Method and apparatus for depositing cadmium tellurium selenide thin films by close space sublimation

Abstract

The application relates to the technical field of photovoltaic cells and discloses a tellurium cadmium selenide film near-space sublimation deposition method and equipment, wherein the tellurium cadmium selenide film near-space sublimation deposition method comprises the following steps: a cadmium selenide heating chamber is used to heat cadmium selenide raw materials, a first gaseous reaction precursor is obtained, the heating temperature is T1, a cadmium telluride heating chamber is used to heat cadmium telluride raw materials, a second gaseous reaction precursor is obtained, the heating temperature is T2, T1>T2 is met, the first gaseous reaction precursor is introduced into a mixing chamber through a first gas outlet pipe, the second gaseous reaction precursor is introduced into the mixing chamber through a second gas outlet pipe, mixed gas is obtained in the mixing chamber, the mixed gas is transported to a nozzle through a connecting pipe, and the nozzle is sprayed towards a substrate, so that a tellurium cadmium selenide film is formed on the surface of the substrate. The cadmium selenide and the cadmium telluride binary alloy are used for near-space sublimation deposition, the stability of the tellurium cadmium selenide film can be remarkably improved, and the photoelectric conversion efficiency of the cell is improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic cell manufacturing technology, specifically to a near-space sublimation deposition method and equipment for cadmium telluride selenide thin films. Background Technology

[0002] Cadmium telluride thin-film batteries have achieved widespread commercial application due to their excellent photoelectric conversion efficiency and low cost per kilowatt-hour. To further improve the photoelectric conversion efficiency of cadmium telluride batteries, a CdSeTe (cadmium telluride selenide) alloy layer can be deposited on the substrate surface to broaden the absorption range of sunlight and passivate defects in the absorption layer.

[0003] In existing technologies, CdSeTe ternary alloys are typically used as raw materials, and near-space sublimation (CSS) deposition processes are employed to prepare CdSeTe thin films. However, due to the differences in saturated vapor pressure and dissociation energy between CdSe (cadmium selenide) and CdTe (cadmium telluride), directly using CdSeTe ternary alloys for CSS deposition can easily lead to instability in the composition of the CdSeTe ternary alloy raw materials, resulting in unstable composition of the deposited CdSeTe thin film. Ultimately, this makes it difficult to improve the photoelectric conversion efficiency of cadmium telluride thin-film solar cells. Summary of the Invention

[0004] In view of this, the present invention provides a near-space sublimation deposition method and apparatus for cadmium telluride selenide thin films to solve the problem that the composition of the CdSeTe thin films prepared by the CSS deposition process using CdSeTe ternary alloy as raw material is unstable, making it difficult to effectively improve the photoelectric conversion efficiency of cadmium telluride thin film batteries.

[0005] In a first aspect, the present invention provides a near-space sublimation deposition method for cadmium telluride selenide thin films, comprising:

[0006] In response to the deposition request, the cadmium selenide raw material was heated in a cadmium selenide heating chamber at a heating temperature of T1 to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide.

[0007] Simultaneously, the cadmium telluride raw material is heated in a cadmium telluride heating chamber at a heating temperature of T2, satisfying T1>T2, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride;

[0008] The first gaseous reaction precursor is introduced into the mixing chamber through the first gas outlet pipe, and the second gaseous reaction precursor is introduced into the mixing chamber through the second gas outlet pipe, so as to obtain a mixed gas in the mixing chamber;

[0009] The mixed gas is transported to the nozzle through a connecting pipe and sprayed onto the substrate to form a cadmium telluride selenide film on the substrate surface.

[0010] Beneficial Effects: The near-space sublimation deposition method for cadmium telluride selenide thin films of the present invention utilizes a cadmium selenide heating chamber to heat the cadmium selenide raw material. The cadmium selenide raw material partially decomposes into gaseous selenium and gaseous cadmium, and partially sublimates into gaseous cadmium selenide, which mixes to form a first gaseous reaction precursor. Simultaneously, a cadmium telluride heating chamber is used to heat the cadmium telluride raw material. The cadmium telluride raw material partially decomposes into gaseous tellurium and gaseous cadmium, and partially sublimates into gaseous cadmium telluride, which mixes to form a second gaseous reaction precursor. The first and second gaseous reaction precursors are then mixed to form a mixed gas, which is then sprayed onto a substrate to form a cadmium telluride selenide thin film on the substrate surface. This achieves the deposition process of a binary alloy of cadmium selenide and cadmium telluride. The cadmium selenide heating chamber and the cadmium telluride heating chamber are isolated from each other and do not interfere with each other, enabling the stable formation of the cadmium telluride selenide thin film on the substrate, significantly improving the stability of the cadmium telluride selenide thin film, thereby contributing to improved photoelectric conversion efficiency of the battery.

