A cadmium telluride thin film cell and a method of making the same

Abstract

The application relates to the technical field of thin-film batteries, and discloses a cadmium telluride thin-film battery and a preparation method thereof. The cadmium telluride thin-film battery comprises, from bottom to top, a base layer, a conductive layer, a high-resistance layer, a window layer, an absorption layer, a first back contact layer, a second back contact layer and a back electrode layer. The first back contact layer comprises a first back contact layer material doped with a first element, and the second back contact layer comprises a second back contact layer material doped with a second element. The doping content of the second element is higher than that of the first element. The first element has a low content and diffuses to the absorption layer, reduces Cu defects introduced by excessive doping, improves the performance of the absorption layer and the stability of the battery. The second element has a high content, which is beneficial to increasing the carrier concentration and conductivity of the second back contact layer, improving the contact performance between the second contact layer and the first back contact layer and the back electrode layer, reducing the contact barrier, improving the hole carrier transport, and improving the efficiency and stability of the battery.

Description

Technical Field

[0001] This invention relates to the field of thin-film battery technology, specifically to a cadmium telluride thin-film battery and its preparation method. Background Technology

[0002] Cadmium telluride (CdTe) thin-film batteries are a type of compound semiconductor thin-film battery that uses CdTe as the absorber layer. They have attracted widespread attention due to their high conversion efficiency and low cost.

[0003] The typical basic structure of a CdTe thin-film battery is: a conductive glass layer - a CdS window layer - a CdTe absorber layer - a back contact layer - a back electrode layer. In existing technologies, copper is often introduced into the back contact layer. On the one hand, copper diffuses from the back contact layer to the absorber layer, increasing the carrier concentration in the absorber layer and improving... pn On the one hand, the built-in potential of the back contact layer improves battery efficiency; on the other hand, by doping the back contact layer itself, the carrier concentration of the back contact layer is increased, the back contact barrier is reduced, and hole carrier transport is improved, further enhancing battery efficiency. However, the currently used single-layer back contact layer doping and one-step annealing diffusion process cannot simultaneously achieve low Cu concentration doping (<10) in the absorber layer. 18 cm -3 ) and high Cu concentration doping in the back contact layer (>10) 20 cm -3 The requirements are that there are problems such as low battery efficiency and poor battery stability.

[0004] Therefore, how to prepare cadmium telluride thin-film batteries with high efficiency and good stability is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0005] In view of this, the present invention provides a cadmium telluride thin-film battery with high battery efficiency and good stability.

[0006] The present invention also provides a method for preparing the above-mentioned cadmium telluride thin-film battery.

[0007] In a first aspect, the present invention provides a cadmium telluride thin-film battery, wherein the cadmium telluride thin-film battery comprises, from bottom to top, a base layer, a transparent conductive layer, a high-resistivity layer, a window layer, an absorption layer, a first back contact layer, a second back contact layer, and a back electrode layer; the first back contact layer comprises a first back contact layer material doped with a first element, and the second back contact layer comprises a second back contact layer material doped with a second element.

[0008] The doping concentration of the second element is higher than that of the first element;

[0009] In the first back contact layer, the content of the first dopant element is 0.00001wt%-0.01wt%.

[0010] In some optional embodiments, the ratio of the doping content of the first element to the doping content of the second element is less than 0.5.

[0011] In some optional embodiments, the ratio of the doping content of the first element to the doping content of the second element is less than 0.1.

[0012] In some optional embodiments, the ratio of the doping content of the first element to the doping content of the second element is less than 0.001.

[0013] In some optional embodiments, the ratio of the doping content of the first element to the doping content of the second element is less than 0.0001.

[0014] In some optional embodiments, the content of the second doping element in the second back contact layer is 0.001wt%-3wt%.

[0015] In some optional embodiments, the first element and the second element are each independently selected from at least one of the group VA elements, the group IB elements.

[0016] In some optional embodiments, the first element and the second element are each independently selected from at least one of Cu, Ag, N, P, As, Sb.

