depletion layer, and therefore most of light passed through the transparent electrode130and incident on the photoelectric conversion layer120is absorbed in the I layer and generates a large number of electron-hole pairs.

For example, as illustrated byFIGS. 2A and 2B, the orthographic projection of the portion of the photoelectric conversion layer120not covered by the transparent electrode130on the base substrate100completely falls within the orthographic projection of the second electrode141on the base substrate100. That is to say, the second electrode141completely covers the inclined sidewall of the photoelectric conversion layer120. In this case, the photoelectric conversion layer120is completely located between the top electrode (the transparent electrode130and the second electrode141together serving as the top electrode of the photoelectric conversion layer120) and the bottom electrode (the first electrode110), which can solve a problem that an electric field of the sidewall of the photoelectric conversion layer is weaker than that of the middle portion of the photoelectric conversion layer to the maximum extent, thereby effectively reducing the generation of leakage current.

For example, a case that the orthographic projection of the portion of the photoelectric conversion layer120not covered by the transparent electrode130on the base substrate100completely falls within the orthographic projection of the second electrode141on the base substrate100includes: in the plane parallel to the base substrate100, the second electrode141is a ring of electrode layer surrounding the transparent electrode130; or, the second electrode141covers both a portion of the photoelectric conversion layer120which has been covered by the transparent electrode130and the inclined sidewall of the photoelectric conversion layer120. In a case where the second electrode141covers the portion of the photoelectric conversion layer120which has been covered by the transparent electrode130, in order to guarantee an illuminated area of the photoelectric conversion layer120(i.e., the illuminated area of the photoelectric conversion layer120serves as an aperture ratio of an imaging unit), the second electrode141is selected as a transparent conductive electrode.

For example, as illustrated byFIGS. 2A and 2B, the second electrode141may just cover the inclined sidewall of the photoelectric conversion layer120.

For example, as illustrated byFIGS. 2A and 2B, a material of the second electrode141in an example of the embodiment of the present disclosure includes a light shielding material, that is, the second electrode141may play a light shielding effect. An ordinary indirect flat panel detector converts X-ray light into visible light by using a scintillation layer, and the converted visible light is relatively divergent. The second electrode in the present embodiment has a certain light shielding effect on the sidewall of the photoelectric conversion layer, such that the irradiation of the divergent light on the sidewall of the photoelectric conversion layer (imaging unit) can be effectively reduced, thereby reducing the influence on the image quality. The detection element provided in the present embodiment is mainly applied to an indirect X-ray flat panel detector.

For example, as illustrated byFIGS. 2A and 2B, the orthographic projection of the portion of the photoelectric conversion layer120not covered by the transparent electrode130on the base substrate100completely falls within the orthographic projection of the second electrode141on the base substrate100, in this case, the second electrode141can have a complete light-shielding effect on the inclined sidewall of the photoelectric conversion layer120, and thus it is possible to further reduce the irradiation of the divergent light on the sidewall of the photoelectric conversion layer (imaging unit).

For example, as illustrated byFIGS. 2A and 2B, the orthographic projection of the transparent electrode130on the base substrate100is not overlapped with the orthographic projection of the second electrode141on the base substrate100, that is, a portion of the photoelectric conversion layer120covered by the transparent electrode130is not overlapped with a portion of the photoelectric conversion layer120covered by the second electrode141, so that it is possible to ensure that the sidewall of the imaging unit (photoelectric conversion layer) can be shielded while not affecting the aperture ratio of the imaging unit.

For example, the detection element includes an imaging region200and a peripheral region210surrounding the imaging region200. The imaging region200is a region of dotted circle inFIG. 2A, i.e., a region where the transparent electrode130is located. The imaging region200is a region where the photoelectric conversion layer120is illuminated. The sidewall of the photoelectric conversion layer120and a region on an outer side of the sidewall are a non-imaged region, i.e., the peripheral region210. The second electrode141is located in the peripheral region210, which does not affect the aperture ratio of the imaging unit, prevents the divergent light from irradiating the sidewall of the photoelectric conversion layer (imaging unit), and may also shield the illumination of external environment light on a side of the second electrode away from the photoelectric conversion layer on the photoelectric conversion layer.