[0011] In one optional embodiment, the heating of the cadmium selenide raw material using a cadmium selenide heating chamber at a heating temperature of T1 yields a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide, specifically including:

[0012] The cadmium selenide raw material is dynamically heated in a cadmium selenide heating chamber at a temperature T1, satisfying 630℃≤T1≤700℃, to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas changes dynamically.

[0013] Beneficial effects: By dynamically heating the cadmium selenide raw material using a cadmium selenide heating chamber, the decomposition and sublimation rates of the cadmium selenide raw material can be adjusted by utilizing temperature differences, which in turn adjusts the selenium content in the mixed gas. This results in the formation of a cadmium telluride selenide thin film with a gradually changing selenium content on the substrate surface, achieving a gradual change in the band gap of the cadmium telluride selenide thin film. A gradual change in the band gap is beneficial to improving the collection efficiency of photogenerated carriers, thereby enhancing the photoelectric conversion efficiency of the battery.

[0014] In one optional embodiment, the cadmium selenide raw material is dynamically heated using a cadmium selenide heating chamber at a temperature T1, satisfying 630℃≤T1≤700℃, to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas changes dynamically, specifically including:

[0015] The cadmium selenide raw material is heated in a cadmium selenide heating chamber at a temperature T1, which satisfies 630℃≤T1≤700℃. The heating temperature T1 decreases linearly, resulting in a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas gradually decreases.

[0016] Beneficial effects: By heating cadmium selenide in a cadmium selenide heating chamber and controlling the heating temperature T1 to decrease linearly, the decomposition and sublimation rates of cadmium selenide raw materials can be reduced. This allows the selenium content in the mixed gas to gradually decrease, ultimately resulting in a gradual decrease in the selenium content of the cadmium telluride selenide film in the thickness direction during deposition. This achieves a gradual change in the band gap of the cadmium telluride selenide film, improves the collection efficiency of photogenerated carriers, and thus enhances the photoelectric conversion efficiency of the battery.

[0017] In one optional embodiment, the cadmium telluride raw material is heated in a cadmium telluride heating chamber to a temperature T2, satisfying T1>T2, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. Specifically, this includes:

[0018] The cadmium telluride raw material is dynamically heated in a cadmium telluride heating chamber at a temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas changes dynamically.

[0019] Beneficial effects: By dynamically heating cadmium telluride raw materials using a cadmium telluride heating chamber, the tellurium content in the mixed gas can be adjusted by utilizing temperature differences, thereby indirectly controlling the selenium content in the mixed gas. Similarly, a cadmium telluride selenide thin film with a gradually changing selenium content can be formed on the substrate surface, thereby achieving a gradual change in the band gap of the cadmium telluride selenide thin film, improving the collection efficiency of photogenerated carriers, and thus improving the photoelectric conversion efficiency of the battery.

[0020] In one optional embodiment, the cadmium telluride raw material is dynamically heated using a cadmium telluride heating chamber at a temperature T2, satisfying T1>T2 and 600℃≤T2≤680℃, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas changes dynamically, specifically including:

[0021] The cadmium telluride raw material is heated in a cadmium telluride heating chamber at a temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃. The heating temperature T2 increases linearly, resulting in a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas gradually decreases.

[0022] Beneficial effects: Heating cadmium telluride raw materials using a cadmium telluride heating chamber and controlling the heating temperature T2 to increase linearly can improve the decomposition and sublimation rates of cadmium telluride raw materials, indirectly reducing the selenium content in the mixed gas. Ultimately, this results in a gradual decrease in the selenium content of the cadmium telluride selenide film in the thickness direction during deposition, achieving a gradual change in the band gap of the cadmium telluride selenide film, improving the collection efficiency of photogenerated carriers, and thus enhancing the photoelectric conversion efficiency of the battery.

[0023] In one optional embodiment, the step of conveying the mixed gas to the nozzle via a connecting pipe and spraying it onto the substrate through the nozzle to form a cadmium telluride selenide film on the substrate surface specifically includes:

[0024] In the negative pressure chamber, the mixed gas is transported to the nozzle through a connecting pipe and sprayed onto the substrate to form a cadmium telluride selenide film on the substrate surface. The selenium content in the cadmium telluride selenide film gradually decreases in the thickness direction.

[0025] Beneficial effects: Preparing cadmium telluride selenide (CDS) films in a negative pressure chamber can prevent the oxidation of Cd, Se, and Te, and reduce the incorporation of impurities into the CDS film. The selenium content in the CDS film gradually decreases along the thickness direction, enabling a gradual change in the band gap of the CDS film, improving the collection efficiency of photogenerated carriers, and thus enhancing the photoelectric conversion efficiency of the battery.

[0026] In one optional embodiment, the pressure in the negative pressure chamber is P, which satisfies 0.1 Torr ≤ P ≤ 20 Torr.

[0027] Beneficial effects: By controlling the pressure in the negative pressure chamber, the oxidation of Cd, Se, and Te can be further avoided, thus improving the processing quality of cadmium selenide telluride films.

