Photoelectric conversion layer, preparation method thereof, photovoltaic device and application

Abstract

The invention relates to the technical field of photovoltaics, and provides a photoelectric conversion layer, a preparation method thereof, a photovoltaic device and application. The photoelectric conversion layer comprises at least one Janus MXY two-dimensional material layer, M comprises Mo or W, X comprises S, Se or Te, Y comprises S, Se or Te, and elements of X and Y are different. According to the invention, the vertical polarization characteristic of the Janus MXY two-dimensional material layer is utilized, and an extremely strong spontaneous light current phenomenon is shown, so that the photovoltaic device has ultrahigh light responsiveness and ultrafast light response speed.

Description

Technical Field

[0001] The present application relates to the field of photovoltaic technology, and in particular to a photoelectric conversion layer and a preparation method thereof, a photovoltaic device and applications. Background Art

[0002] In traditional technology, single crystal silicon, polycrystalline silicon and gallium arsenide (GaAs) with three-dimensional crystal structures are used as photovoltaic materials. In order to improve the photoelectric conversion efficiency, it is usually necessary to increase the thickness and area of ​​the photovoltaic material layer, which not only increases the volume of the device, but also limits its application in integrated and miniaturized devices. In addition, in traditional technology, two-dimensional materials such as transition metal chalcogenides are used to form heterojunctions for photodetectors. Although the miniaturization of the device can be achieved, there are still problems such as low output power. Summary of the invention

[0003] Based on this, an embodiment of the present application provides a photoelectric conversion layer with a small volume and high photoelectric conversion efficiency, a preparation method thereof, a photovoltaic device and an application thereof.

[0004] In a first aspect, the present application provides a photoelectric conversion layer, which includes at least one JanusMXY two-dimensional material layer, M includes Mo or W, X includes S, Se or Te, Y includes S, Se or Te, and the elements of X and Y are different.

[0005] In some embodiments, the photoelectric conversion layer includes at least two stacked Janus MXY two-dimensional material layers, and the elements on the contact interface of two adjacent Janus MXY two-dimensional material layers are different.

[0006] Optionally, the angle between two adjacent layers of the Janus MXY two-dimensional material is 0°~360°.

[0007] In some embodiments, the thickness of the photoelectric conversion layer is 0.67 nm to 100 nm.

[0008] In a second aspect, the present application provides a method for preparing a photoelectric conversion layer, the preparation method comprising:

[0009] Provides Surface with MX 2 A substrate for a two-dimensional material layer;

[0010] A metal compound containing Y element is used as a Y source, and the MX 2 The X element on the side of the two-dimensional material layer away from the substrate is replaced by the Y element to prepare a photoelectric conversion layer including a Janus MXY two-dimensional material layer;

[0011] Wherein, M includes Mo or W, X includes S, Se or Te, Y includes S, Se or Te, and X and Y are different elements.

[0012] In some embodiments, the substrate and the MX 2 The two-dimensional material layers are coupled and connected; optionally, the substrate comprises aluminum oxide with a <11-20> crystal orientation.

[0013] In some embodiments, the reaction temperature of the vapor deposition method is greater than or equal to the temperature at which the metal compound containing element Y releases element Y, and the difference between the reaction temperature of the vapor deposition method and the temperature at which the metal compound containing element Y releases element Y is ≤50°C.

[0014] In some embodiments, the Janus MXY two-dimensional material layer is a Janus MoSSe two-dimensional material layer.

[0015] Optionally, the MX 2 The two-dimensional material layer is MoS 2 , the metal compound containing the Y element includes ZnSe.

[0016] Optionally, the MX 2 The two-dimensional material layer is MoSe 2 , the metal compound containing the Y element includes ZnS.

[0017] Optionally, the temperature of the vapor deposition method is 800°C~900°C, the pressure is ≤2torr, and the time is 30min~60min; the atmosphere of the vapor deposition method includes hydrogen and argon, the flow rate of hydrogen is 2sccm~30sccm, and the flow rate of argon is 100sccm~300sccm.

[0018] In a third aspect, the present application provides a photovoltaic device, the photovoltaic device comprising a first conductive layer, a photoelectric conversion layer, and a second conductive layer, the photoelectric conversion layer having a light-facing surface and a light-receiving surface that are oppositely arranged along a thickness direction; the first conductive layer is arranged on the light-facing surface, the second conductive layer is arranged on the light-receiving surface, and the projections of the first conductive layer and the second conductive layer on the photoelectric conversion layer at least partially overlap;

[0019] The photoelectric conversion layer includes the photoelectric conversion layer as described in the first aspect or the photoelectric conversion layer prepared by the preparation method of the photoelectric conversion layer as described in the second aspect.