[0017] It should be noted that in the present application, the material of the transparent conductive layer includes FTO; wherein, the FTO is fluorine-doped SnO2 conductive glass; the material of the high resistance layer includes SnO2; the material of the window layer includes at least one of CdSe, CdSe:O; the material of the absorption layer includes CdTe; the material of the first back contact layer includes at least one of ZnTe, CdZnTe; the material of the second back contact layer includes ZnTe; the material of the back electrode layer includes MoAl.

[0018] In some optional embodiments, the thickness of the base layer is 2mm-3.2mm.

[0019] In some optional embodiments, the thickness of the conductive layer is 100nm-600nm.

[0020] In some optional embodiments, the thickness of the high resistance layer is 20nm-80nm.

[0021] In some optional embodiments, the thickness of the window layer is 40nm-300nm.

[0022] In some optional embodiments, the thickness of the absorption layer is 2μm-5μm.

[0023] In some optional embodiments, the thickness of the first back contact layer is 5nm-40nm.

[0024] In some optional embodiments, the thickness of the second back contact layer is 5nm-40nm.

[0025] In some optional embodiments, the thickness of the back electrode layer is 80nm-300nm.

[0026] In the second aspect, the application provides a preparation method of the cadmium telluride thin film battery in the first aspect, comprising the following steps:

[0027] (1) depositing a transparent conductive layer, a high resistance layer, a window layer and an absorption layer on a base layer in sequence, and then performing chlorine treatment to obtain a to-be-treated battery A;

[0028] (2) depositing a first back contact layer on the absorption layer of the to-be-treated battery A, and then performing first photothermal treatment to obtain a to-be-treated battery B;

[0029] (3) depositing a second back contact layer on the first back contact layer of the to-be-treated battery B, and then performing second photothermal treatment to form a second back contact layer, thereby obtaining a to-be-treated battery C;

[0030] (4) depositing a back electrode layer on the second back contact layer of the to-be-treated battery C;

[0031] The temperature of the first photothermal treatment is higher than the temperature of the second photothermal treatment.

[0032] In some optional embodiments, the temperature of the first photothermal treatment is 250℃-450℃, and the time is 1min-60min.

[0033] In some optional embodiments, the light intensity of the first photothermal treatment is 0.1-2 suns.

[0034] In some optional embodiments, the temperature of the second photothermal treatment is 100℃-400℃, and the time is 1min-60min.

[0035] In some optional embodiments, the light intensity of the second photothermal treatment is 0.1-2 suns.

[0036] It should be noted that the standard sunlight of the application is under AM1.5, and the light intensity is 1000W / m 2 .

[0037] In some optional embodiments, the light source of the first photothermal treatment and the light source of the second photothermal treatment are each independently selected from at least one of a halogen lamp, a tungsten lamp, a xenon lamp and an LED lamp.

[0038] Compared with the prior art, the technical scheme of the present application has the following advantages:

[0039] 1. The cadmium telluride thin film battery provided by the present application comprises, from bottom to top, a base layer, a conductive layer, a high resistance layer, a window layer, an absorption layer, a first back contact layer, a second back contact layer, and a back electrode layer; the first back contact layer comprises a first back contact layer material doped with a first element, and the second back contact layer comprises a second back contact layer material doped with a second element; the doping content of the second element is higher than that of the first element; the content of the first element is relatively low, diffuses to the absorption layer, reduces the Cu defects introduced by excessive doping, improves the performance of the absorption layer, improves the stability of the battery, and controls the content of the first doping element to be 0.00001wt%-0.01wt%; too low cannot meet the doping requirements, and too high will lead to excessive content of the doping element diffused to the absorption layer, form other defects, reduce the carrier concentration, and result in poor battery efficiency and stability; the content of the second element is relatively high, which is conducive to increasing the carrier concentration and electrical conductivity of the second back contact layer, improving the contact performance between the second contact layer and the first back contact layer and the back electrode layer, reducing the contact barrier, improving the hole carrier transport, and improving the battery efficiency and stability.