[0028] In one alternative implementation, it further includes:

[0029] The temperature T3 of the substrate is controlled within the range of 500℃≤T3≤600℃.

[0030] Beneficial effects: By controlling the temperature of the substrate, the high-temperature mixed gas can quickly accumulate on the surface of the substrate and form a cadmium telluride selenide film when it encounters the relatively low-temperature substrate, which helps to further improve the process stability of the cadmium telluride selenide film.

[0031] Secondly, the present invention also provides a near-space sublimation deposition apparatus for cadmium telluride selenide thin films, comprising: an apparatus body, wherein a negative pressure chamber is provided within the apparatus body, and a cadmium selenide heating chamber, a cadmium telluride heating chamber, and a mixing chamber are provided at intervals within the negative pressure chamber, a first vent pipe is provided at the top of the cadmium selenide heating chamber, and a second vent pipe is provided at the top of the cadmium telluride heating chamber, the first vent pipe and the second vent pipe are respectively connected to the mixing chamber, and a connecting pipe is also provided within the negative pressure chamber, one end of the connecting pipe being connected to the mixing chamber, and a nozzle being provided at the opposite end, the nozzle being adapted to spray a mixed gas onto a substrate and form a cadmium telluride selenide thin film on the substrate.

[0032] Beneficial Effects: The near-space sublimation deposition apparatus for cadmium telluride selenide thin films of the present invention utilizes a cadmium selenide heating chamber to heat the cadmium selenide raw material. Part of the cadmium selenide raw material decomposes into gaseous selenium and gaseous cadmium, while the remainder sublimates into gaseous cadmium selenide, which mixes to form a first gaseous reaction precursor. Simultaneously, a cadmium telluride heating chamber is used to heat the cadmium telluride raw material. Part of the cadmium telluride raw material decomposes into gaseous tellurium and gaseous cadmium, while the remainder sublimates into gaseous cadmium telluride, which mixes to form a second gaseous reaction precursor. The first and second gaseous reaction precursors are then mixed to form a mixed gas, which is then sprayed onto a substrate to form a cadmium telluride selenide thin film on the substrate surface. This achieves the deposition process of a binary alloy of cadmium selenide and cadmium telluride. The cadmium selenide heating chamber and the cadmium telluride heating chamber are isolated from each other and do not interfere with each other, enabling the stable formation of the cadmium telluride selenide thin film on the substrate, significantly improving the stability of the cadmium telluride selenide thin film, thereby contributing to improved photoelectric conversion efficiency of the battery.

[0033] In one optional embodiment, the cadmium selenide heating chamber and the cadmium telluride heating chamber are respectively provided with heat insulation layers on the periphery of their chamber walls;

[0034] The length of the first vent pipe is L1, which satisfies L1≥50 mm, and the length of the second vent pipe is L2, which satisfies L2≥50 mm.

[0035] Beneficial effects: By setting heat insulation layers on the periphery of the walls of the cadmium selenide heating chamber and the cadmium telluride heating chamber respectively, and ensuring that the lengths of the first and second exhaust pipes are sufficiently long, the temperature interference between the cadmium selenide heating chamber and the cadmium telluride heating chamber can be avoided, and the temperature of the cadmium selenide heating chamber and the cadmium telluride heating chamber can be independently controlled. Attached Figure Description

[0036] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0037] Figure 1 This is a schematic flowchart of a near-space sublimation deposition method for cadmium telluride selenide thin films according to an embodiment of the present invention.

[0038] Figure 2 This is a schematic diagram of a near-space sublimation deposition apparatus for cadmium telluride selenide thin films according to an embodiment of the present invention;

[0039] Figure 3 This is a graph showing the change in selenium concentration in a cadmium telluride thin film as a function of deposition cycles in a near-space sublimation deposition method for cadmium telluride thin films according to an embodiment of the present invention.

[0040] Figure 4 This is a graph showing the variation of selenium concentration in a cadmium telluride thin film with its thickness, according to a near-space sublimation deposition method for cadmium telluride thin films in an embodiment of the present invention.

[0041] Explanation of reference numerals in the attached figures:

[0042] 1. Equipment body; 101. Negative pressure chamber; 102. Cadmium selenide heating chamber; 103. Cadmium telluride heating chamber; 104. Mixing chamber; 105. First exhaust pipe; 106. Second exhaust pipe; 107. Connecting pipe; 108. Nozzle; 2. Substrate; 3. Cadmium telluride selenide thin film; 4. Cadmium selenide raw material; 5. Cadmium telluride raw material. Detailed Implementation

[0043] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0044] The following is combined Figures 1 to 2 The following describes embodiments of the present invention.

[0045] According to embodiments of the present invention, in one aspect, such as Figure 1 As shown, a near-space sublimation deposition method for cadmium telluride selenide thin films is provided, comprising:

[0046] S100, in response to the deposition request, the cadmium selenide raw material 4 is heated in the cadmium selenide heating chamber 102 at a heating temperature of T1 to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide.