[0020] In some embodiments, the material of the first conductive layer includes at least one of graphene and a transparent conductive material.

[0021] In some embodiments, the material of the second conductive layer includes at least one of graphene, a metal conductive material, and a transparent conductive glass.

[0022] In some embodiments, the thickness of the first conductive layer is 0.34 nm to 10 nm.

[0023] In some embodiments, the thickness of the second conductive layer is 0.34 nm to 1 μm.

[0024] In some embodiments, the transmittance of the first conductive layer is ≥10%.

[0025] In some embodiments, the photovoltaic device further comprises a first encapsulation layer and a second encapsulation layer, wherein the first encapsulation layer is disposed on a side of the first conductive layer away from the photoelectric conversion layer; and the second encapsulation layer is disposed on a side of the second conductive layer away from the photoelectric conversion layer.

[0026] Optionally, the material of the first encapsulation layer includes boron nitride.

[0027] Optionally, a material of the second encapsulation layer includes at least one of boron nitride and silicon oxide.

[0028] Optionally, the first encapsulation layer has a thickness of 1 nm to 100 nm.

[0029] Optionally, the second encapsulation layer has a thickness of 1 nm to 1 μm.

[0030] In a fourth aspect, the present application provides an application of the photovoltaic device as described in the third aspect, wherein the photovoltaic device is used to prepare a solar cell, a photodetector or a photoelectric chip.

[0031] Compared with the traditional technology, this application has at least the following beneficial effects:

[0032] In the Janus MXY two-dimensional material layer of the present application, the two sides of the M element are the X element and the Y element, respectively, and the X element and the Y element are arranged in an orderly manner on both sides of the M element, so that the Janus MXY two-dimensional material layer has a vertical polarization characteristic and exhibits a very strong self-luminous current phenomenon. 2 or MoSe 2 Compared with two-dimensional materials such as Janus MXY, etc., the photoelectric conversion layer of the present application not only has a single-layer Janus MXY two-dimensional material layer that can output a higher photocurrent, but also the multi-layer structure does not require interlayer angle regulation and heterojunction formation.

[0033] The spontaneous polarization of the photoelectric conversion layer in the photoelectric device of the present application triggers the accumulation of surface charges. The free electrons in the conductive layer shield these surface charges to form dipoles in the same direction, thereby generating an electric potential at the interface between the conductive layer and the photoelectric conversion layer. Since the induced charge cannot completely compensate for the charge in the Janus MXY two-dimensional material layer, the depolarization field formed drives the separation of electron-hole pairs, and eventually the electron-hole pairs can be collected by the electrode through interfacial charge transfer, thereby forming a photocurrent. The photovoltaic device of the present application has ultra-high photoresponsivity and ultra-fast photoresponse speed. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 A schematic structural diagram of a photovoltaic device provided in one embodiment of the present application; wherein, 100 - photoelectric conversion layer; 200 - first conductive layer; 300 - second conductive layer; 400 - first encapsulation layer; 500 - second encapsulation layer; 600 - substrate.

[0035] Figure 2 This is a perspective view of the photovoltaic device prepared in Example 1 of the present application.

[0036] Figure 3 This is the photocurrent response diagram of the photovoltaic device prepared in Example 1 of the present application.

[0037] Figure 4 This is the ultrafast photocurrent response diagram of the photovoltaic device prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0038] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are described in detail below. In the following description, many specific details are set forth to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar improvements without violating the connotation of the present application, so the present application is not limited by the specific embodiments disclosed below.

[0039] In the description of the present application, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the referred device or element must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0040] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "plurality" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined.

[0041] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0042] In the present application, unless otherwise clearly specified and limited, a first feature being “above” or “below” a second feature may mean that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, a first feature being “above”, “above”, and “above” a second feature may mean that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is higher in level than the second feature. A first feature being “below”, “below”, and “below” a second feature may mean that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is lower in level than the second feature.

[0043] It should be noted that when an element is referred to as being "fixed to" or "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "upper", "lower", "left", "right" and similar expressions used herein are for illustrative purposes only and are not intended to be the only implementation method.

