Semitransparent ultrathin CIGS thin film solar cell and preparation method thereof

Abstract

The invention provides a semitransparent ultrathin copper-indium-gallium-selenium thin film solar cell and a preparation method thereof. The thin film solar cell comprises a substrate, a light absorption layer, an interface modification layer, a buffer layer, a window layer and a gate electrode. Wherein the substrate is made of a transparent conductive material; the light absorption layer is copper indium gallium selenium, is formed above the substrate, and is suitable for absorbing sunlight and generating current carriers; the interface modification layer is formed between the substrate and the light absorption layer and is suitable for providing a crystallization plane of the light absorption layer, passivating a contact surface of the substrate and the light absorption layer, preventing element diffusion of the light absorption layer and reducing carrier recombination of the contact surface; the buffer layer is formed on the light absorption layer and is suitable for forming a potential barrier and adjusting a work function so as to transmit current carriers and form light current; the window layer is formed on the buffer layer and is suitable for allowing sunlight to enter, providing forward bias voltage and preventing current carriers from flowing reversely; a gate electrode is formed over the window layer, suitable for collecting and transmitting photocurrent.

Description

Technical Field

[0001] The present disclosure relates to the technical field of thin-film solar cells, and in particular to a semi-transparent ultra-thin copper indium gallium selenide thin-film solar cell and a preparation method thereof. Background Art

[0002] Copper indium gallium selenide (CIGS) thin film solar cells are thin film photovoltaic devices that use the semiconductor layer of copper indium gallium selenide (CIGS) to absorb sunlight and convert it into electrical energy. Copper indium gallium selenide (CIGS) thin film solar cells have the characteristics of high conversion efficiency, good weak light characteristics, stable performance, flexibility, etc., and have broad market prospects. Traditional CIGS cells use metal molybdenum (Mo) as a substrate, and the absorption layer thickness is 1.5-2μm. The efficiency of CIGS cell devices has reached 23.6%, and the module efficiency exceeds 19%. However, traditional Mo substrate GIGS cells have certain disadvantages in terms of material limitations, preparation process complexity, performance limitations and environmental impact. In order to overcome these disadvantages, it is currently a hot topic to continuously explore new substrate materials, optimize preparation processes, improve battery performance, and strengthen the recycling and treatment of waste batteries.

[0003] Semi-transparent ultra-thin CIGS cells can achieve visible light transmission in cell devices by reducing the thickness of the absorption layer and using transparent conductive oxide (TCO) instead of the traditional Mo substrate. This not only shortens the deposition time in the preparation process, greatly reduces the material consumption of rare elements indium and gallium, and reduces production costs; its double-sidedness and semi-transparent characteristics further expand the application market, such as top cells of tandem cells and building integrated photovoltaics (BIPV).

[0004] TCO thin films have two major characteristics: transparency and conductivity. They are the basis for the manufacture of many transparent electronic components. However, the semi-transparent ultra-thin CIGS cells using them still have the following problems:

[0005] 1) In order to obtain good crystal quality, the co-evaporation deposition temperature of the light absorption layer of CIGS cells is usually higher than 550°C, which is far higher than the heat resistance temperature of TCO materials, resulting in significant degradation of the photoelectric performance of the back electrode; while lowering the deposition temperature will cause the crystal quality of the CIGS light absorption layer to decrease, the grain size to shrink, and the body recombination in the device to intensify;

[0006] 2) The work functions of the TCO material and the CIGS light absorption layer do not match, and direct contact will form a Schottky barrier, hindering hole transmission; during the high-temperature preparation process of the light absorption layer, an amorphous, high-resistance GaOx layer may be generated between the TCO and CIGS light absorption layers, seriously affecting device performance;

[0007] 3) The traditional CIGS cell structure forms a conduction band gradient through In / Ga diffusion to separate carriers. After the thickness of the absorption layer is reduced, the element diffusion is more uniform, and it is difficult to form a steep back gradient, resulting in serious carrier recombination at the interface of the TCO / CIGS light absorption layer.

[0008] Therefore, it is of far-reaching practical significance to prepare a semi-transparent ultra-thin CIGS cell with a more stable and reliable structure to improve the quality and efficiency of CIGS thin-film solar cells. Summary of the invention

[0009] In view of this, in order to at least partially solve at least one of the above-mentioned technical problems, the present disclosure proposes a semi-transparent ultra-thin copper indium gallium selenide thin-film solar cell, including a substrate, a light absorption layer, an interface modification layer, a buffer layer, a window layer and a gate electrode. Among them, the substrate is made of a transparent conductive material; the light absorption layer is formed on the top of the substrate, and the material of the light absorption layer is copper indium gallium selenide, which is suitable for absorbing sunlight and generating carriers; the interface modification layer is formed between the substrate and the light absorption layer, which is suitable for providing a crystal plane of the light absorption layer, and passivating the contact surface between the substrate and the light absorption layer, preventing the element diffusion of the light absorption layer, and reducing the carrier recombination at the contact surface; the buffer layer is formed on the light absorption layer, which is suitable for forming a potential barrier and adjusting the work function to transmit carriers and form a photocurrent; the window layer is formed on the buffer layer, which is suitable for allowing sunlight to enter and providing a forward bias to prevent the reverse flow of carriers; the gate electrode is formed on the window layer, which is suitable for collecting and transmitting photocurrent.

