Infrared radiation light back contact thermophotovoltaic device structure and preparation process
By fabricating back-contact thermal photovoltaic devices on germanium wafers, the problems of high cost and low absorption coefficient in existing technologies have been solved, achieving efficient infrared radiation photoelectric conversion and improving the photoelectric conversion performance of the devices.
Patent Information
- Application Number
- CN202511555439.5
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-10-29
- Publication Date
- 2026-01-23
AI Technical Summary
Existing thermophotovoltaic cell manufacturing processes are costly, and germanium has a low absorption coefficient when used as a photon absorber, making it difficult to achieve efficient conversion of infrared radiation into electrical energy.
A back-contact thermal photovoltaic device structure is adopted. Boron diffusion is performed on the germanium wafer to form a P+ front field, N-region and P-region are etched to form a phosphorus-doped nanocrystalline silicon thin film and a stacked film to form a back metal electrode, avoiding the front electrode from blocking and optimizing carrier collection.
It improves the photoelectric conversion efficiency of infrared radiation, reduces the resistance of the contact area, and enhances the overall photoelectric conversion efficiency of thermal radiation.
Smart Images
Figure CN121398209A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermophotovoltaic power generation, specifically to a back-contact thermophotovoltaic device structure and fabrication process for infrared radiation light. Background Technology
[0002] Thermophotovoltaics (TPV) technology converts radiant heat into electrical energy by emitting photons that are incident on photovoltaic cells. Given that TPV systems can use a variety of heat sources to fuel them, TPV technology has many potential applications, such as: combined heat and power in residential applications, power generation in spacecraft, electricity from thermal energy storage systems, waste heat recovery in heavy industrial processes, and waste heat recovery from photovoltaic systems to reduce photovoltaic module temperature, improve photovoltaic module power generation efficiency, and mitigate the risks of high temperatures.
[0003] One of the main challenges of TPV is developing high-efficiency cells with cost-effective manufacturing processes. Record-breaking efficiencies can be achieved using low-bandgap III-V semiconductor compounds, most of which are epitaxially grown on InP substrates. A viable alternative to this approach includes utilizing crystalline germanium (E-gap = 0.67 eV) as a photon absorber.
[0004] Although germanium is an indirect bandgap semiconductor with a lower absorption coefficient compared to other low bandgap materials such as InGaAs, its benefits for TPV systems primarily stem from cost. Firstly, germanium wafers are cheaper than InP. Secondly, expensive epitaxial technologies can be avoided because germanium, as a group IV material, is highly compatible with silicon technology, allowing for thin-film deposition techniques such as PECVD and ALD, which are standard methods in the silicon solar cell industry.
[0005] Therefore, despite its inherent limitations, germanium-based technology is a microcosm of a cost-effective strategy for developing TPV batteries with viable prospects for industrial scalability. Summary of the Invention
[0006] To address the shortcomings of existing technologies, this invention proposes a back-contact thermal photovoltaic device structure and fabrication process for infrared radiation light.
[0007] The objective of this invention can be achieved through the following technical solutions:
[0008] A first aspect of the present invention relates to a fabrication process for a back-contact thermal photovoltaic device, comprising the following steps:
[0009] Boron diffusion is performed on a P-type substrate to form a P+ front field;
[0010] Etch the P+ front field on the back side of the substrate to reserve the formation area of the N region;
[0011] A phosphorus-doped nanocrystalline silicon thin film layer is deposited on the back side of the substrate;
[0012] A multilayer film is deposited on the back or both sides of the substrate to form a stacked film;
[0013] The mold is partially opened in the P-region and the N-region, wherein the mold opening in the P-region includes opening the stacked film and the phosphorus-doped nanocrystalline silicon thin film layer below it; the mold opening in the N-region includes opening the stacked film.
[0014] A metal film is deposited on the back to form the positive and negative electrodes; patterning is performed to isolate the metal film on the positive electrode from the metal film on the negative electrode.
[0015] Optionally, the boron diffusion process conditions are as follows: boron diffusion is carried out in a temperature range of 900°C to 1050°C; the gas source is boron trichloride.
[0016] Optionally, the thickness of the phosphorus-doped nanocrystalline silicon thin film is controlled to be between 1 and 5 nm, and the doping concentration ranges from [missing value]. .