For example, as illustrated byFIGS. 2A and 2B, the detection element provided by the embodiment of the present disclosure further includes: a bias signal line140located on a side of the transparent electrode130away from the photoelectric conversion layer120, the bias signal line140and the transparent electrode130are electrically connected. The bias signal line140is used to provide an external electric field to electrons and holes in the photoelectric conversion layer120. Also, the second electrode141in the embodiment of the present disclosure is electrically connected with the bias signal line140, that is to say, the bias signal line140supplies the second electrode141with the same voltage as the transparent electrode130.

For example, as illustrated byFIGS. 2A and 2B, an orthographic projection of the bias signal line140on the base substrate100is overlapped with a portion of the orthographic projection of the photoelectric conversion layer120on the base substrate100, and an orthographic projection of the portion of the photoelectric conversion layer120not covered by the transparent electrode130and the bias signal line140on the base substrate100completely falls within the orthographic projection of the second electrode141on the base substrate100.

For example, as illustrated byFIGS. 2A and 2B, the detection element provided by the embodiment of the present disclosure further includes: an insulating layer180between the bias signal line140and the transparent electrode130, and the insulating layer180includes a via hole150, and the bias signal line140is electrically connected with the transparent electrode130through the via hole150.

For example, as illustrated byFIG. 2B, the insulating layer180may include a buffer layer105, a resin layer106, and a passivation layer107, the insulating layer180is used for protecting the photoelectric conversion layer120.

For example, as illustrated byFIGS. 2A and 2B, the second electrode141is located on a side of the insulating layer180away from the transparent electrode130.

For example, the second electrode may be located on a side of the bias signal line away from the photoelectric conversion layer, or may be located between the bias signal line and the photoelectric conversion layer.

For example, the second electrode141may be electrically connected with the transparent electrode130through electrical connection with the bias signal line140, and the present embodiment includes but is not limited thereto.

For example, as illustrated byFIGS. 2A and 2B, an example of the present embodiment takes a case where the second electrode141and the bias signal line140are located in the same layer and have the same material as an example, that is, the second electrode141and the bias signal line140are formed through the same patterning process to the same conductive layer, thereby saving processing steps.

For example, the material of the second electrode141and the bias signal line140may include Ag (silver), Al (Aluminum), Mg:Ag (magnesium-silver alloy), Mg:Al (magnesium-aluminum alloy), Au (gold), or other opaque metal materials

For example, as illustrated byFIGS. 2A and 2B, the detection element provided by the embodiment of the present disclosure further includes: a thin film transistor, including a gate electrode102, an active layer103, a source electrode104aand a drain electrode104b. In the present embodiment, a case where the drain electrode104bis used as the first electrode110is described as an example.

For example, the thin film transistor further includes a gate insulating layer101on the gate electrode102.

For example, as illustrated byFIGS. 2A and 2B, the detection element provided by the embodiment of the present disclosure further includes: a gate line170extending in the X direction and a data line160extending in the Y direction. The gate electrode102of the thin film transistor is electrically connected with the gate line170, the gate line170is used to turn on or turn off the thin film transistor, the source electrode104aof the thin film transistor is electrically connected with the data line160, and the drain electrode104bis electrically connected with the photoelectric conversion layer120as the first electrode110. The photoelectric conversion layer120forms an electric field under a bias voltage provided by the bias signal line140, and photoelectrons generated by the photoelectric conversion layer120after being irradiated by light are migrated and accumulated in the first electrode110by an external electric field. After the gate line170turning on the thin film transistor, the electrons accumulated in the first electrode110are read out through the data line160, and converted into a digital signal by a reading chip, and the digital signal is subjected to an image processing at a backend.

For example, as illustrated byFIG. 2B, the detection element provided by the embodiment of the present disclosure further includes a passivation protective layer1080and a resin protective layer108on a side of the bias signal line140away from the photoelectric conversion layer120. The two film layers are used to protect the bias signal line140.

FIG. 3is a partial plan view of a flat panel detector according to another embodiment of the present disclosure. As illustrated byFIG. 3, the flat panel detector provided in the present embodiment includes the detection element provided in any of the above embodiments.

As illustrated byFIG. 3, the flat panel detector includes a plurality of detection elements arranged in an array, that is, the plurality of detection elements are arranged in the X direction and the Y direction.