[0010] According to an embodiment of the present disclosure, the thickness of the interface modification layer is 5-50 nm, the thickness of the light absorption layer is 200-700 nm, the thickness of the buffer layer is 20-80 nm, and the thickness of the window layer is 220-400 nm.

[0011] According to an embodiment of the present disclosure, the transparent conductive material includes at least one of indium tin oxide, fluorine-doped tin oxide, titanium-doped indium oxide, and gallium-doped zinc oxide; the material of the interface modification layer is molybdenum oxide; the material of the buffer layer includes at least one of cadmium sulfide, zinc oxysulfide, zinc magnesium oxide, zinc tin oxide, and indium sulfide; the materials of the window layer are intrinsic zinc oxide and aluminum-doped zinc oxide; and the materials of the gate electrode include nickel and aluminum.

[0012] According to an embodiment of the present disclosure, the band gap width of molybdenum oxide is 2.80-3.40 eV.

[0013] In another aspect of the present disclosure, a method for preparing the aforementioned thin-film solar cell is also proposed, comprising:

[0014] Depositing molybdenum on a substrate made of a transparent conductive material to obtain a metal layer, and oxidizing the metal layer to obtain molybdenum oxide as an interface modification layer;

[0015] Copper indium gallium selenide is deposited on the interface modification layer to obtain a light absorption layer;

[0016] A buffer layer, a window layer and a gate electrode are sequentially deposited on the light absorbing layer.

[0017] According to an embodiment of the present disclosure, a direct current magnetron sputtering process is used to deposit molybdenum, wherein the magnetron sputtering current is 0.2-1.5 A; the magnetron sputtering gas pressure is 0.1-1.0 Pa, and the magnetron sputtering time is 15-60 s.

[0018] According to an embodiment of the present disclosure, oxidation treatment of the metal layer includes: immersing the metal layer in an oxidant solution, the immersion time is 5-120s, and the immersion temperature is 20-30°C, wherein the oxidant solution includes: 50-70 parts by mass of an oxidant, 30-95 parts by mass of deionized water; the oxidant includes at least one of hydrogen peroxide, potassium permanganate, and persulfate.

[0019] According to an embodiment of the present disclosure, the band gap width of the interface modification layer is changed by the influence of the immersion time.

[0020] According to an embodiment of the present disclosure, a method for preparing a window layer includes:

[0021] Intrinsic aluminum oxide is deposited on the surface of the buffer layer by magnetron sputtering, wherein the sputtering gas pressure is 0.5-0.8 Pa and the sputtering power is 50-150 W;

[0022] Intrinsic aluminum oxide is deposited on the surface of the buffer layer by magnetron sputtering, wherein the sputtering gas pressure is 0.1-0.5 Pa and the sputtering power is 150-220 W.

[0023] According to an embodiment of the present disclosure, a method for preparing a gate electrode is to sequentially deposit nickel and aluminum on the surface of a window layer, wherein the thickness of the aluminum is 200-1000 Å and the thickness of the aluminum is 3000-18000 Å.

[0024] According to the embodiments of the present disclosure, in the technical solution of the present disclosure, an interface modification layer is introduced between the interface of the conventional substrate and the light absorbing layer, which effectively avoids direct contact between the transparent conductive substrate and the copper indium gallium selenide light absorbing layer. The interface modification layer with stable performance can prevent the diffusion of elements at the back interface of the light absorbing layer, and inhibit the diffusion of GaO at high substrate temperature (greater than 500°C). x The generation of thin-film solar cells (hereinafter referred to as GIGS cells) is achieved by effectively passivating the back interface defects through large-scale regulation of the band structure, while obtaining excellent copper indium gallium selenide crystal quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 is a cross-sectional structural diagram of a thin-film solar cell according to an embodiment of the present disclosure;

[0026] Figure 2 is a light transmission diagram of the interface modification layer in Examples 1-3 of the present disclosure;

[0027] Figure 3 is a light absorption diagram of the interface modification layer in Examples 1-3 of the present disclosure;

[0028] Figure 4 is a cross-sectional electron microscope image of the thin-film solar cell in Example 1 of the present disclosure;

[0029] Figure 5 is a cross-sectional electron microscope image of the light absorption layer in Example 2 of the present disclosure;

[0030] Figure 6 is a cross-sectional electron microscope image of the light absorption layer in Comparative Example 1 of the present disclosure;

[0031] Figure 7 is a cross-sectional electron microscope image of the light absorption layer in Comparative Example 2 of the present disclosure;

[0032] Figure 8 It is a JV curve diagram of Examples 1-3 and Comparative Examples 1 and 2 of the present disclosure;

[0033] Fig. 9 It is a transmittance curve diagram of the thin-film solar cell of Example 2 of the present disclosure. DETAILED DESCRIPTION

[0034] In order to make the objectives, technical solutions and advantages of the present disclosure more clearly understood, the present disclosure is further described in detail below in combination with specific embodiments and with reference to the accompanying drawings.

[0035] The endpoints and any values ​​of the ranges disclosed in this disclosure are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed in this disclosure.