[0047] S200 Simultaneously, the cadmium telluride raw material 5 is heated using the cadmium telluride heating chamber 103 at a heating temperature of T2, satisfying T1>T2, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride.

[0048] S300, the first gaseous reaction precursor is introduced into the mixing chamber 104 through the first gas outlet pipe 105, and the second gaseous reaction precursor is introduced into the mixing chamber 104 through the second gas outlet pipe 106, so as to obtain a mixed gas in the mixing chamber 104.

[0049] S400, the mixed gas is transported to the nozzle 108 through the connecting pipe 107 and sprayed onto the substrate 2 through the nozzle 108 to form a cadmium telluride selenide thin film 3 on the surface of the substrate 2.

[0050] Therefore, the near-space sublimation deposition method for cadmium telluride selenide thin films provided in this embodiment of the invention utilizes a cadmium selenide heating chamber 102 to heat the cadmium selenide raw material 4. The cadmium selenide raw material 4 partially decomposes into gaseous selenium and gaseous cadmium, and partially sublimates into gaseous cadmium selenide, which mixes to form a first gaseous reaction precursor. Simultaneously, a cadmium telluride heating chamber 103 is used to heat the cadmium telluride raw material 5. The cadmium telluride raw material 5 partially decomposes into gaseous tellurium and gaseous cadmium, and partially sublimates into gaseous cadmium telluride, which mixes to form a second gaseous reaction precursor. Then, the first gaseous reaction precursor and the second gaseous reaction precursor are mixed to form a mixed gas, which is then sprayed onto the substrate 2 to form a cadmium telluride selenide thin film 3 on the surface of the substrate 2. This realizes the deposition process of cadmium selenide and cadmium telluride binary alloy. The cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 are isolated from each other and do not affect each other. The cadmium telluride selenide thin film 3 can be stably formed on the substrate 2, which significantly improves the stability of the cadmium telluride thin film 3, thereby helping to improve the photoelectric conversion efficiency of the battery.

[0051] Specifically, the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 are independently controlled and have different heating temperatures. In the cadmium selenide heating chamber 102, the cadmium selenide raw material 4, at a heating temperature T1, partially decomposes into gaseous selenium and gaseous cadmium, and partially sublimates into gaseous cadmium selenide, forming a first gaseous reaction precursor consisting of a mixture of gaseous selenium, gaseous cadmium, and gaseous cadmium selenide. In the cadmium telluride heating chamber 103, the cadmium telluride raw material 5, at a heating temperature T2, partially decomposes into gaseous tellurium and gaseous cadmium, and partially sublimates into gaseous cadmium telluride, forming a second gaseous reaction precursor consisting of a mixture of gaseous tellurium, gaseous cadmium, and gaseous cadmium telluride. After the first and second gaseous reaction precursors are mixed in the mixing chamber 104, a mixed gas consisting of gaseous selenium, gaseous tellurium, gaseous cadmium, gaseous cadmium selenide, and gaseous cadmium telluride is formed.

[0052] In addition, the substrate 2 can be a transparent conductive glass substrate, and the thickness of the cadmium telluride thin film 3 is about 1 μm to 2 μm.

[0053] Compared to traditional single CdSeTe sources, the cadmium telluride selenide (CdSeTe, abbreviated as CST) films prepared in the embodiments of the present invention have relatively stable components.

[0054] At the same temperature, the vapor pressure of cadmium selenide (CdSe) is significantly lower than that of cadmium telluride (CdTe). If both are heated to the same temperature, the vapor of CdTe will dominate the deposition process, resulting in an excessively high Te content in the CdSeTe film, making it difficult to form the desired CdSeTe film. In this embodiment of the invention, controlling the heating temperature T1 of the cadmium selenide heating chamber 102 to be greater than the heating temperature T2 of the cadmium telluride heating chamber 103 can increase the vapor pressure of CdSe, matching the supply of Cd and Se with the supply of Cd and Te, thereby achieving controllable Se and Te content in the CdSeTe film.

[0055] In one embodiment, in step S100, the cadmium selenide raw material 4 is heated using the cadmium selenide heating chamber 102 at a heating temperature of T1 to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide, specifically including:

[0056] S110. Cadmium selenide raw material 4 is dynamically heated using cadmium selenide heating chamber 102 at a temperature of T1, satisfying 630℃≤T1≤700℃. This yields a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas changes dynamically. The content of gaseous selenium refers to the ratio of the amount of gaseous selenium per unit volume to the total amount of gas in the mixed gas. Dynamic heating refers to the change of the heating temperature T1 of cadmium selenide heating chamber 102 over time.