[0017] Optionally, the substrate is a P-type germanium wafer; the metal film is an aluminum film or an aluminum-silicon film.
[0018] Optionally, the phosphorus-doped nanocrystalline silicon thin film layer is formed by PECVD or PVD deposition; the stacked film is formed by PECVD, ALD, or PVD deposition; the stacked film is a-SiC. x / Al2O3 / SiC stacked film.
[0019] Optionally, the metal film is formed by vapor deposition or magnetron sputtering; the etching in the P+ front field of the etched substrate back side portion is laser etching or mask etching; the patterning includes printed etching.
[0020] A second aspect of the present invention relates to a back-contact thermal photovoltaic device, comprising:
[0021] P-type substrate;
[0022] P+ front field formed on the front side of a P-type substrate;
[0023] A P-region contact structure disposed on the back side of a substrate includes a phosphorus-doped nanocrystalline silicon thin film layer, a stacked film, and a metal electrode A that passes through the stacked film and the phosphorus-doped nanocrystalline silicon thin film layer and is in contact with the substrate.
[0024] And, the N-region contact structure disposed on the back side of the substrate includes a phosphorus-doped nanocrystalline silicon thin film layer formed on the back side of the substrate, a stacked film, and a metal electrode B passing through the stacked film and in contact with the phosphorus-doped nanocrystalline silicon thin film layer.
[0025] Metal electrode A and metal electrode B are isolated from each other.
[0026] Optionally, the substrate is a P-type germanium sheet; the metal electrode A and / or metal electrode B are aluminum films or aluminum-silicon films.
[0027] Optionally, a multilayer film, which is a-SiC, is also deposited on the front P+ field of the substrate. x / Al2O3 / SiC.
[0028] A third aspect of the present invention relates to a photovoltaic device, comprising a device prepared by the aforementioned back-contact thermal photovoltaic device manufacturing process or the aforementioned back-contact thermal photovoltaic device.
[0029] The beneficial effects of this invention are:
[0030] The back-contact thermophotovoltaic device of the present invention has no electrode obstruction on the front side, which increases the light received on the front side and improves the photoelectric conversion efficiency of infrared radiation on the front side; in addition, a p+ front field is added on the front side and a p+ layer is added to the P-region metal contact area on the back side, which improves the collection efficiency of photogenerated carriers, reduces the contact area resistance, and improves the overall photoelectric conversion efficiency of the device. Attached Figure Description
[0031] The invention will now be further described with reference to the accompanying drawings.
[0032] Figure 1 This is a process flow diagram for this application;
[0033] Figure 2 This is a schematic diagram of the device structure obtained using the process described in this application. Detailed Implementation
[0034] 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, and 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.
[0035] like Figure 1 As shown, in some embodiments of the present invention, a fabrication process for a back-contact thermal photovoltaic device is disclosed, which may include the following steps:
[0036] Step 1: Preparation and double-sided polishing of P-type germanium (Ge) wafers
[0037] P-type germanium wafers with a resistivity ranging from 0.1 to 5 Ω·cm were selected as the substrate material. The germanium wafers were subjected to double-sided polishing to ensure the optical and physical quality of the substrate surface.
[0038] For example, double-sided polishing can include mechanical polishing and / or chemical polishing. In some examples, chemical polishing may include the following steps: immersing a germanium sheet in a NaOH or KOH aqueous solution prepared with deionized water until sufficient material is uniformly removed from both sides of the germanium sheet to achieve a double-sided polishing effect. The germanium sheet is then removed from the polishing solution and rinsed with deionized water to thoroughly remove any residual alkali and reaction byproducts. Finally, it is dried using methods such as nitrogen blowing or centrifugal drying.
[0039] Step 2: High-temperature boron diffusion forms the P+ front field
[0040] The polished germanium wafers are placed in the center of a tube furnace. Boron diffusion treatment is then performed, with the diffusion temperature controlled within the range of 900°C to 1050°C. Boron trichloride (BCH) is used as the diffusion gas source. ).
[0041] This step forms a highly doped P+ region (P+ front field) on the surface of the germanium wafer, which is used to optimize the front carrier collection efficiency and reduce contact resistance.