[0036] The terms used herein are only for describing specific embodiments and are not intended to limit the present disclosure. The terms "comprise", "include", etc. used herein indicate the existence of the features, steps, operations and / or components, but do not exclude the existence or addition of one or more other features, steps, operations or components.

[0037] All terms (including technical and scientific terms) used herein have the meanings commonly understood by those skilled in the art unless otherwise defined. It should be noted that the terms used herein should be interpreted as having a meaning consistent with the context of this specification and should not be interpreted in an idealized or overly rigid manner.

[0038] It should be noted that, unless otherwise defined, the technical terms or scientific terms used in the present disclosure shall have the usual meanings understood by persons with ordinary skills in the field to which the present disclosure belongs. If the full text involves descriptions such as "first", "second", etc., the descriptions such as "first", "second", etc. are only used to distinguish similar objects, and cannot be understood as indicating or implying their relative importance, order of precedence, or implicitly indicating the number of technical features indicated. It should be understood that the data described by "first", "second", etc. can be interchangeable under appropriate circumstances.

[0039] In the present disclosure, 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, an electrical connection, or can communicate with each other; it can be a direct connection, or it can be indirectly connected through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements. For ordinary technicians in this field, the specific meanings of the above terms in the present disclosure can be understood according to specific circumstances.

[0040] In the description of the present disclosure, it is necessary to understand that the terms "longitudinal", "length", "circumferential", "front", "rear", "left", "right", "top", "bottom", "inside", "outside", etc., indicating the orientation or positional relationship, are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present disclosure and simplifying the description, and do not indicate or imply that the subsystem or element referred to 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 disclosure.

[0041] Throughout the drawings, the same elements are represented by the same or similar reference numerals. Conventional structures or configurations will be omitted when they may cause confusion in the understanding of the present disclosure. The shapes, sizes, and positional relationships of the components in the drawings do not reflect the actual size, proportion, and actual positional relationship. In addition, in the present disclosure, any reference symbol between brackets should not be constructed as a limitation to the present disclosure.

[0042] Similarly, in order to simplify the present disclosure and help understand one or more of the various disclosed aspects, in the above description of the exemplary embodiments of the present disclosure, the various features of the present disclosure are sometimes grouped together into a single embodiment, figure, or description thereof. The description with reference to the terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" and the like means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present disclosure. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0043] In addition, the technical solutions between the various embodiments can be combined with each other, but it must be based on the fact that ordinary technicians in the field can implement it. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such combination of technical solutions does not exist and is not within the scope of protection required by this disclosure.

[0044] In the meanings of the terms “back field”, “back interface” and the like used in the present disclosure, the direction of “back” is relative to the light absorbing layer.

[0045] In the process of implementing the present disclosure, it was found that the conversion efficiency of the semi-transparent ultra-thin CIGS cell is much lower than that of the conventional structure cell (such as Mo substrate structure). In order to ensure the transmittance of the device's visible light, the thickness of the absorption layer needs to be thinned to convert part of the light into electrical energy so that the remaining light can be used for transmission, which inevitably limits the conversion efficiency. The present disclosure effectively solves the problem of GaO caused by the increase in substrate temperature by introducing an oxide as an interface modification layer between the TCO and the CIGS light absorption layer. x The generation problem is solved, which significantly improves the crystal quality of the CIGS light absorption layer. At the same time, the interface modification layer optimizes the contact performance of the back interface of the CIGS light absorption layer, reduces the interface carrier recombination, and thus greatly improves the overall photoelectric performance of the battery.

[0046] Figure 1 It is a cross-sectional structural diagram of a thin-film solar cell according to an embodiment of the present disclosure.

[0047] The present disclosure proposes a semi-transparent ultra-thin copper indium gallium selenide thin film solar cell, such as Figure 1As shown, it includes a substrate, a light absorption layer, an interface modification layer, a buffer layer, a window layer and a gate electrode. Among them, the substrate is made of a transparent conductive material; the light absorption layer is formed on the substrate, and the material of the light absorption layer is copper indium gallium selenide, which is suitable for absorbing sunlight and generating carriers; the interface modification layer is formed between the substrate and the light absorption layer, which is suitable for providing a crystal plane of the light absorption layer and passivating the contact surface between the substrate and the light absorption layer, preventing the element diffusion of the light absorption layer, and reducing the carrier recombination at the contact surface; the buffer layer is formed on the light absorption layer, which is suitable for forming a potential barrier and adjusting the work function to transmit carriers and form a photocurrent; the window layer is formed on the buffer layer, which is suitable for allowing sunlight to enter and providing a forward bias to prevent the reverse flow of carriers; the gate electrode is formed on the window layer, which is suitable for collecting and transmitting photocurrent.

[0048] According to the embodiments of the present disclosure, in the technical solution of the present disclosure, an interface modification layer is introduced between the interface of the conventional substrate and the light absorbing layer, which effectively avoids direct contact between the transparent conductive substrate and the copper indium gallium selenide light absorbing layer. The interface modification layer with stable performance can prevent the diffusion of elements at the back interface of the light absorbing layer, and inhibit the GaO x The generation of thin-film solar cells (hereinafter referred to as GIGS cells) is achieved by effectively passivating the back interface defects through large-scale regulation of the band structure, while obtaining excellent copper indium gallium selenide crystal quality.