[0057] By dynamically heating the cadmium selenide raw material 4 using the cadmium selenide heating chamber 102, the decomposition rate and sublimation rate of the cadmium selenide raw material 4 can be adjusted by utilizing the temperature difference, that is, the selenium content in the mixed gas can be adjusted, thereby forming a cadmium telluride selenide thin film 3 with a gradually changing selenium content on the surface of the substrate 2. This achieves a gradual change in the band gap of the cadmium telluride selenide thin film 3, which is beneficial to improving the collection efficiency of photogenerated carriers, thereby improving the photoelectric conversion efficiency of the battery.

[0058] Specifically, by installing heaters in the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 respectively, dynamic control of the heating temperature in the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 can be achieved. The heaters can be heating wires, heating lamps, etc., and the specific settings can be selected according to actual needs.

[0059] Further, in one embodiment, in step S110, the cadmium selenide raw material 4 is dynamically heated using the cadmium selenide heating chamber 102 at a heating temperature of T1, satisfying 630℃≤T1≤700℃, to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The dynamic change in the content of gaseous selenium in the mixed gas specifically includes:

[0060] S1110. Cadmium selenide raw material 4 is heated in cadmium selenide heating chamber 102 at a heating temperature of T1, which satisfies 630℃≤T1≤700℃. The heating temperature T1 decreases linearly, resulting in a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas gradually decreases.

[0061] For example, the total deposition time for a single substrate 2 is 60 seconds, during which the heating temperature T1 in the cadmium selenide heating chamber 102 is controlled to decrease linearly from 700°C to 660°C. Linear decrease means that the temperature decreases uniformly over time.

[0062] The cadmium selenide raw material 4 is heated by the cadmium selenide heating chamber 102, and the heating temperature T1 is controlled to decrease linearly. This reduces the decomposition rate and sublimation rate of the cadmium selenide raw material 4, thereby controlling the selenium content in the mixed gas to gradually decrease. Ultimately, this results in a gradual decrease in the selenium content of the cadmium telluride selenide film 3 in the thickness direction during the deposition process, achieving a gradual change in the band gap of the cadmium telluride selenide film 3, improving the photogenerated carrier collection efficiency, and thus enhancing the photoelectric conversion efficiency of the battery.

[0063] In one embodiment, in step S200, the cadmium telluride raw material 5 is heated using the cadmium telluride heating chamber 103 to a heating temperature of T2, satisfying T1>T2, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride, specifically including:

[0064] S210. Cadmium telluride raw material 5 is dynamically heated using cadmium telluride heating chamber 103. The heating temperature is T2, which satisfies T1>T2 and 600℃≤T2≤680℃. A second gaseous reaction precursor is obtained, consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas changes dynamically.

[0065] By dynamically heating cadmium telluride in the heating chamber 103, the content of tellurium in the mixed gas can be adjusted by the temperature difference, thereby indirectly controlling the content of selenium in the mixed gas. Similarly, a cadmium telluride selenide thin film 3 with a gradually changing selenium content can be formed on the surface of the substrate 2, thereby achieving a gradual change in the band gap of the cadmium telluride selenide thin film 3, improving the collection efficiency of photogenerated carriers, and thus improving the photoelectric conversion efficiency of the battery.

[0066] Further, in one embodiment, in step S210, the cadmium telluride raw material 5 is dynamically heated using the cadmium telluride heating chamber 103 at a heating temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The dynamic change in the content of gaseous selenium in the mixed gas specifically includes:

[0067] S2110. Cadmium telluride raw material 5 is heated in cadmium telluride heating chamber 103 at a heating temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃. The heating temperature T2 increases linearly, resulting in a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas gradually decreases.

[0068] By heating the cadmium telluride raw material 5 in the cadmium telluride heating chamber 103 and controlling the heating temperature T2 to increase linearly, the decomposition rate and sublimation rate of the cadmium telluride raw material 5 can be improved, indirectly reducing the selenium content in the mixed gas. Ultimately, the selenium content of the cadmium telluride selenide film 3 gradually decreases in the thickness direction during the deposition process, achieving a gradual change in the band gap of the cadmium telluride selenide film 3, improving the photogenerated carrier collection efficiency, and thus improving the photoelectric conversion efficiency of the battery.

[0069] In one embodiment, in step 400, the mixed gas is delivered to the nozzle 108 via the connecting pipe 107 and sprayed onto the substrate 2 through the nozzle 108 to form a cadmium telluride selenide thin film 3 on the surface of the substrate 2, specifically including:

[0070] S410. In the negative pressure chamber 101, the mixed gas is transported to the nozzle 108 through the connecting pipe 107 and sprayed onto the substrate 2 through the nozzle 108 to form a cadmium telluride selenide film 3 on the surface of the substrate 2. The selenium content in the cadmium telluride selenide film 3 gradually decreases in the thickness direction.