[0040] 2. The preparation method of the cadmium telluride thin film battery provided by the present application controls the temperature of the first photothermal treatment to be higher than that of the second photothermal treatment, which is conducive to the diffusion of the first element to the absorption layer, improves the carrier concentration of the absorption layer, and improves the battery efficiency; the temperature of the second photothermal treatment is relatively low, which ensures that the second element cannot diffuse to the absorption layer, and at the same time, the appropriate lower photothermal treatment temperature realizes the improvement of the crystallization performance of the second back contact layer material, improves the contact between the second back contact layer and the back electrode layer, further realizes the improvement of the power generation efficiency of the battery and improves the stability; the present application adopts a photothermal treatment process to replace the traditional heat treatment process, realizes more uniform diffusion and distribution of the doping elements; at the same time, under illumination, photogenerated carriers and photogenerated potentials are formed, the acceptor (such as Cu Cd - forms a hole) is formed, the carrier concentration is improved, and the battery efficiency and stability are further improved. BRIEF DESCRIPTION OF DRAWINGS

[0041] In order to more clearly illustrate the specific embodiments of the present application or the technical scheme in the prior art, the drawings needed in the following specific embodiments or prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and those skilled in the art can also obtain other drawings according to these drawings without creating any creative labor.

[0042] Figure 1 is a schematic diagram of the photothermal treatment equipment of the present application comparative example 1 (a) and example 1 (b).

[0043] Figure 2 is a structure diagram of a cadmium telluride thin film battery prepared by an embodiment of the present application;

[0044] Figure 3 is a flow chart of a cadmium telluride thin film preparation method of an embodiment of the present application;

[0045] Figure 4 is a structure diagram of a cadmium telluride thin film battery prepared by Comparative Example 1 of the present application;

[0046] Figure 5 is a flow chart of a cadmium telluride thin film preparation method of Comparative Example 1 of the present application;

[0047] Figure 6 is a normalized battery efficiency diagram of Comparative Example 1 (a) and Example 1 (b) of the present application;

[0048] Explanation of Reference Signs:

[0049] Glass substrate 1, transparent conductive layer 2, high resistance layer 3, window layer 4, absorption layer 5, first back contact layer 6, second back contact layer 8, back electrode layer 7, heating device 9, battery sample 10, heat source 11, light source 12. DETAILED DESCRIPTION

[0050] The following examples are provided to better further understand the present application and are not limited to the best mode contemplated, do not limit the scope of the present application, and any person skilled in the art under the guidance of the present application or combining the present application with other prior art features can obtain any product identical or similar to the present application, which falls within the scope of the present application.

[0051] The specific experimental steps or conditions not mentioned in the examples can be performed according to the conventional experimental steps described in the literature in the art or the operation or conditions. The reagents or instruments not mentioned by the manufacturer are conventional reagent products that can be obtained by market purchase.

[0052] It should be noted that, as shown in Figure 1 the present application, the light source 12 in the heating device 9 is at least one of a tungsten lamp, a halogen lamp, a xenon lamp, and an LED lamp to simulate a sunlight source, is located at the glass light receiving surface position of the battery sample 10, and is in an array distribution; the heat source 11 in the heating device in Comparative Example 1 is a conventional heating wire; by integrating the photo-thermal activation process into the heat treatment process, the additional activation equipment and process requirements are avoided, the online activation equipment investment of nearly ten million yuan is reduced, and the battery manufacturing cost and market competitiveness are further reduced.

[0053] The present application will be further described in detail below in combination with specific embodiments, which cannot be understood as limiting the scope of the present application.

[0054] Example 1

[0055] like Figure 2 As shown, this embodiment provides a cadmium telluride thin-film battery, which consists of a glass substrate 1, a transparent conductive layer 2, a high-resistivity layer 3, a window layer 4, an absorption layer 5, a first back contact layer 6, a second back contact layer 8, and a back electrode layer 7, from bottom to top.