[0049] Figure 4 This is a cross-sectional electron microscope image of the thin-film solar cell in Example 1 of the present disclosure.

[0050] like Figure 4 As shown, the thin film solar cell in Example 1 includes a substrate (FTO), a light absorption layer (GIGS), a buffer layer (CdS), and a window layer (i-ZnO, AZO).

[0051] According to an embodiment of the present disclosure, the thickness of the interface modification layer is 5-50nm, for example, 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, etc.; the thickness of the light absorption layer is 200-700nm, for example, 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, etc. nm, etc.; the thickness of the buffer layer is 20-80nm, for example, it can be 20nm, 25nm, 30nm, 35nm, 40nm, 45nm, 50nm, 55nm, 60nm, 65nm, 70nm, 75nm, 80nm, etc.; the thickness of the window layer is 220-400nm, for example, it can be 220nm, 240nm, 260nm, 280nm, 300nm, 330nm, 350nm, 380nm, 400nm, etc.

[0052] According to an embodiment of the present disclosure, the transparent conductive material includes at least one of indium tin oxide (ITO), fluorine-doped tin oxide (FTO), titanium-doped indium oxide (ITO-Ti), and gallium-doped zinc oxide (GZO); the material of the interface modification layer is molybdenum oxide; the material of the buffer layer includes at least one of cadmium sulfide (CdS), zinc oxysulfide (Zn(O,S)), zinc magnesium oxide (ZnMgO), zinc tin oxide (ZnSnO), and indium sulfide (In2S3); the materials of the window layer are intrinsic zinc oxide (i-ZnO) and aluminum-doped zinc oxide (AZO); and the materials of the gate electrode include nickel and aluminum.

[0053] According to the embodiments of the present disclosure, molybdenum oxide (MoOx) is used as the interface modification layer. Mo and O have better bond energy, and the formed oxide is more stable and will not form oxides with Ga in the light absorption layer. Its higher conduction band can also form a back field, which reduces back interface carrier recombination and passivates back interface defects by optimizing the back interface energy band structure, thereby significantly improving the photoelectric performance of the GIGS battery.

[0054] According to an embodiment of the present disclosure, the band gap width of molybdenum oxide is 2.80-3.40eV, for example, it can be 2.80eV, 2.81eV, 2.90eV, 2.95eV, 3.00eV, 3.05eV, 3.10eV, 3.15eV, 3.20eV, 3.25eV, 3.30eV, 3.36eV, 3.40eV, etc.

[0055] In another aspect of the present disclosure, a method for preparing the aforementioned thin-film solar cell is also proposed, comprising the following steps S201 to S203:

[0056] Step S201: depositing molybdenum on a substrate made of a transparent conductive material to obtain a metal layer, and oxidizing the metal layer to obtain molybdenum oxide as an interface modification layer;

[0057] Step S202: depositing copper indium gallium selenide on the interface modification layer to obtain a light absorption layer;

[0058] Step S203: depositing a buffer layer, a window layer and a gate electrode in sequence on the light absorption layer.

[0059] According to the embodiment of the present disclosure, metal molybdenum is deposited on a substrate and then oxidized to obtain an interface modification layer. An ultra-thin copper indium gallium selenide absorption layer is prepared on the interface modification layer to shorten the deposition time and reduce the production energy and material loss of copper indium gallium selenide solar cells.

[0060] In some specific embodiments, in step S202 , the method for depositing copper indium gallium selenide is a common three-step co-evaporation process.

[0061] According to an embodiment of the present disclosure, a DC magnetron sputtering process is used to deposit molybdenum, wherein the magnetron sputtering current is 0.2-1.5A, for example, it can be 0.2A, 0.4A, 0.6A, 0.8A, 1.0A, 1.1A, 1.2A, 1.3A, 1.4A, 1.5A, etc.; the magnetron sputtering gas pressure is 0.1-1.0Pa, for example, it can be 0.1Pa, 0.2Pa, 0.3Pa, 0.4Pa, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa, 0.9Pa, 1.0Pa, etc.; the magnetron sputtering time is 15-60s, for example, it can be 15s, 20s, 25s, 30s, 35s, 40s, 45s, 50s, 55s, 60s, etc.

[0062] According to an embodiment of the present disclosure, oxidation treatment of the metal layer includes: immersing the metal layer in an oxidant solution, the immersion time is 5-120s, for example, it can be 50s, 10s, 20s, 40s, 60s, 80s, 100s, 120s, etc.; the immersion temperature is 20-30°C, for example, it can be 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, etc.; wherein the oxidant solution includes: 50-70 parts by mass of an oxidant, 30-95 parts by mass of deionized water; the oxidant includes at least one of hydrogen peroxide (H2O2), potassium permanganate (KMnO4), and persulfate (such as ammonium persulfate (NH4)2S2O8).

[0063] According to the embodiments of the present disclosure, the metal layer is wet oxidized using an oxidant solution to change the metal oxidation state to control the energy band structure. The band gap width is changed by the immersion time, and a high-quality oxide interface modification layer can be obtained.

[0064] According to an embodiment of the present disclosure, the band gap width of the interface modification layer is changed by the influence of the immersion time.