[0071] The preparation of cadmium telluride selenide thin film 3 within the negative pressure chamber 101 can prevent the oxidation of Cd, Se, and Te, and reduce the incorporation of impurities into the cadmium telluride selenide thin film 3. The selenium content in the cadmium telluride selenide thin film 3 gradually decreases in the thickness direction, which can achieve a gradual change in the band gap of the cadmium telluride selenide thin film 3, improve the collection efficiency of photogenerated carriers, and thus improve the photoelectric conversion efficiency of the battery.

[0072] Furthermore, in one embodiment, the pressure of the negative pressure chamber 101 is P, satisfying 0.1 Torr ≤ P ≤ 20 Torr. By controlling the pressure of the negative pressure chamber 101, the oxidation of Cd, Se, and Te can be further avoided, thereby improving the processing quality of the cadmium telluride selenide film 3.

[0073] For example, in this embodiment of the invention, the pressure P of the negative pressure chamber 101 can be 0.1 Torr, 2 Torr, 4 Torr, 8 Torr, 12 Torr, 16 Torr, 20 Torr, etc.

[0074] In one embodiment, the near-space sublimation deposition method for cadmium telluride selenide thin films further includes:

[0075] S500, the temperature T3 of the substrate 2 is controlled within the range of 500℃≤T3≤600℃. By controlling the temperature of the substrate 2, the high-temperature mixed gas can quickly accumulate on the surface of the substrate 2 and form a cadmium telluride selenide thin film 3 after encountering the relatively low-temperature substrate 2, which is beneficial to further improve the process stability of the cadmium telluride thin film 3.

[0076] For example, in this embodiment of the invention, the temperature T3 of the substrate 2 can be 500°C, 520°C, 540°C, 560°C, 580°C, 600°C, etc.

[0077] The near-space sublimation deposition method of cadmium telluride selenide thin film according to the present invention will be described in further detail below with reference to specific embodiments. These examples should not be construed as limiting the scope of protection claimed by the present invention.

[0078] Example 1:

[0079] The pressure P in the negative pressure chamber 101 is controlled at 8 Torr, and the temperature T3 of the substrate 2 is 560°C. Cadmium selenide raw material 4 is heated at a constant temperature T1 of 700°C using the cadmium selenide heating chamber 102, yielding a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. Simultaneously, cadmium telluride raw material 5 is heated at a constant temperature T2 of 660°C using the cadmium telluride heating chamber 103, yielding a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The first gaseous reaction precursor is introduced into the mixing chamber 104 via the first vent pipe 105, and the second gaseous reaction precursor is introduced into the mixing chamber 104 via the second vent pipe 106, resulting in a mixed gas within the mixing chamber 104. The mixed gas is transported to the nozzle 108 through the connecting pipe 107 and sprayed onto the substrate 2 through the nozzle 108 to form a CdSeTe thin film, also known as a CST film, on the surface of the substrate 2.

[0080] Example 2:

[0081] The pressure P in the negative pressure chamber 101 is controlled at 8 Torr, and the temperature T3 of the substrate 2 is 560°C. Cadmium selenide raw material 4 is dynamically heated using the cadmium selenide heating chamber 102, with the heating temperature T1 linearly decreasing from 700°C to 660°C, yielding a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. Simultaneously, cadmium telluride raw material 5 is dynamically heated using the cadmium telluride heating chamber 103, with the heating temperature T2 linearly increasing from 600°C to 650°C, yielding a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The first gaseous reaction precursor is introduced into the mixing chamber 104 via the first vent pipe 105, and the second gaseous reaction precursor is introduced into the mixing chamber 104 via the second vent pipe 106, resulting in a mixed gas within the mixing chamber 104. The mixed gas is transported to the nozzle 108 through the connecting pipe 107 and sprayed onto the substrate 2 through the nozzle 108 to form a CdSeTe thin film, also known as a CST film, on the surface of the substrate 2.

[0082] Control group:

[0083] A traditional CdSeTe ternary alloy was used as the raw material for CSS deposition. The CdSeTe ternary alloy was heated at a constant temperature of 660°C. The temperature T3 of the substrate 2 was 560°C, and the pressure P in the negative pressure chamber 101 was 8 Torr. The gaseous reaction precursor formed by the high-temperature sublimation of the CdSeTe ternary alloy formed a CdSeTe thin film, also known as a CST film, on the substrate 2.

[0084] Depend on Figure 3 It can be seen that during the long deposition process, the Se concentration of the CdSeTe film prepared using Example 1 of the present invention remains basically unchanged, which significantly improves the preparation stability of the CdSeTe film. In contrast, the Se concentration of the CdSeTe film prepared using the control group gradually decreases with the increase of deposition times. The Se concentration of the CdSeTe film prepared on the subsequent substrate 2 is too low, resulting in a low photoelectric conversion efficiency of the battery.

[0085] It should be noted that a single substrate 2 only requires one deposition of the CdSeTe thin film; the increase in the number of depositions mentioned above applies to multiple substrates 2. The formula for calculating the Se concentration is as follows: Se / (Se+Te), where Se and Te are relative atomic ratios. The Se concentration can be measured using conventional detection equipment such as energy dispersive spectroscopy (EDS), secondary ion mass spectrometry (SIMS), and X-ray photoelectron spectroscopy (XPS).