[0044] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application belongs. The terms used herein in the specification of this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0045] In traditional technology, single crystal silicon, polycrystalline silicon and gallium arsenide (GaAs) photovoltaic materials are integrated with photovoltaic modules to improve the photoelectric conversion efficiency and promote the large-scale application of solar power generation. However, due to the physical properties of the materials, traditional photovoltaic devices usually have the problems of large size and weight. In addition, the production process of traditional photovoltaic devices is complex and energy-intensive, resulting in high manufacturing costs. Furthermore, two-dimensional van der Waals materials (such as MoS 2 or MoSe 2 The unique atomic-level thickness, surface without dangling bonds and high optical nonlinear effect of 2D materials have shown excellent performance potential in the field of micro-nano integration and can be combined with various optical microcavities to achieve higher photoelectric conversion efficiency. However, the current optoelectronic devices based on 2D materials still have technical problems such as thick thickness, complex structure and low photoelectric conversion efficiency, which hinder their large-scale practical application.

[0046] Based on this, the first aspect of the present application provides a photoelectric conversion layer, which includes at least one Janus MXY two-dimensional material layer, M includes Mo or W, X includes S, Se or Te, Y includes S, Se or Te, and the elements of X and Y are different.

[0047] In the Janus MXY two-dimensional material layer of the present application, the two sides of the M element are the X element and the Y element, respectively, and the X element and the Y element are arranged in an orderly manner on both sides of the M element, so that the Janus MXY two-dimensional material layer has a vertical polarization characteristic and exhibits a very strong self-luminous current phenomenon. 2 or MoSe 2 Compared with two-dimensional materials such as Janus MXY, etc., the photoelectric conversion layer of the present application not only has a single-layer Janus MXY two-dimensional material layer that can output a higher photocurrent, but also the multi-layer structure does not require interlayer angle regulation and heterojunction formation.

[0048] It should be noted that Janus MXY two-dimensional materials refer to materials formed by breaking the out-of-plane symmetry of the structure of traditional two-dimensional transition metal chalcogenides. That is to say, in the Janus MXY two-dimensional material in this application, the M element is located in the center, the X elements are all on the same side of the M element, and the Y elements are all on the side of the M element opposite to the X element, forming an XMY sandwich structure. 2 For example, it is a symmetrical structure of S-Mo-S, then Janus-type MoSSe is MoS 2 All the S atoms in one of the two-dimensional material layers are replaced by Se atoms, thus forming a S-Mo-Se sandwich structure.

[0049] In some embodiments, the photoelectric conversion layer includes at least two layers of the Janus MXY two-dimensional material layer stacked, and the elements on the contact interface of the two adjacent layers of the Janus MXY two-dimensional material layer are different. That is to say, the multiple layers of Janus MXY two-dimensional material layers are stacked in an XMY manner or a YMX manner along the stacking direction. For example, the photoelectric conversion layer includes a first Janus MXY two-dimensional material layer and a second Janus MXY two-dimensional material layer stacked in sequence, if the first Janus MXY two-dimensional material layer is close to the second Janus MXY two-dimensional material layer. The side of the second Janus MXY two-dimensional material layer close to the first Janus MXY two-dimensional material layer is the Y element.

[0050] The present application selects a stacking method of multiple layers of Janus MXY two-dimensional material layers as above, so that the surface charge polarity of the Janus MXY two-dimensional material layers is the same during the spontaneous photovoltaic effect, effectively enhancing the spontaneous photovoltaic effect. If the elements at the contact interface of two adjacent layers of Janus MXY two-dimensional material layers are the same, the charges caused by spontaneous polarization may cancel each other at the contact interface, and no photocurrent can be generated.

[0051] Optionally, the angle between two adjacent Janus MXY two-dimensional material layers is 0° to 360°. In the present application, the stacking angle of the Janus MXY two-dimensional material layers does not need to be adjusted, and efficient output of photocurrent can be achieved at any angle.

[0052] In some embodiments, the thickness of the photoelectric conversion layer is 0.67 nm to 100 nm. The thickness of the photoelectric conversion layer is selected as above in the present application to effectively increase the photoelectric current. Since the intensity of the depolarization field that produces the photovoltaic effect is inversely proportional to the thickness of the photoelectric conversion layer, if the thickness of the photoelectric conversion layer is relatively large, the intensity of the depolarization field may be reduced, and there may also be problems such as insufficient light penetration depth and increased defects in the photoelectric conversion layer.