[0065] According to an embodiment of the present disclosure, a method for preparing a window layer comprises the following steps:

[0066] Intrinsic aluminum oxide is deposited on the surface of the buffer layer by magnetron sputtering, wherein the sputtering gas pressure is 0.5-0.8Pa, for example, 0.5Pa, 0.6Pa, 0.7Pa, 0.8Pa, etc.; the sputtering power is 50-150W, for example, 50W, 80W, 100W, 130W, 150W, etc.; specifically, at a low frequency of 50-150W, sputtering is performed for 5-10 times, and the trolley runs a distance of 100 cm.

[0067] Intrinsic aluminum oxide is deposited on the surface of the buffer layer by magnetron sputtering, wherein the sputtering pressure is 0.1-0.5 Pa, for example, 0.1 Pa, 0.2 Pa, 0.3 Pa, 0.4 Pa, 0.5 Pa, etc., and the sputtering power is 150-220 W, for example, 150 W, 180 W, 200 W, 210 W, 220 W, etc. Specifically, at a low frequency of 150-220 W, sputtering is performed for 10-30 times, and the trolley runs a distance of 100 cm.

[0068] According to an embodiment of the present disclosure, a method for preparing a gate electrode is to deposit nickel and aluminum on the surface of a window layer in sequence, wherein the thickness of the aluminum is 200-1000Å, for example, 200Å, 220Å, 240Å, 260Å, 280Å, 1000Å, etc.; the thickness of the aluminum is 3000-18000Å, for example, 3000Å, 5000Å, 8000Å, 10000Å, 13000Å, 15000Å, 18000Å, etc.

[0069] It should be noted that the described embodiments are only part of the embodiments of the present disclosure, rather than all of the embodiments. Based on the embodiments of the present disclosure, other embodiments obtained by ordinary technicians in the field without creative work are all within the scope of protection of the present disclosure.

[0070] Example 1

[0071] Step 1: Select FTO conductive glass with a size of 44 mm × 42 mm × 2 mm as the substrate. The thickness of the FTO substrate is 400 nm. Ultrasonic cleaning is performed in deionized water, acetone, and anhydrous ethanol for 30 minutes in sequence to rinse the impurities remaining on the surface. Then, it is blown dry with a clean nitrogen flow and then placed in a high vacuum injection chamber for baking for 20 minutes to remove moisture.

[0072] Step 2: A Mo layer was deposited on the FTO substrate obtained in step 1 using magnetron sputtering technology. The sputtering process parameters were set as follows: sputtering pressure 0.1 Pa, sputtering current 0.5 A, sputtering time 35 s, and a Mo layer with a thickness of 40 nm was obtained.

[0073] Step 3: Prepare an oxidation solution, using 15 parts by mass of H2O2 as an oxidant and 85 parts of deionized water as a solvent. The Mo layer obtained in step 2 was oxidized by immersion for 15 s at room temperature to form a MoOx interface modification layer with a thickness of 40 nm. Subsequently, the surface was quickly rinsed with deionized water to remove the residual H2O2 solution, and then dried with nitrogen.

[0074] Step 4: On the MoOx interface modification layer obtained in step 3, a copper indium gallium selenide (CIGS) light absorption layer is deposited by a three-step co-evaporation process, wherein the substrate temperature of the three-step evaporation is 380°C-500°C-500°C, and the thickness of the absorption layer is about 500 nm.

[0075] Step 5: On the surface of the CIGS absorption layer obtained in step 4, a CdS buffer layer with a thickness of 60 nm is deposited by a chemical bath deposition (CBD) method.

[0076] Step 6: Prepare an intrinsic ZnO layer (i-ZnO) and an aluminum-doped ZnO layer (AZO) as a window layer in sequence. First, a 90 nm thick i-ZnO layer was sputtered on the surface of the sample obtained in step 5 at a sputtering power of 90 W and a gas pressure of 0.8 Pa; then, a 400 nm thick AZO layer was sputtered on the surface of the i-ZnO layer at a sputtering power of 220 W and a gas pressure of 0.3 Pa to form a window layer.

[0077] Step 7: Using electron beam evaporation technology, a Ni-Al gate electrode was deposited on the surface of the sample obtained in step 6. The thickness of the Ni electrode was 500 Å and the thickness of the Al electrode was 12000 Å.

[0078] Example 2

[0079] In this embodiment 2, the difference from embodiment 1 is that the oxidation treatment time of the interface modification layer is adjusted, thereby changing the MoO x The band structure of the interface modification layer. The specific preparation process is as follows:

[0080] Step 1: Select FTO conductive glass with a size of 44 mm × 42 mm × 2 mm as the substrate. The thickness of the FTO substrate is 400 nm. Ultrasonic cleaning is carried out in deionized water, acetone, and anhydrous ethanol for 30 minutes in sequence to rinse the impurities remaining on the surface. Then, it is blown dry with a clean nitrogen flow and then placed in a high vacuum injection chamber for baking for 20 minutes to remove moisture.

[0081] Step 2: A Mo layer was deposited on the FTO substrate obtained in step 1 using magnetron sputtering technology. The sputtering process parameters were set as follows: sputtering pressure 0.1 Pa, sputtering current 0.5 A, sputtering time 35 s, and a Mo layer with a thickness of 40 nm was obtained.