For example, as illustrated byFIG. 3, the flat panel detector includes a plurality of imaging regions200(a region where the dotted circles are exited) and a peripheral region210surrounding the imaging region200. For example, each of the detection elements includes a second electrode141located in the peripheral region210to cover at least a portion of the inclined sidewall of the photoelectric conversion layer.

For example, the flat panel detector provided in the present embodiment is an indirect flat panel detector.

In the present embodiment, the voltage difference generated by the inclined sidewall of the photoelectric conversion layer can be compensated by adding a part of the top electrode (second electrode) on the sidewall of each photoelectric conversion layer, thereby effectively overcoming the problem of insufficient bias voltage caused by the sidewall of the photoelectric conversion layer having a relatively small slope, thereby improving the photoelectric characteristics of the flat panel detector. In addition, the second electrode in an example of the present embodiment includes a light shielding material, so that it can also effectively reduce the irradiation of the divergent light on the sidewall of the photoelectric conversion layer (imaging unit), so that the influence on the image quality thereof can be reduced.

FIG. 4is a schematic flowchart of a manufacturing method of a detection element according to another embodiment of the present disclosure. As illustrated byFIG. 4, the manufacturing method of the detection element includes: forming a photodiode on a base substrate, and forming the photodiode includes:

S301: forming a first electrode on the base substrate.

For example, before forming the first electrode on the base substrate, the formation of the detection element further includes: forming a thin film transistor on the base substrate. The formation of the thin film transistor includes: sequentially forming a gate electrode, a gate insulating layer, an active layer, a source electrode and a drain electrode. One of the formed source electrode and drain electrode serves as the first electrode of the detection element.

S302: forming a photoelectric conversion layer on a side of the first electrode away from the base substrate.

For example, the formed photoelectric conversion layer is a photoelectric conversion layer of a PIN type photodiode.

S303: forming a transparent electrode and a second electrode electrically connected with the transparent electrode on a side of the photoelectric conversion layer away from the first electrode, wherein an orthographic projection of the photoelectric conversion layer on the base substrate completely falls into an orthographic projection of the first electrode on the base substrate, the photoelectric conversion layer includes a sidewall, and an orthographic projection of the sidewall of the photoelectric conversion layer on the base substrate is at least partially overlapped with the orthographic projection of the second electrode on the base substrate.

For example, the formation of the second electrode includes: forming a second electrode on a side of a portion of the photoelectric conversion layer not covered by the transparent electrode away from the base substrate, such that an orthographic projection of the portion of the photoelectric conversion layer not covered by the transparent electrode completely falls within the orthographic projection of the second electrode on the base substrate.

For example, the orthographic projection of the portion of the photoelectric conversion layer not covered by the transparent electrode on the base substrate is at least partially overlapped with the orthographic projection of the second electrode on the base substrate, that is, the second electrode covers at least a part of the inclined sidewall of the photoelectric conversion layer. The transparent electrode and the second electrode in the present embodiment together serve as a top electrode of the photoelectric conversion layer, and the first electrode serves as a bottom electrode of the photoelectric conversion layer. The voltage difference generated by the inclined sidewall of the photoelectric conversion layer can be compensated by adding a part of the top electrode (second electrode) on the sidewall of the photoelectric conversion layer, thereby reducing the dark-state leakage current generated by the sidewall, and improving the photoelectric characteristics of a flat panel detector including the detection element.

For example, the orthographic projection of the portion of the photoelectric conversion layer not covered by the transparent electrode on the base substrate completely falls within the orthographic projection of the second electrode on the base substrate, that is, the second electrode completely covers the inclined sidewall of the photoelectric conversion layer. In this case, the photoelectric conversion layer is completely located between the top electrode (the transparent electrode and the second electrode together serving as the top electrode of the photoelectric conversion layer) and the bottom electrode (the first electrode), which can solve the problem that an electric field of the sidewall of the photoelectric conversion layer is weaker than that of the middle portion of the photoelectric conversion layer to the maximum extent, thereby effectively reducing the generation of leakage current.