[0053] A second aspect of the present application provides a method for preparing a photoelectric conversion layer, the preparation method comprising:

[0054] Provides Surface with MX 2 A substrate for a two-dimensional material layer;

[0055] A metal compound containing Y element is used as a Y source, and the MX 2 The X element on the side of the two-dimensional material layer away from the substrate is replaced by the Y element to prepare a photoelectric conversion layer including a Janus MXY two-dimensional material layer;

[0056] Wherein, M includes Mo or W, X includes S, Se or Te, Y includes S, Se or Te, and X and Y are different elements.

[0057] The present invention adopts a metal compound containing Y element as a Y source, which has the characteristics of good release uniformity and high activity, and can thus release MX on the substrate. 2 The X element on the side of the two-dimensional material layer away from the substrate is completely replaced, effectively avoiding the problem of uneven replacement, and the formed Janus MXY two-dimensional material layer has fewer impurities and fewer defects. In the Janus MXY two-dimensional material layer prepared by the present application, the two sides of the M element are the X element and the Y element, respectively, and the X element and the Y element are arranged in an orderly manner on both sides of the M element, so that the Janus MXY two-dimensional material layer has a vertical polarization characteristic and exhibits a very strong self-luminous current phenomenon. Compared with traditional transition metal chalcogenides (such as MoS 2 or MoSe 2 Compared with two-dimensional materials such as JanusMXY, etc., the photoelectric conversion layer of the present application can not only output a higher photocurrent than a single-layer JanusMXY two-dimensional material layer, but also the multi-layer structure does not require interlayer angle regulation and heterojunction formation.

[0058] It can be understood that the photoelectric conversion layer may include multiple layers of Janus MXY two-dimensional material layers, and the multiple layers of Janus MXY two-dimensional material layers may be stacked by transfer.

[0059] In some embodiments, the substrate and the MX 2 The two-dimensional material layer is coupled and connected. It can be understood that the substrate and MX 2 The coupling connection between the two-dimensional material layer refers to the substrate and MX 2 The two-dimensional material layers are tightly combined, and it is difficult for the Y element to react with the MX during the preparation process. 2 The X element on the side of the two-dimensional material layer close to the substrate is substituted.

[0060] Optionally, the substrate comprises aluminum oxide with a <11-20> crystal orientation.

[0061] The present application selects a substrate as above, and the substrate and MX 2 The material has strong coupling and close combination, so it is easy to replace MX in the process of vapor deposition. 2 The X element on the side of the material far from the substrate is replaced, while the X element on the side close to the substrate is not easily replaced, which further improves the purity and uniformity of the prepared Janus MXY two-dimensional material layer and can reduce material defects.

[0062] In some embodiments, the reaction temperature of the vapor deposition method is greater than or equal to the temperature at which the metal compound containing the Y element releases the Y element, and the difference between the reaction temperature of the vapor deposition method and the temperature at which the metal compound containing the Y element releases the Y element is ≤50° C. The temperature at which the Y source selected in the present application releases the Y element is close to the reaction temperature, which further improves the dispersion uniformity and reduces the defects of the Janus MXY two-dimensional material layer.

[0063] In some embodiments, the Janus MXY two-dimensional material layer is a Janus MoSSe two-dimensional material layer.

[0064] Optionally, the MX 2 The two-dimensional material layer is MoS 2 The metal compound containing the Y element includes ZnSe. The temperature at which the Se element in ZnSe is released is 750°C to 880°C.

[0065] Optionally, the temperature of the vapor deposition method is 800°C to 900°C, for example, it can be 800°C, 810°C, 820°C, 830°C, 840°C, 850°C, 860°C, 870°C, 880°C, 890°C or 900°C.

[0066] Optionally, the pressure of the vapor deposition method is ≤2 torr.

[0067] Optionally, the vapor deposition method takes 30 min to 60 min.

[0068] Optionally, the atmosphere of the vapor deposition method includes hydrogen and argon, the flow rate of the hydrogen is 2 sccm~30 sccm, and the flow rate of the argon is 100 sccm~300 sccm.

[0069] Optionally, the MX 2 The two-dimensional material layer is MoSe 2 , the metal compound containing the Y element includes ZnS.

[0070] It is understandable that different MX 2 Different Y sources are selected for the two-dimensional material layer so that the temperature at which the Y source releases the Y element is close to the reaction temperature, thereby improving the dispersion uniformity of the Y element during the reaction process and reducing the defects of the Janus MXY two-dimensional material layer.