[0082] Step 3: Prepare an oxidation solution, using 15 parts by mass of H2O2 as an oxidant and 85 parts of deionized water as a solvent. The Mo layer obtained in step 2 was oxidized by an immersion method, with an immersion time of 30 s and a temperature of room temperature to form a MoOx interface modification layer with a thickness of 40 nm. Subsequently, the surface was quickly rinsed with deionized water to remove the residual H2O2 solution, and then dried with nitrogen.

[0083] Step 4: On the MoOx interface modification layer obtained in step 3, a copper indium gallium selenide (CIGS) absorption layer is deposited by a three-step co-evaporation process, the three-step evaporation substrate temperature is 380°C-500°C-500°C, and the absorption layer thickness is about 500 nm.

[0084] Step 5: On the surface of the CIGS absorption layer obtained in step 4, a CdS buffer layer with a thickness of 60 nm is deposited by a chemical bath deposition (CBD) method.

[0085] Step 6: Prepare an intrinsic ZnO layer (i-ZnO) and an aluminum-doped ZnO layer (AZO) as window layers in sequence. First, a 90 nm thick i-ZnO layer was sputtered on the surface of the sample obtained in step 5 at a sputtering power of 90 W and a gas pressure of 0.8 Pa; then, a 400 nm thick AZO layer was sputtered on the surface of the i-ZnO layer at a sputtering power of 220 W and a gas pressure of 0.3 Pa.

[0086] Step 7: Using electron beam evaporation technology, a Ni-Al gate electrode was deposited on the surface of the sample obtained in step 6. The thickness of the Ni electrode was 500 Å and the thickness of the Al electrode was 12000 Å.

[0087] Example 3

[0088] In this embodiment 3, the difference from the embodiment 1 is that the oxidation treatment time of the interface modification layer is adjusted, thereby changing the MoO x The band structure of the interface modification layer. The specific preparation process is as follows:

[0089] Step 1: Select FTO conductive glass with a size of 44 mm × 42 mm × 2 mm as the substrate. The thickness of the FTO substrate is 400 nm. Ultrasonic cleaning is performed in deionized water, acetone, and anhydrous ethanol for 30 minutes in sequence to rinse the impurities remaining on the surface. Then, it is blown dry with a clean nitrogen flow and then placed in a high vacuum injection chamber for baking for 20 minutes to remove moisture.

[0090] Step 2: A Mo layer was deposited on the FTO substrate obtained in step 1 using magnetron sputtering technology. The sputtering process parameters were set as follows: sputtering pressure 0.1 Pa, sputtering current 0.5 A, sputtering time 35 s, and a Mo layer with a thickness of 40 nm was obtained.

[0091] Step 3: Prepare an oxidation solution, using 15 parts by mass of H2O2 as an oxidant and 85 parts of deionized water as a solvent. The Mo layer obtained in step 2 was oxidized by an immersion method, with an immersion time of 60 s and a temperature of room temperature to form a MoOx interface modification layer with a thickness of 40 nm. Subsequently, the surface was quickly rinsed with deionized water to remove the residual H2O2 solution, and then dried with nitrogen.

[0092] Step 4: On the MoOx interface modification layer obtained in step 3, a copper indium gallium selenide (CIGS) absorption layer is deposited by a three-step co-evaporation process, the three-step evaporation substrate temperature is 380°C-500°C-500°C, and the absorption layer thickness is about 500 nm.

[0093] Step 5: On the surface of the CIGS absorption layer obtained in step 4, a CdS buffer layer with a thickness of 60 nm is deposited by a chemical bath deposition (CBD) method.

[0094] Step 6: Prepare an intrinsic ZnO layer (i-ZnO) and an aluminum-doped ZnO layer (AZO) as window layers in sequence. First, a 90 nm thick i-ZnO layer was sputtered on the surface of the sample obtained in step 5 at a sputtering power of 90 W and a gas pressure of 0.8 Pa; then, a 400 nm thick AZO layer was sputtered on the surface of the i-ZnO layer at a sputtering power of 220 W and a gas pressure of 0.3 Pa.

[0095] Step 7: Using electron beam evaporation technology, a Ni-Al gate electrode was deposited on the surface of the sample obtained in step 6. The thickness of the Ni electrode was 500 Å and the thickness of the Al electrode was 12000 Å.

[0096] Comparative Example 1

[0097] In this comparative example 1, the difference from Example 1 is that the oxidation treatment time of the interface modification layer is adjusted. The specific preparation process is as follows:

[0098] Step 1: Select FTO conductive glass with a size of 44 mm × 42 mm × 2 mm as the substrate. The thickness of the FTO substrate is 400 nm. Ultrasonic cleaning is carried out in deionized water, acetone, and anhydrous ethanol for 30 minutes in sequence to rinse the impurities remaining on the surface. Then, it is blown dry with a clean nitrogen flow and then placed in a high vacuum injection chamber for baking for 20 minutes to remove moisture.

[0099] Step 2: A Mo layer was deposited on the FTO substrate obtained in step 1 using magnetron sputtering technology. The sputtering process parameters were set as follows: sputtering pressure 0.1 Pa, sputtering current 0.5 A, sputtering time 35 s, and a Mo layer with a thickness of 40 nm was obtained.