[0086] Depend on Figure 4 It can be seen that the CdSeTe film prepared using Example 1 of the present invention forms a gradient of Se concentration along the thickness direction, which is beneficial to improving the photogenerated carrier collection efficiency and photoelectric conversion efficiency of the battery. The CdSeTe film prepared using the control group has a basically constant Se concentration along the thickness direction, resulting in poor photoelectric conversion efficiency of the battery.

[0087] According to an embodiment of the present invention, on the other hand, such as Figure 2 As shown, a near-space sublimation deposition apparatus for cadmium telluride selenide thin films is also provided, comprising: an apparatus body 1, a negative pressure chamber 101 provided inside the apparatus body 1, a cadmium selenide heating chamber 102, a cadmium telluride heating chamber 103 and a mixing chamber 104 spaced apart inside the negative pressure chamber 101, a first vent pipe 105 provided at the top of the cadmium selenide heating chamber 102, a second vent pipe 106 provided at the top of the cadmium telluride heating chamber 103, the first vent pipe 105 and the second vent pipe 106 respectively communicating with the mixing chamber 104, a connecting pipe 107 provided inside the negative pressure chamber 101, one end of the connecting pipe 107 being connected to the mixing chamber 104, and a nozzle 108 provided at the opposite end, the nozzle 108 being adapted to spray mixed gas onto a substrate 2 and form a cadmium telluride selenide thin film 3 on the substrate 2.

[0088] The near-space sublimation deposition apparatus for cadmium telluride selenide thin films of the present invention utilizes a cadmium selenide heating chamber 102 to heat cadmium selenide raw material 4, causing partial decomposition of cadmium selenide raw material 4 into gaseous selenium and gaseous cadmium, and partial sublimation into gaseous cadmium selenide, which mix to form a first gaseous reaction precursor. Simultaneously, a cadmium telluride heating chamber 103 is used to heat cadmium telluride raw material 5, causing partial decomposition of cadmium telluride and gaseous cadmium, and partial sublimation into gaseous cadmium telluride, which mix to form a second gaseous reaction precursor. Then, the first gaseous reaction precursor and the second gaseous reaction precursor are mixed to form a mixed gas, which is then sprayed onto the substrate 2 to form a cadmium telluride selenide thin film 3 on the surface of the substrate 2. This realizes the deposition process of cadmium selenide and cadmium telluride binary alloy. The cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 are isolated from each other and do not affect each other. The cadmium telluride selenide thin film 3 can be stably formed on the substrate 2, which significantly improves the stability of the cadmium telluride thin film 3, thereby helping to improve the photoelectric conversion efficiency of the battery.

[0089] In one embodiment, such as Figure 2 As shown, heat insulation layers are respectively provided on the periphery of the walls of the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103. The length of the first vent pipe 105 is L1, satisfying L1≥50 mm, and the length of the second vent pipe 106 is L2, satisfying L2≥50 mm. By providing heat insulation layers on the periphery of the walls of the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103, and by setting appropriate lengths for the first vent pipe 105 and the second vent pipe 106, mutual temperature interference between the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 can be avoided, and independent temperature control of the cadmium selenide heating chamber 102 and the cadmium telluride heating chamber 103 can be achieved.

[0090] For example, such as Figure 2 As shown, the first vent pipe 105 extends vertically upward, with a length L1 of 50 mm. The second vent pipe 106 extends vertically upward, with a length L2 of 50 mm.

[0091] To achieve the basic functions of the cadmium telluride selenide thin film near-space sublimation deposition apparatus, the apparatus in this embodiment may further include other necessary modules or components, such as a housing and a control system. It should be noted that the other necessary modules or components included in the cadmium telluride selenide thin film near-space sublimation deposition apparatus can be any suitable existing structure. To clearly and concisely illustrate the technical solution provided in this embodiment, the above-mentioned parts will not be repeated here, and the accompanying drawings have also been simplified accordingly. However, it should be understood that the scope of the embodiments of the present invention is not limited thereto.

[0092] Although embodiments of the invention have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of the invention, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A near-space sublimation deposition method for cadmium telluride selenide thin films, characterized in that, include: In response to the deposition request, the cadmium selenide raw material (4) is heated in the cadmium selenide heating chamber (102) at a heating temperature of T1 to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium and a mixture of gaseous cadmium selenide. Meanwhile, the cadmium telluride raw material (5) is heated in the cadmium telluride heating chamber (103) at a heating temperature of T2, satisfying T1>T2, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride; The first gaseous reaction precursor is introduced into the mixing chamber (104) through the first gas outlet pipe (105), and the second gaseous reaction precursor is introduced into the mixing chamber (104) through the second gas outlet pipe (106), so that a mixed gas is obtained in the mixing chamber (104); The mixed gas is transported to the nozzle (108) through the connecting pipe (107) and sprayed onto the substrate (2) through the nozzle (108) to form a cadmium telluride selenide film (3) on the surface of the substrate (2).