[0071] Exemplarily, a method for preparing the above-mentioned photoelectric conversion layer is provided, comprising the following steps:

[0072] Provides Surface with MX 2 A substrate for a two-dimensional material layer;

[0073] A metal compound containing Y element is used as a Y source, and the MX 2 The X element on the side of the two-dimensional material layer away from the substrate is replaced by the Y element to prepare a photoelectric conversion layer including a Janus MXY two-dimensional material layer;

[0074] Furthermore, a plurality of Janus MXY two-dimensional material layers are prepared and transferred and stacked to form a photoelectric conversion layer stacked with multiple Janus MXY two-dimensional material layers.

[0075] In a third aspect, the present application provides a photovoltaic device, the photovoltaic device comprising a first conductive layer, a photoelectric conversion layer, and a second conductive layer, the photoelectric conversion layer having a light-facing surface and a light-receiving surface that are oppositely arranged along a thickness direction; the first conductive layer is arranged on the light-facing surface, the second conductive layer is arranged on the light-receiving surface, and the projections of the first conductive layer and the second conductive layer on the photoelectric conversion layer at least partially overlap;

[0076] The photoelectric conversion layer includes the photoelectric conversion layer as described in the first aspect or the photoelectric conversion layer prepared by the preparation method of the photoelectric conversion layer as described in the second aspect.

[0077] The spontaneous polarization of the photoelectric conversion layer in the photoelectric device of the present application triggers the accumulation of surface charges. The free electrons in the conductive layer shield these surface charges to form dipoles in the same direction, thereby generating an electric potential at the interface between the conductive layer and the photoelectric conversion layer. Since the induced charge cannot completely compensate for the charge in the Janus MXY two-dimensional material layer, the depolarization field formed drives the separation of electron-hole pairs, and eventually the electron-hole pairs can be collected by the electrode through interfacial charge transfer, thereby forming a photocurrent. The photovoltaic device of the present application has ultra-high photoresponsivity and ultra-fast photoresponse speed.

[0078] In some embodiments, the projections of the first conductive layer and the second conductive layer on the photoelectric conversion layer completely overlap. The present application has found that the photoelectric effect of the non-overlapping portion of the projections of the first conductive layer and the second conductive layer is very weak and can be ignored compared to the photoelectric effect of the overlapping portion of the projections.

[0079] It can be understood that the function of the first conductive layer and the second conductive layer in the present application is to conduct the current formed in the photoelectric conversion layer.

[0080] In some embodiments, the material of the first conductive layer includes graphene and a transparent conductive material, wherein the transparent conductive material may be transparent conductive glass or the like.

[0081] In some embodiments, a material of the second conductive layer includes at least one of graphene, a metal conductive material, and a transparent conductive material.

[0082] It is understood that the first conductive layer and the second conductive layer can cover the photoelectric conversion layer and can achieve current conduction. In some embodiments, the thickness of the first conductive layer is 0.34nm~100nm. In some embodiments, the thickness of the second conductive layer is 0.34nm~1μm.

[0083] In some embodiments, the transmittance of the first conductive layer is ≥ 10%.

[0084] In some embodiments, the photovoltaic device further includes a first encapsulation layer and a second encapsulation layer, wherein the first encapsulation layer is disposed on a side of the first conductive layer away from the photoelectric conversion layer; and the second encapsulation layer is disposed on a side of the second conductive layer away from the photoelectric conversion layer.

[0085] Optionally, the material of the first encapsulation layer includes boron nitride.

[0086] Optionally, a material of the second encapsulation layer includes at least one of boron nitride and silicon oxide.

[0087] Optionally, the first encapsulation layer has a thickness of 1 nm to 100 nm.

[0088] Optionally, the second encapsulation layer has a thickness of 1 nm to 1 μm.

[0089] In some embodiments, the photovoltaic device further includes a first electrode and a second electrode, the first electrode is connected to the first conductive layer, the second electrode is connected to the second conductive layer, and the first electrode and the second electrode are used to achieve electronic conduction of the photovoltaic device.

[0090] In some embodiments, the photovoltaic device further includes a substrate, which is disposed on a side of the second encapsulation layer away from the photoelectric conversion layer, and is used to provide support for the photovoltaic device.