[0100] Step 3: Prepare an oxidation solution, using 15 parts by mass of H2O2 as an oxidant and 85 parts of deionized water as a solvent. The Mo layer obtained in step 2 was oxidized by an immersion method, with an immersion time of 30 s and a temperature of room temperature to form a MoOx interface modification layer with a thickness of 40 nm. Subsequently, the surface was quickly rinsed with deionized water to remove the residual H2O2 solution, and then dried with nitrogen.

[0101] Step 4: On the MoOx interface modification layer obtained in step 3, a copper indium gallium selenide (CIGS) absorption layer is deposited by a three-step co-evaporation process. The substrate temperature of the three-step evaporation is 380°C-420°C-420°C, and the thickness of the absorption layer is about 500 nm.

[0102] Step 5: On the surface of the CIGS absorption layer obtained in step 4, a CdS buffer layer with a thickness of 60 nm is deposited by a chemical bath deposition (CBD) method.

[0103] Step 6: Prepare an intrinsic ZnO layer (i-ZnO) and an aluminum-doped ZnO layer (AZO) as window layers in sequence. First, a 90 nm thick i-ZnO layer was sputtered on the surface of the sample obtained in step 5 at a sputtering power of 90 W and a gas pressure of 0.8 Pa; then, a 400 nm thick AZO layer was sputtered on the surface of the i-ZnO layer at a sputtering power of 220 W and a gas pressure of 0.3 Pa.

[0104] Step 7: Using electron beam evaporation technology, a Ni-Al gate electrode was deposited on the surface of the sample obtained in step 6. The thickness of the Ni electrode was 500 Å and the thickness of the Al electrode was 12000 Å.

[0105] Comparative Example 2

[0106] In this comparative example 2, the difference from Example 1 is that the preparation of the interface modification layer is omitted. The specific preparation process is as follows:

[0107] Step 1: Select FTO conductive glass with a size of 44 mm × 42 mm × 2 mm as the substrate. The thickness of the FTO substrate is 400 nm. Ultrasonic cleaning is performed in deionized water, acetone, and anhydrous ethanol for 30 minutes in sequence to rinse the impurities remaining on the surface. Then, it is blown dry with a clean nitrogen flow and then placed in a high vacuum injection chamber for baking for 20 minutes to remove moisture.

[0108] Step 2: On the FTO substrate obtained in step 1, a copper indium gallium selenide (CIGS) absorption layer is deposited by a three-step co-evaporation process, the three-step evaporation substrate temperature is 380°C-420°C-420°C, and the absorption layer thickness is about 500 nm.

[0109] Step 3: On the surface of the CIGS absorption layer obtained in step 2, a CdS buffer layer with a thickness of 60 nm is deposited by a chemical bath deposition (CBD) method.

[0110] Step 4: Prepare an intrinsic ZnO layer (i-ZnO) and an aluminum-doped ZnO layer (AZO) as window layers in sequence. First, a 90 nm thick i-ZnO layer was sputtered on the surface of the sample obtained in step 3 at a sputtering power of 90 W and a gas pressure of 0.8 Pa; then, a 400 nm thick AZO layer was sputtered on the surface of the i-ZnO layer at a sputtering power of 220 W and a gas pressure of 0.3 Pa.

[0111] Step 5: Using electron beam evaporation technology, a Ni-Al gate electrode is deposited on the surface of the sample obtained in step 4. The thickness of the Ni electrode is 500 Å, and the thickness of the Al electrode is 12000 Å.

[0112] Figure 2 is a light transmission diagram of the interface modification layer in Examples 1-3 of the present disclosure, Figure 3 It is a light absorption diagram of the interface modification layer in Examples 1-3 of the present disclosure.

[0113] like Figure 2 , Figure 3 As shown in the figure, as the oxidation treatment time increases, the oxidation state of MoOx increases, the band gap of the interface modification layer film widens from 2.81eV to 3.36eV, and the corresponding film transmittance increases. When the oxidation treatment time reaches 35 s, the overall transmittance of the interface modification layer exceeds 80%, which will not affect the back-illuminated performance of the ultra-thin CIGS battery.

[0114] Figure 5 , Figure 6 , Figure 7 They are cross-sectional electron microscope images of the light absorption layer in Example 2 of the present disclosure and Comparative Examples 1 and 2 respectively.

[0115] like Figure 5-7 As shown in the figure, by comparing the surface morphology and cross-sectional grains of the samples, it is shown that, without considering the problem of GaOx formation caused by direct contact between CIGS and TCO at high substrate temperature, high substrate temperature significantly improves the crystallization quality of the absorption layer compared to low substrate temperature, regardless of the presence of a MoOx interface modification layer, and forms a vertically penetrating large grain structure. Such large grains help improve the carrier transport efficiency in GIGS batteries and reduce grain boundary recombination.

[0116] The photovoltaic performance test was performed on the GIG cells prepared in Examples 1-3 and Comparative Examples 1 and 2. The photovoltaic parameters are recorded in Table 1 below.

[0117] Table 1:

[0118]

[0119] Figure 8 It is a JV curve diagram of Examples 1-3 and Comparative Examples 1 and 2 of the present disclosure.