[0056] like Figure 3 As shown, this embodiment provides a method for preparing a cadmium telluride thin-film battery, including the following steps:

[0057] (1) A 3.2mm thick ultra-white soda-lime glass substrate is used;

[0058] (2) A transparent conductive layer is obtained by depositing SnO2:F (FTO) with a thickness of 100nm-600nm on a glass substrate;

[0059] (3) A high-resistivity layer is obtained by depositing SnO2 with a thickness of 20nm-80nm on the transparent conductive layer;

[0060] (4) A CdSe layer with a thickness of 40 nm-300 nm is deposited on the high-resistivity layer to obtain a window layer;

[0061] (5) A CdTe layer with a thickness of 2μm-5μm is deposited on the window layer, and the layer is treated at 400℃-500℃ for 5min-60min in a CdCl2 atmosphere. Then, the cadmium telluride surface is treated with 0.75wt% dilute hydrochloric acid solution to obtain the absorption layer.

[0062] (6) Deposit a ZnTe with a Cu content of 0.0001wt%-0.001wt% on the absorption layer with a thickness of 5nm-40nm, and then photothermally treat it at 350℃ for 25min. The light source is a tungsten lamp with a light intensity of 0.1-1 suns to obtain the first back contact layer.

[0063] (7) Deposit ZnTe with a thickness of 5nm-30nm and an Ag content of 0.1wt%-0.5wt% on the first back contact layer, and then perform photothermal treatment at 100℃-200℃ for 5min-30min. The light source is a tungsten lamp with a light intensity of 0.1-1 suns to obtain the second back contact layer.

[0064] (8) A MoAl layer with a thickness of 80nm-300nm is deposited on the second back contact layer to obtain the back electrode deposition.

[0065] Example 2

[0066] like Figure 3 As shown, this embodiment provides a method for preparing a cadmium telluride thin-film battery, including the following steps:

[0067] (1) using a thickness of 3.2 mm super white sodium-calcium glass substrate;

[0068] (2) on the glass substrate deposited thickness of 100 nm-600 nm SnO2:F (FTO), get transparent conductive layer;

[0069] (3) on the transparent conductive layer deposited thickness of 20 nm-80 nm SnO2, get high resistance layer;

[0070] (4) on the high resistance layer deposited thickness of 40 nm-300 nm CdSe, get window layer;

[0071] (5) on the window layer deposited thickness of 2 μm-5 μm CdTe, in CdCl2 atmosphere 400 ℃-500 ℃ processing 5 min-60 min, then using 0.75 wt% dilute hydrochloric acid solution on the surface of cadmium telluride processing, get absorption layer;

[0072] (6) on the absorption layer deposited thickness of 5 nm-20 nm doped As content of 0.00001 wt%-0.0001 wt% of ZnTe, then in 260 ℃-400 ℃ light heat treatment 1 min-20 min, light source is xenon lamp, light intensity is 0.1-1 sun, get the first back contact layer;

[0073] (7) on the first back contact layer deposited thickness of 5 nm-20 nm doped N content of 0.01 wt%-1 wt% of ZnTe, then in 200 ℃-240 ℃ light heat treatment 5 min-20 min, light source is xenon lamp, light intensity is 0.1-1 sun, get the second back contact layer;

[0074] (8) on the second back contact layer deposited thickness of 80 nm-300 nm MoAl, get back electrode deposition.

[0075] Example 3

[0076] As Figure 3 shown, the embodiment provides a preparation method of cadmium telluride thin film battery, comprising the following steps:

[0077] (1) using a thickness of 3.2 mm super white sodium-calcium glass substrate;

[0078] (2) on the glass substrate deposited thickness of 100 nm-600 nm SnO2:F (FTO), get transparent conductive layer;

[0079] (3) on the transparent conductive layer deposited thickness of 20 nm-80 nm SnO2, get high resistance layer;

[0080] (4) A CdSe layer with a thickness of 40 nm-300 nm is deposited on the high-resistivity layer to obtain a window layer;

[0081] (5) Deposit a CdTe layer with a thickness of 2μm-5μm on the window layer, treat it at 400℃-500℃ for 5-60min in a CdCl2 atmosphere, and then treat the cadmium telluride surface with 0.75wt% dilute hydrochloric acid solution to obtain the absorption layer.