[0091] like Figure 1 As shown, the photovoltaic device includes a substrate 600, a second encapsulation layer 500, a second conductive layer 300, a photoelectric conversion layer 100, a first conductive layer 200 and a first encapsulation layer 400 which are stacked in sequence.

[0092] It is understandable that the first encapsulation layer, the first conductive layer, the photoelectric conversion layer, the second conductive layer and the second encapsulation layer may be stacked and assembled in this order by means of transfer.

[0093] A fourth aspect of the present application provides an application of the photovoltaic device as described in the third aspect, wherein the photovoltaic device is used to prepare a solar cell, a photodetector or a photoelectric chip.

[0094] The embodiments of the present application will be described in detail below in conjunction with examples. It should be understood that these examples are only used to illustrate the present application and are not intended to limit the scope of the present application. The experimental methods for which specific conditions are not specified in the following examples are preferably referred to the guidance provided in the present application, and can also be based on the experimental manual or normal conditions in this area, can also be based on the conditions recommended by the manufacturer, or refer to experimental methods known in the art.

[0095] Example 1

[0096] (1) Preparation of Janus MoSSe two-dimensional material layer

[0097] Providing a surface with MoS 2 The substrate is aluminum oxide with a crystal orientation of <11-20>;

[0098] MoS was grown at 870℃ for 30min using ZnSe as Se source and 120sccm argon and 5sccm hydrogen at a pressure of 1torr. 2 Se-type MoS 2 The S element on the side away from the substrate is substituted to prepare a Janus MoSSe two-dimensional material layer with a thickness of 0.67nm.

[0099] (2) Assembling photovoltaic devices

[0100] Using PPC (polymethyl ethylene carbonate) and PMMA (polymethyl methacrylate), transfer lamination is performed in the order of a first encapsulation layer, a first conductive layer, a photoelectric conversion layer, a second conductive layer, and a second encapsulation layer, and the projections of the first conductive layer and the second conductive layer on the photoelectric conversion layer completely overlap. The photoelectric conversion layer is a Janus MoSSe two-dimensional material layer prepared in the above step (1); the first encapsulation layer and the second encapsulation layer are boron nitride with a thickness of 10 nm; the first conductive layer and the second conductive layer are graphene with a thickness of 1 nm. Then, gold electrodes are respectively arranged on the first conductive layer and the second conductive layer to assemble the photovoltaic device.

[0101] Example 2

[0102] The Janus MoSSe two-dimensional material layer is prepared and the photovoltaic device is assembled according to the method of Example 1, except that the photoelectric conversion layer includes two stacked Janus MoSSe two-dimensional material layers, wherein the Janus MoSSe two-dimensional material layers are arranged in the order of S-Mo-Se along the stacking direction.

[0103] Example 3

[0104] The Janus MoSSe two-dimensional material layer was prepared and the photovoltaic device was assembled according to the method of Example 1, except that the second conductive layer was replaced by ITO with a thickness of 50 nm.

[0105] Comparative Example 1

[0106] The Janus MoSSe two-dimensional material layer is prepared and the photovoltaic device is assembled according to the method of Example 1, the difference being that there is no overlapping part between the projections of the first conductive layer and the second conductive layer on the photoelectric conversion layer, and only the first conductive layer or the second conductive layer overlaps with the photoelectric conversion layer.

[0107] Comparative Example 2

[0108] The photovoltaic device is assembled according to the method of Example 1, except that the photoelectric conversion layer is replaced by the first MoS 2 2D material layers and the second MoS 2 Two-dimensional material layer, first MoS 2 2D material layers and the second MoS 2 The interlayer rotation angle of the two-dimensional material layer is 60 degrees, and the interlayer rotation angle refers to the angle between two layers of MoS 2 The corner between crystal phases.

[0109] Comparative Example 3

[0110] The photovoltaic device is assembled according to the method of Example 2, except that a layer of graphene with a thickness of 1 nm is added between the Janus MoSSe two-dimensional material layers on both sides to form a photoelectric conversion layer.

[0111] The photovoltaic device prepared as above was subjected to performance testing, and the testing method included: testing the photocurrent intensity of the photovoltaic device at zero bias under illumination (633 nm, 100 μW). The test results are shown in Table 1.

[0112] Table 1

[0113]

[0114] From the above table we can see that:

[0115] (1) Compared with Example 3, it can be seen that the materials such as graphene and ITO used in this application are only used as conductive layers, that is, the conductive layers only need to have a conductive function. Compared with ITO materials, graphene has an atomically flat surface and fewer surface defects, thus having a better photovoltaic effect.