[0120] like Figure 8 As shown in Table 1, the device containing the MoOx interface modification layer exhibits a higher open circuit voltage (Voc) and fill factor (FF). This is because the higher substrate temperature can improve the crystallization quality of the CIGS layer, but at the same time promotes the generation of a large amount of GaOx at the back interface, thereby aggravating the recombination of interface carriers and causing a decrease in battery performance. By introducing a MoOx interface modification layer between the CIGS light absorption layer and the TCO substrate, direct contact between the two is successfully avoided, the generation of GaOx is suppressed, and the carrier recombination phenomenon at the back interface is significantly reduced. Further analysis shows that by optimizing the oxidation treatment time, the open circuit voltage of the battery is increased from 476 mV to 600 mV. The MoOx band gap width prepared in Example 2 reaches 3.15 eV, and has an optimal band structure. Its perfect conduction band position can form an effective back field with CIGS, reduce the back interface carrier recombination, and play an interface passivation role, thereby enhancing the overall photoelectric performance of the device.

[0121] Fig. 9 It is a transmittance curve diagram of the thin-film solar cell of Example 2 of the present disclosure.

[0122] As shown in the figure, in the 600-780nm band, Example 2 has good light transmission performance, and the maximum transmittance can reach 18%, which has important application potential in fields such as building integrated photovoltaics (BIPV). It can be seen that the semi-transparent ultra-thin CIGS thin-film solar cell proposed in the present disclosure not only improves the photoelectric conversion efficiency, but also shows broad prospects in practical application scenarios.

[0123] The specific embodiments described above further illustrate the purpose, technical solutions and beneficial effects of the present disclosure. It should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present disclosure should be included in the protection scope of the present disclosure.

Claims

1. A semi-transparent ultra-thin copper indium gallium selenide thin film solar cell, comprising: a substrate made of a transparent conductive material; A light absorbing layer is formed on the substrate, and the light absorbing layer is copper indium gallium selenide, which is suitable for absorbing sunlight and generating carriers; An interface modification layer is formed between the substrate and the light absorbing layer, and is suitable for providing a crystal plane for the light absorbing layer, passivating the contact surface between the substrate and the light absorbing layer, preventing element diffusion of the light absorbing layer, and reducing carrier recombination at the contact surface; A buffer layer, formed on the light absorbing layer, adapted to form a potential barrier and adjust a work function to transport the carriers to form a photocurrent; A window layer, formed on the buffer layer, adapted to allow sunlight to enter and provide a forward bias to prevent the carriers from flowing in the opposite direction; A gate electrode is formed on the window layer and is suitable for collecting and transmitting the photocurrent.

2. The thin film solar cell according to claim 1, wherein: The thickness of the interface modification layer is 5-50 nm, the thickness of the light absorption layer is 200-700 nm, the thickness of the buffer layer is 20-80 nm, and the thickness of the window layer is 220-400 nm.

3. The thin film solar cell according to claim 1, wherein: The transparent conductive material comprises at least one of indium tin oxide, fluorine-doped tin oxide, titanium-doped indium oxide, and gallium-doped zinc oxide; The material of the interface modification layer is molybdenum oxide; The material of the buffer layer includes at least one of cadmium sulfide, zinc oxysulfide, zinc magnesium oxide, zinc tin oxide, and indium sulfide; The materials of the window layer are intrinsic zinc oxide and aluminum-doped zinc oxide; The gate electrode is made of nickel and aluminum.

4. The thin film solar cell according to claim 3, wherein: The band gap width of the molybdenum oxide is 2.80-3.40 eV.

5. A method for preparing a thin film solar cell according to any one of claims 1 to 4, comprising: Depositing molybdenum on a substrate made of a transparent conductive material to obtain a metal layer, and performing oxidation treatment on the metal layer to obtain molybdenum oxide as an interface modification layer; Depositing copper indium gallium selenide on the interface modification layer to obtain a light absorption layer; A buffer layer, a window layer and a gate electrode are sequentially deposited on the light absorbing layer.

6. The preparation method according to claim 1, wherein Molybdenum is deposited by a direct current magnetron sputtering process, wherein the magnetron sputtering current is 0.2-1.5A; the magnetron sputtering gas pressure is 0.1-1.0Pa; and the magnetron sputtering time is 15-60s.

7. The preparation method according to claim 5, wherein: The oxidation treatment of the metal layer includes: immersing the metal layer in an oxidant solution, the immersion time is 5-120s, and the immersion temperature is 20-30°C, wherein the oxidant solution includes: 50-70 parts by mass of an oxidant and 30-95 parts by mass of deionized water; the oxidant includes at least one of hydrogen peroxide, potassium permanganate, and persulfate. 8 . The preparation method according to claim 7 , wherein the band gap width of the interface modification layer is changed by the immersion time.

9. The preparation method according to claim 5, wherein: The preparation method of the window layer comprises: Depositing intrinsic aluminum oxide on the surface of the buffer layer by magnetron sputtering, wherein the sputtering pressure is 0.5-0.8 Pa and the sputtering power is 50-150 W; Intrinsic aluminum oxide is deposited on the surface of the buffer layer by magnetron sputtering, wherein the sputtering pressure is 0.1-0.5 Pa and the sputtering power is 150-220 W.

10. The preparation method according to claim 5, wherein: The method for preparing the gate electrode is to deposit nickel and aluminum in sequence on the surface of the window layer, wherein the thickness of the aluminum is 200-1000 Å and the thickness of the aluminum is 3000-18000 Å.

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