[0042] Step 3: Backside patterning etching (N-area location definition)
[0043] The operation is performed only on the back side of the germanium wafer. Patterning is achieved using laser etching or mask etching. The purpose of etching is to remove a portion of the P+ region on the back side, reserving precise locations for subsequent N-region deposition.
[0044] Step 4: Deposit phosphorus-doped nanocrystalline silicon thin film (N-region formation)
[0045] Only one side (back side) of the germanium wafer is subjected to PECVD (plasma-enhanced chemical vapor deposition) or PVD (physical vapor deposition). The deposited material is a phosphorus-doped nanocrystalline silicon thin film layer.
[0046] In some examples, the film thickness is controlled between 1 and 5 nm, and the doping concentration ranges from [missing value]. .
[0047] In some more specific examples, deposition using PECVD may include the following sub-steps: Evacuating the reaction chamber to a high vacuum, then heating the germanium substrate to a predetermined deposition temperature, for example, in the range of 150°C to 300°C. Introducing a process gas into the reaction chamber. The process gas comprises a silicon source gas, a hydrogen-diluted gas, and a phosphorus-doped source gas. Activating an RF power supply to generate plasma in the chamber, where the process gas decomposes and reacts to deposit a phosphorus-doped nanocrystalline silicon thin film layer on the back side of the germanium substrate. Continuing this deposition process until the film layer thickness reaches a predetermined value.
[0048] Step 5: Double-sided deposition of a-SiC x / Al2O3 / SiC stacked film (passivation layer)
[0049] Passivation films are deposited simultaneously on both sides of a germanium wafer. The deposition method can be any of PECVD, ALD (atomic layer deposition), PVD, etc. The deposited material is a-SiC. x / Al2O3 / SiC stacked film.
[0050] In some examples, multiple dielectric films are deposited sequentially, simultaneously forming passivation stacks on both sides of the germanium wafer. The deposition process is preferably performed continuously in different reaction chambers within the same vacuum system (e.g., a cluster tool) to avoid interface exposure to atmospheric contamination. In more specific examples, sequential deposition can be achieved using a double-sided PECVD system or a batch-type atomic layer deposition (ALD) furnace. And SiC.
[0051] Step 6: Selective local mold opening (contact hole formation) in the P and N areas on the back side.
[0052] The etching process involves creating a localized mold (contact hole etching) only on the back side of the germanium wafer. The molding method can be either laser etching or mask etching.
[0053] It should be noted that in some examples, the mold opening requirements for areas P and N differ:
[0054] P-area mold opening: The a-SiC surface must be opened. x / Al2O3 / SiC stacked film, and below it deposited phosphorus-doped nanocrystalline silicon thin film layer.
[0055] N-zone mold opening: Only the surface a-SiC needs to be opened. x / Al2O3 / SiC stacked film.
[0056] In some more specific examples, taking laser etching as an example, the process may include the following steps: Specifically, firstly, a first photoresist layer is deposited on the back side of the device. The first photoresist layer is patterned using a first mask to form a first opening at a predetermined location of the N-region contact hole. Next, a first etching is performed. Through the first opening, the a-SiC is selectively etched away. xThe etching of the Al2O3 / SiC stacked film terminates at the surface of the phosphorus-doped nanocrystalline silicon thin film layer, thereby exposing the N-region (i.e., the film formed in step 4). Subsequently, the first photoresist layer is stripped. Then, a second photoresist layer is deposited on the back side of the device. The second photoresist layer is patterned using a second mask to form a second opening at a predetermined location of the contact hole in the P-region. A second etching is then performed. Through the second opening, the passivation stacked film and the phosphorus-doped nanocrystalline silicon thin film layer are sequentially etched away, terminating at the surface of the P+ germanium substrate, thereby exposing the P-region. Subsequently, the second photoresist layer is stripped.
[0057] Step 7: Backside metal film deposition
[0058] A metal film is deposited on the back side of the device. The deposition method can be thermal evaporation or magnetron sputtering, etc., to deposit an aluminum film or aluminum-silicon film with a thickness of 1 to 10 micrometers.