[0116] (2) Through Example 1 and Comparative Examples 1-2, combined with Figure 3 It can be seen that under light (633nm), the photovoltaic device of the present application exhibits a significant self-luminous current, while MoS 2The device does not have a similar phenomenon. By scanning the photocurrent, it is found that the spontaneous photovoltaic effect only occurs in the stacked area of ​​the first conductive layer, the photoelectric conversion layer and the second conductive layer. The photocurrent in the stacked area with only the photoelectric conversion layer and the first conductive layer, and the photocurrent in the stacked area with only the photoelectric conversion layer and the second conductive layer is negligible, eliminating the influence of the thermal effect or pn junction effect caused by laser radiation. Moreover, by comparing Example 1 with Example 2, the spontaneous photovoltaic effect of the photoelectric conversion layer of the present application is significantly enhanced as the number of layers increases.

[0117] Furthermore, if Figure 4 As shown, the present application adopts ultrafast time-resolved photocurrent autocorrelation spectroscopy technology. By applying 0.5mW continuous laser pulses with time delay, it is found that when the two pulses overlap, the photocurrent reaches a minimum value, reflecting the saturation effect under high power; and when the time delay is not zero, the photocurrent gradually increases. The rising part of the photocurrent curve reveals the resolution ability of the photovoltaic device for continuous pulses. The exponential fitting of the rising curve shows that the typical response time of the photovoltaic device in Example 1 is about 50ps, the bandwidth is 11GHz, and it is not affected by the pump power.

[0118] Therefore, in the Janus MXY two-dimensional material layer of the present application, the two sides of the M element are the X element and the Y element, respectively, and the X element and the Y element are arranged in an orderly manner on both sides of the M element, so that the Janus MXY two-dimensional material layer has a vertical polarization characteristic and exhibits a very strong self-luminous current phenomenon. 2 or MoSe 2 Compared with two-dimensional materials such as Janus MXY, etc., the photoelectric conversion layer of the present application not only has a single-layer Janus MXY two-dimensional material layer that can output a higher photocurrent, but also the multi-layer structure does not require interlayer angle regulation and heterojunction formation.

[0119] (3) Compared with Comparative Example 3, in Example 2, graphene is inserted into the photoelectric conversion layer. Although a heterojunction structure is formed between the Janus MXY two-dimensional material layer and the graphene, the presence of graphene enhances the spontaneous polarization shielding effect of the photoelectric conversion layer and weakens the depolarization field. At the same time, graphene also produces additional light absorption, thereby affecting the photoelectric conversion effect.

[0120] Therefore, the spontaneous polarization of the photoelectric conversion layer in the photoelectric device of the present application triggers the accumulation of surface charges, and the free electrons in the conductive layer shield these surface charges to form dipoles with the same direction, thereby generating an electric potential at the interface between the conductive layer and the photoelectric conversion layer. Since the induced charge cannot completely compensate for the charge in the Janus MXY two-dimensional material layer, the depolarization field formed drives the separation of electron-hole pairs, and eventually the electron-hole pairs can be collected by the electrode through interfacial charge transfer, thereby forming a photocurrent. The photovoltaic device of the present application has ultra-high photoresponsivity and ultra-fast photoresponse speed.

[0121] In summary, the present application integrates a photoelectric conversion layer containing a Janus MXY two-dimensional material layer with a photovoltaic device. The unique asymmetric lattice structure and inherent vertical polarization of the Janus MXY two-dimensional material are utilized, and the photoelectric performance is optimized by adjusting its atomic composition and thickness, thereby greatly improving the conversion efficiency of the spontaneous photovoltaic effect.

[0122] The structure of the photoelectric conversion layer of the present application has significant advantages in generating photocurrent, and can achieve efficient photoelectric conversion and electron-hole pair separation, and achieve more precise optimization of photovoltaic performance. Compared with traditional photovoltaic materials, the photoelectric conversion layer of the present application not only improves the conversion efficiency, but also achieves high-efficiency self-luminous current output, providing a new direction for the design of miniaturized and high-efficiency photovoltaic devices.

[0123] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be construed as limiting the scope of the application. It should be noted that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A photoelectric conversion layer, characterized in that: The photoelectric conversion layer includes at least one Janus MXY two-dimensional material layer, M includes Mo or W, X includes S, Se or Te, Y includes S, Se or Te, and X and Y are different elements.