For example, the situation that the orthographic projection of the portion of the photoelectric conversion layer not covered by the transparent electrode on the base substrate completely falls within the orthographic projection of the second electrode on the base substrate includes: in a plane parallel to the base substrate, the second electrode is a ring of electrode layer surrounding the transparent electrode; or, the second electrode covers both a portion of the photoelectric conversion layer which has been covered by the transparent electrode and the inclined sidewall of the photoelectric conversion layer. In a case where the second electrode covers the portion of the photoelectric conversion layer which has been covered by the transparent electrode, in order to guarantee an illuminated area of the photoelectric conversion layer (i.e., the illuminated area of the photoelectric conversion layer as an aperture ratio of an imaging unit), the second electrode is selected as a transparent conductive electrode.

For example, the second electrode may just cover the inclined sidewall of the photoelectric conversion layer.

For example, a material of the second electrode includes a light shielding material, that is to say, the second electrode may have a light shielding effect. Therefore, the second electrode has a certain light-shielding effect on the sidewall of the photoelectric conversion layer, so that the irradiation of the divergent light on the sidewall of the photoelectric conversion layer (imaging unit) can be effectively reduced, so that the influence on the image quality thereof can be reduced.

For example, in a case where the orthographic projection of the portion of the photoelectric conversion layer not covered by the transparent electrode on the base substrate completely falls within the orthographic projection of the second electrode on the base substrate, the second electrode may have a complete light shielding effect on the inclined sidewall of the photoelectric conversion layer, so that the irradiation of the divergent light on the sidewall of the photoelectric conversion layer (imaging unit) can be further reduced.

For example, the orthographic projection of the transparent electrode on the base substrate is not overlapped with the orthographic projection of the second electrode on the base substrate, that is, a portion of the photoelectric conversion layer covered by the transparent electrode is not overlapped with a portion of the photoelectric conversion layer covered by the second electrode, so that it is possible to ensure that the sidewall of the imaging unit (photoelectric conversion layer) can be shielded while not affecting the aperture ratio of the imaging unit.

For example, the manufacturing method of the detection element provided by the present embodiment further includes: forming an insulating layer on a side of the transparent electrode away from the photoelectric conversion layer; patterning the insulating layer to form a via hole; forming a conductive layer on a side of the insulating layer away from the transparent electrode, and the conductive layer being electrically connected with the transparent electrode through the via hole; patterning the conductive layer to form a bias signal line and a second electrode which are electrically connected with each other. The bias signal line is electrically connected with the transparent electrode through the via hole. The second electrode and the bias signal line in the present embodiment are formed by patterning the same conductive layer in the same step, thereby saving process steps. The process is based on the existing process, does not require additional equipment, and is only easy to implement for the shape of the existing film layer (the film layer where the bias signal line is located).

For example, a material of the second electrode and the bias signal line may include an opaque metal material, such as: Ag (silver), Al (aluminum), Mg:Ag (magnesium silver alloy), Mg:Al (magnesium aluminum alloy), Au (gold), and the like.

For example, in the present embodiment, the second electrode and the bias signal line are formed by patterning the same conductive layer in the same step, but the embodiment is not limited to a case that the second electrode and the bias signal line are formed by patterning the same conductive layer in the same step, for example, the bias signal lines and the second electrodes may also be formed in different processes.

For example, the insulating layer may include a buffer layer, a resin layer, and a passivation layer, and the insulating layer is used for protecting the photoelectric conversion layer.

For example, a passivation protective layer and a surface protective resin structure are formed on a side of the bias signal line away from the photoelectric conversion layer to protect the bias signal line.

The following statements should be noted:

(1) Unless otherwise defined, in embodiment(s) and accompanying drawings of the present disclosure, the same reference sign indicates the same meaning.

(2) The drawings accompanying the embodiment(s) of the present disclosure involve only the structure(s) in connection with the embodiment(s) of the present disclosure, and other structure(s) can be referred to common design(s)

(3) For the purpose of clarity only, in accompanying drawings for illustrating the embodiment(s) of the present disclosure, the thickness of a layer or an area may be enlarged. It should understood that, in the case in which a component such as a layer, film, area, substrate or the like is referred to be “on” or “under” another component, it may be directly on or under the another component, or a component may be interposed there-between.

The above are merely specific implementations of the present disclosure without limiting the protection scope of the present disclosure thereto. Within the technical scope revealed in the present disclosure, modification(s) or substitution(s) may be easily conceivable for those skilled who are familiar with the present technical field, and these modification(s) and substitution(s) all should be contained in the protection scope of the present disclosure. Therefore the protection scope of the present disclosure should be based on the protection scope of the appended claims.