[0059] Step 8: Patterning the back metal film (forming positive and negative electrodes)
[0060] The metal film deposited on the back side is patterned using a printing etching method. The purpose of patterning is to isolate the aluminum film in the P-region and N-region, thereby ultimately forming the positive and negative electrodes of the device.
[0061] According to the process steps of the above embodiments, the device obtained is as follows: Figure 2 As shown, it has at least the following beneficial effects:
[0062] 1. Increased front light-receiving area: Since all metal electrodes are located on the back of the device, there are no electrodes blocking the front of the device, which effectively increases the front light-receiving area and improves the front infrared radiation photoelectric conversion efficiency.
[0063] 2. Carrier collection optimization: By adding a P+ front field on the front side and a P+ layer in the P-region metal contact area on the back side, the collection efficiency of photogenerated carriers is effectively improved and the resistance of the contact area is reduced.
[0064] 3. Improved overall device performance: The above structural optimizations have improved the overall thermal radiation photoelectric conversion efficiency of the device.
[0065] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.
[0066] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the claimed invention.
Claims
1. A back contact thermal photovoltaic device manufacturing process, comprising the following steps: diffusing boron on a P-type substrate to form a P+ front field; etching the P+ front field on a part of the back surface of the substrate to reserve an area for forming an N region; depositing a phosphorus-doped nanocrystalline silicon thin film layer on the back surface of the substrate; depositing a stack film on the back surface or both surfaces of the substrate; partially opening the P region and the N region, wherein the opening of the P region includes opening the stack film and the phosphorus-doped nanocrystalline silicon thin film layer thereunder, and the opening of the N region includes opening the stack film; plating a metal film on the back surface to form a positive electrode and a negative electrode, and patterning the metal film on the positive electrode to isolate the metal film on the positive electrode from the metal film on the negative electrode.
2. The process for making a back contact thermal photovoltaic device of claim 1 wherein, The process conditions of the boron diffusion include diffusing boron at a temperature ranging from 900°C to 1050°C, and using boron trichloride as a gas source.
3. The process for making a back contact thermal photovoltaic device of claim 1 wherein, The thickness of the phosphorus-doped nanocrystalline silicon film layer is controlled to be 1 to 5 nm, and the doping concentration ranges from to .
4. The process for making a back contact thermal photovoltaic device of claim 1 wherein, The substrate is a P-type germanium wafer, and the metal film is an aluminum film or an aluminum-silicon film.
5. The back contact thermal photovoltaic device fabrication process of claim 1, wherein, The phosphorus-doped nanocrystalline silicon film layer is formed by PECVD or PVD deposition; the laminated film is formed by PECVD, ALD or PVD deposition; the laminated film is laminated film.
6. The back contact thermal photovoltaic device fabrication process of claim 1, wherein, The metal film is formed by evaporation or magnetron sputtering, the etching in the etching of the P+ front field on a part of the back surface of the substrate is laser etching or mask etching, and the patterning includes printing etching.
7. A back contact thermal photovoltaic device, comprising: a P-type substrate; a P+ front field formed on the front surface of the P-type substrate; a P region contact structure disposed on the back surface of the substrate, including a phosphorus-doped nanocrystalline silicon thin film layer formed on the back surface of the substrate, a stack film, and a metal electrode A penetrating through the stack film and the phosphorus-doped nanocrystalline silicon thin film layer and contacting the substrate; and an N region contact structure disposed on the back surface of the substrate, including a phosphorus-doped nanocrystalline silicon thin film layer formed on the back surface of the substrate, a stack film, and a metal electrode B penetrating through the stack film and contacting the phosphorus-doped nanocrystalline silicon thin film layer; wherein the metal electrode A is isolated from the metal electrode B.
8. The back contact thermal photovoltaic device of claim 7, wherein, The substrate is a P-type germanium wafer, and the metal electrode A and / or the metal electrode B is an aluminum film or an aluminum-silicon film.
9. The back contact thermal photovoltaic device of claim 7, wherein, A stack film is also deposited on the front side P+ front field of the substrate, the stack film being .
10. A photovoltaic device comprising the device prepared by the back contact thermal photovoltaic device manufacturing process according to any one of claims 1 to 6 or the back contact thermal photovoltaic device according to any one of claims 7 to 9.