2. The photoelectric conversion layer according to claim 1, wherein The photoelectric conversion layer comprises at least two layers of the Janus MXY two-dimensional material layer stacked, and the elements on the contact interface of two adjacent layers of the Janus MXY two-dimensional material layer are different; Optionally, the angle between two adjacent layers of the Janus MXY two-dimensional material is 0°~360°.

3. The photoelectric conversion layer according to claim 1 or 2, characterized in that The thickness of the photoelectric conversion layer is 0.67nm~100nm.

4. A method for preparing a photoelectric conversion layer, characterized in that: The preparation method comprises: Providing a substrate having a MX2 two-dimensional material layer on the surface; Using a metal compound containing the Y element as a Y source, and using a vapor deposition method to replace the X element on the side of the MX2 two-dimensional material layer away from the substrate with the Y element, so as to prepare a photoelectric conversion layer including a Janus MXY two-dimensional material layer; Wherein, M includes Mo or W, X includes S, Se or Te, Y includes S, Se or Te, and X and Y are different elements.

5. The preparation method according to claim 4, characterized in that: The preparation method satisfies at least one of the following conditions: (1) The substrate is coupled to the MX2 two-dimensional material layer; optionally, the substrate comprises aluminum oxide with a <11-20> crystal orientation; (2) The reaction temperature of the vapor deposition method is greater than or equal to the temperature at which the metal compound containing the element Y releases the element Y, and the difference between the reaction temperature of the vapor deposition method and the temperature at which the metal compound containing the element Y releases the element Y is ≤50°C.

6. The preparation method according to claim 4 or 5, characterized in that: The Janus MXY two-dimensional material layer is a JanusMoSSe two-dimensional material layer, and the preparation method satisfies at least one of the following conditions: (1) The MX2 two-dimensional material layer is MoS2, and the metal compound containing the Y element includes ZnSe; (2) The MX2 two-dimensional material layer is MoSe2, and the metal compound containing the Y element includes ZnS; (3) The temperature of the vapor deposition method is 800°C~900°C, the pressure is ≤2torr, and the time is 30min~60min; the atmosphere of the vapor deposition method includes hydrogen and argon, the flow rate of the hydrogen is 2sccm~30sccm, and the flow rate of the argon is 100sccm~300sccm.

7. A photovoltaic device, characterized in that: The photovoltaic device comprises a first conductive layer, a photoelectric conversion layer and a second conductive layer which are stacked, wherein the photoelectric conversion layer has a light-facing surface and a light-receiving surface which are oppositely arranged along the thickness direction; the first conductive layer is arranged on the light-facing surface, the second conductive layer is arranged on the light-receiving surface, and the projections of the first conductive layer and the second conductive layer on the photoelectric conversion layer at least partially overlap; The photoelectric conversion layer comprises the photoelectric conversion layer according to any one of claims 1 to 3 or a photoelectric conversion layer prepared by the method for preparing a photoelectric conversion layer according to any one of claims 4 to 6.

8. The photovoltaic device according to claim 7, characterized in that: The photovoltaic device satisfies at least one of the following conditions: (1) The material of the first conductive layer includes at least one of graphene and a transparent conductive material; (2) The material of the second conductive layer includes at least one of graphene, metal conductive material and transparent conductive glass; (3) The thickness of the first conductive layer is 0.34 nm to 100 nm; (4) The thickness of the second conductive layer is 0.34 nm to 1 μm; (5) The light transmittance of the first conductive layer is ≥10%.

9. The photovoltaic device according to claim 7 or 8, characterized in that: The photovoltaic device further comprises a first encapsulation layer and a second encapsulation layer, wherein the first encapsulation layer is arranged on a side of the first conductive layer away from the photoelectric conversion layer; and the second encapsulation layer is arranged on a side of the second conductive layer away from the photoelectric conversion layer. Optionally, the material of the first encapsulation layer includes boron nitride; Optionally, the material of the second encapsulation layer includes at least one of boron nitride and silicon oxide; Optionally, the thickness of the first encapsulation layer is 1 nm to 100 nm; Optionally, the second encapsulation layer has a thickness of 1 nm to 1 μm.

10. An application of the photovoltaic device according to any one of claims 7 to 9, characterized in that: The photovoltaic device is used for preparing solar cells, photoelectric detectors or photoelectric chips.

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