[0082] (6) Deposit CdZnTe with a thickness of 5nm-20nm and a doped P content of 0.00001wt%-0.001wt% on the absorption layer, and then photothermally treat it at 250℃-350℃ for 5min-60min. The light source is an LED lamp with a light intensity of 0.1-1 suns to obtain the first back contact layer.

[0083] (7) Deposit ZnTe with a thickness of 5nm-40nm and a doped Sb content of 0.01wt%-1wt% on the first back contact layer, and then perform photothermal treatment at 200℃-240℃ for 5min-60min. The light source is an LED lamp with a light intensity of 0.1-1 suns to obtain the second back contact layer.

[0084] (8) A MoAl layer with a thickness of 80nm-300nm is deposited on the second back contact layer to obtain the back electrode deposition.

[0085] Comparative Example 1

[0086] like Figure 4 As shown, this comparative example provides a cadmium telluride thin-film battery, which consists of a glass substrate 1, a transparent conductive layer 2, a high-resistivity layer 3, a window layer 4, an absorption layer 5, a first back contact layer 6, and a back electrode layer 8, from bottom to top.

[0087] like Figure 5 As shown in the comparative example, this invention provides a method for preparing a cadmium telluride thin-film battery, comprising the following steps:

[0088] (1) A 3.2mm thick ultra-white soda-lime glass substrate is used;

[0089] (2) A transparent conductive layer is obtained by depositing SnO2:F (FTO) with a thickness of 100nm-600nm on a glass substrate;

[0090] (3) A high-resistivity layer is obtained by depositing SnO2 with a thickness of 20nm-80nm on the transparent conductive layer;

[0091] (4) A CdSe layer with a thickness of 40 nm-300 nm is deposited on the high-resistivity layer to obtain a window layer;

[0092] (5) depositing CdTe with a thickness of 2 μm-5 μm on the window layer, treating at 400℃-500℃ for 5 min-60 min under CdCl2 atmosphere, and then treating the surface of the cadmium telluride with 0.75 wt% dilute hydrochloric acid solution to obtain the absorption layer;

[0093] (6) depositing ZnTe doped with Cu with a content of 0.1 wt%-1 wt% with a thickness of 5 nm-20 nm on the absorption layer, and then heat treating at 200℃-300℃ for 10 min-60 min to obtain the first back contact layer;

[0094] (7) depositing MoAl with a thickness of 80 nm-300 nm on the first back contact layer to obtain the back electrode.

[0095] Comparative Example 2

[0096] This comparative example provides a preparation method of a cadmium telluride thin film battery, which is basically the same as the steps of Example 1, and the only difference is that the content of the first element Cu is 0.015 wt%-0.1%.

[0097] Comparative Example 3

[0098] This comparative example provides a preparation method of a cadmium telluride thin film battery, which is basically the same as the steps of Example 1, and the only difference is that the content of the first element Cu is 0.6 wt%.

[0099] Comparative Example 4

[0100] This comparative example provides a preparation method of a cadmium telluride thin film battery, which is basically the same as the steps of Comparative Example 1, and the only difference is that the temperature of the second light-heat treatment is 400℃.

[0101] Experimental Example

[0102] The cadmium telluride thin film batteries prepared in the above Examples 1-4 and Comparative Examples 1-4 were subjected to battery efficiency tests according to IEC61215, and after normalization calculation, the results are shown in the following table and Figure 6 The aging attenuation rate=(normalized battery efficiency before aging-100h normalized battery efficiency after aging) / normalized battery efficiency before aging×100%.