2. The near-space sublimation deposition method for cadmium telluride selenide thin films according to claim 1, characterized in that, The process involves heating the cadmium selenide raw material (4) in a cadmium selenide heating chamber (102) at a temperature of T1 to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. Specifically, this includes: The cadmium selenide raw material (4) is dynamically heated using a cadmium selenide heating chamber (102) at a temperature of T1, satisfying 630℃≤T1≤700℃, to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas changes dynamically.

3. The near-space sublimation deposition method for cadmium telluride selenide thin films according to claim 2, characterized in that, The cadmium selenide raw material (4) is dynamically heated using a cadmium selenide heating chamber (102) at a temperature of T1, satisfying 630℃≤T1≤700℃, to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas changes dynamically, specifically including: The cadmium selenide raw material (4) is heated in a cadmium selenide heating chamber (102) at a temperature of T1, which satisfies 630℃≤T1≤700℃. The heating temperature T1 decreases linearly to obtain a first gaseous reaction precursor consisting of gaseous selenium, gaseous cadmium, and a mixture of gaseous cadmium selenide. The content of gaseous selenium in the mixed gas gradually decreases.

4. The near-space sublimation deposition method for cadmium telluride selenide thin films according to claim 1, characterized in that, The cadmium telluride raw material (5) is heated in a cadmium telluride heating chamber (103) at a temperature of T2, satisfying T1>T2, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride, specifically including: The cadmium telluride raw material (5) is dynamically heated using a cadmium telluride heating chamber (103) at a heating temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas changes dynamically.

5. The near-space sublimation deposition method for cadmium telluride selenide thin films according to claim 4, characterized in that, The cadmium telluride raw material (5) is dynamically heated using a cadmium telluride heating chamber (103) at a temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃, to obtain a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas changes dynamically, specifically including: The cadmium telluride raw material (5) is heated in a cadmium telluride heating chamber (103) at a temperature of T2, satisfying T1>T2 and 600℃≤T2≤680℃. The heating temperature T2 increases linearly, resulting in a second gaseous reaction precursor consisting of gaseous tellurium, gaseous cadmium, and a mixture of gaseous cadmium telluride. The content of gaseous selenium in the mixed gas gradually decreases.

6. The near-space sublimation deposition method for cadmium telluride selenide thin films according to any one of claims 2 to 5, characterized in that, The process of using a connecting pipe (107) to transport the mixed gas to a nozzle (108) and spraying it onto the substrate (2) through the nozzle (108) to form a cadmium telluride selenide film (3) on the surface of the substrate (2) specifically includes: Inside the negative pressure chamber (101), the mixed gas is transported to the nozzle (108) via the connecting pipe (107) and sprayed onto the substrate (2) through the nozzle (108) to form a cadmium telluride selenide film (3) on the surface of the substrate (2). The selenium content in the cadmium telluride selenide film (3) gradually decreases in the thickness direction.

7. The near-space sublimation deposition method for cadmium telluride selenide thin films according to claim 6, characterized in that, The pressure in the negative pressure chamber (101) is P, which satisfies 0.1 Torr ≤ P ≤ 20 Torr.

8. The near-space sublimation deposition method for cadmium telluride selenide thin films according to any one of claims 2 to 5, characterized in that, Also includes: The temperature T3 of the substrate (2) is controlled within the range of 500℃≤T3≤600℃.

9. A near-space sublimation deposition apparatus for cadmium telluride selenide thin films, characterized in that, include: The device body (1) is provided with a negative pressure chamber (101). The negative pressure chamber (101) is provided with a cadmium selenide heating chamber (102), a cadmium telluride heating chamber (103) and a mixing chamber (104) spaced apart. The top of the cadmium selenide heating chamber (102) is provided with a first vent pipe (105), and the top of the cadmium telluride heating chamber (103) is provided with a second vent pipe (106). The first vent pipe (105) and the second vent pipe (106) are respectively connected to the mixing chamber (104). The negative pressure chamber (101) is also provided with a connecting pipe (107). One end of the connecting pipe (107) is connected to the mixing chamber (104), and the other end is provided with a nozzle (108). The nozzle (108) is adapted to spray mixed gas onto the substrate (2) and form a cadmium telluride selenide film (3) on the substrate (2).

10. The near-space sublimation deposition apparatus for cadmium telluride selenide thin films according to claim 9, characterized in that, The cadmium selenide heating chamber (102) and the cadmium telluride heating chamber (103) are respectively provided with heat insulation layers on the periphery of the chamber walls; The length of the first vent pipe (105) is L1, which satisfies L1≥50 mm, and the length of the second vent pipe (106) is L2, which satisfies L2≥50 mm.

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