[0103] Table 1 Battery efficiency test results of each example and comparative example

[0104]

[0105] From the above table and Figure 6It can be seen that the cadmium telluride thin film battery prepared in Examples 1-3 has high normalized efficiency of 1.04-1.06 and good stability, which is conducive to improving the overall power generation efficiency of the battery in a long life (nearly 30 years) cycle; compared with Example 1, the aging efficiency of Comparative Examples 1-3 is significantly reduced after 100h accelerated aging, and the battery stability is poor, because the first element content is high, the content diffused to the absorption layer is too high, other defects are formed, the carrier is reduced, and the battery efficiency and stability are poor; the second temperature of Comparative Example 4 is high, and the second element also diffuses to the absorption layer, resulting in poor battery efficiency and stability.

[0106] Obviously, the above examples are only examples for the sake of clarity, and are not limitations on the embodiments. For those skilled in the art, other different forms of changes or variations can also be made on the basis of the above description. All embodiments do not need and cannot be exhausted. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A cadmium telluride thin-film battery, characterized in that, The cadmium telluride thin-film battery comprises, from bottom to top, a base layer, a transparent conductive layer, a high-resistivity layer, a window layer, an absorption layer, a first back contact layer, a second back contact layer, and a back electrode layer; the first back contact layer comprises a first back contact layer material doped with a first element, and the second back contact layer comprises a second back contact layer material doped with a second element. The doping content of the second element is higher than that of the first element; In the first back contact layer, the content of the first element is 0.00001wt%-0.01wt%.

2. The cadmium telluride thin-film battery according to claim 1, characterized in that, The ratio of the doping content of the first element to the doping content of the second element is less than 0.

5.

3. The cadmium telluride thin-film battery according to claim 2, characterized in that, The ratio of the doping content of the first element to the doping content of the second element is less than 0.

1.

4. The cadmium telluride thin-film battery according to any one of claims 1-3, characterized in that, In the second back contact layer, the content of the second element is 0.001wt%-3wt%.

5. The cadmium telluride thin-film battery according to claim 4, characterized in that, The first element and the second element are each independently selected from at least one of the elements of the VA group and the IB group.

6. The cadmium telluride thin-film battery according to claim 5, characterized in that, The first element and the second element are each independently selected from at least one of Cu, Ag, N, P, As, and Sb.

7. The method for preparing a cadmium telluride thin-film battery according to any one of claims 1-6, characterized in that, Includes the following steps: (1) After depositing a transparent conductive layer, a high-resistivity layer, a window layer and an absorption layer in sequence on the substrate, the substrate is treated with chlorine to obtain the battery A to be treated; (2) After depositing a first back contact layer on the absorption layer of the battery A to be treated, a first photothermal treatment is performed to obtain the battery B to be treated; (3) After depositing a second back contact layer on the first back contact layer of the battery B to be processed, a second photothermal treatment is performed to form a second back contact layer, and the battery C to be processed is obtained. (4) Deposit a back electrode layer on the second back contact layer of the battery C to be processed; The temperature of the first photothermal treatment is higher than the temperature of the second photothermal treatment.

8. The method for preparing a cadmium telluride thin-film battery according to claim 7, characterized in that, The temperature of the first photothermal treatment is 250℃-450℃, and the time is 1min-60min; And / or, the light intensity of the first photothermal treatment is 0.1-2 standard sunlight.

9. The method for preparing a cadmium telluride thin-film battery according to claim 7, characterized in that, The second photothermal treatment is performed at a temperature of 150℃-400℃ for a time of 1min-60min. And / or, the light intensity of the second photothermal treatment is 0.1-2 standard sunlight.

10. The method for preparing a cadmium telluride thin-film battery according to claim 8 or 9, characterized in that, The light sources for the first photothermal treatment and the second photothermal treatment are each independently selected from at least one of halogen lamps, tungsten lamps, xenon lamps, and LED lamps.

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