Thermophotovoltaic device preparation process and thermophotovoltaic device

Abstract

The invention discloses a preparation process of a thermophotovoltaic device and the thermophotovoltaic device. The preparation process comprises the following steps: carrying out double-sided polishing treatment on a germanium wafer; depositing a phosphorus-doped nanocrystalline silicon thin film layer on the back surface of the germanium wafer; printing photoresist on the nanocrystalline silicon thin film layer, and forming spaced P pole regions in a manner of exposure, development and etching reduction; a-SiCx / AI2O3 / SiC laminated film deposition is respectively carried out on the front surface and the back surface of the germanium sheet; plating a layer of aluminum film on the back surface of the germanium sheet; doping the aluminum element part laser in the aluminum film into the germanium sheet substrate to form contact in the P pole region by adopting infrared laser; and separating the aluminum films of the P-pole region and the N-pole region by adopting a printing etching mode to form a positive electrode and a negative electrode. According to the manufacturing process and the photovoltaic device provided by the invention, the front single side is not provided with an electrode and is not shielded, the front light receiving is increased, and the front infrared radiation photoelectric conversion efficiency is improved; the preparation process is simple, and the metallization of the electrode does not need high temperature and is low in cost.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of thermal photovoltaic power generation in solar photovoltaic power generation, and mainly aims at how to effectively convert long-wave infrared radiation into electric energy. BACKGROUND

[0002] Thermal photovoltaic (TPV) technology converts radiant heat into electricity through thermal emission photons incident on photovoltaic cells. Given that TPV systems can use a variety of heat sources to fuel the TPV system, TPV technology has many potential applications, such as: cogeneration in residential applications, power generation in spacecraft, power from thermal energy storage systems or waste heat recovery in heavy industrial processes, waste heat recovery in photovoltaic systems to reduce photovoltaic component temperature to improve photovoltaic component power generation efficiency and reduce the risk of high temperature. One of the main challenges of TPV is to develop a cost-effective manufacturing process for high-efficiency cells. 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 involves the use of crystalline germanium (Egap = 0.67 eV) as a photon absorber. Although germanium is an indirect bandgap semiconductor, it has a lower absorption coefficient than other low-bandgap materials such as InGaAs, but the benefits of germanium for TPV systems come mainly from a cost perspective. On the one hand, germanium-silicon wafers are cheaper than InP. On the other hand, the expensive epitaxial technology can be avoided, as germanium, as a group IV material, is highly compatible with silicon technology, allowing the implementation of thin film deposition techniques such as PECVD and ALD, which are standard methods in the silicon solar cell industry.

[0003] Therefore, despite the inherent limitations, germanium-based technology is a snapshot of a cost-effective strategy to develop TPV cells, with viable prospects for industrial scalability. SUMMARY

[0004] In view of the deficiencies of the prior art, the present application aims to provide a new TPV device preparation process based on amorphous silicon carbide (a-SiCx) and aluminum oxide (Al2O3) thin film passivation without electrode blocking on the thermal radiation receiving surface.

[0005] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is as follows: In one aspect, the present application provides a thermal photovoltaic device preparation process, which comprises the following processes: Polishing both sides of a germanium wafer; Depositing a phosphorus-doped nanocrystalline silicon thin film layer on the back surface of the germanium wafer; Printing photoresist on the nanocrystalline silicon thin film layer, and forming spaced P-polar regions by exposure, development, and additive or subtractive etching; The front surface and back surface of the germanium sheet are respectively deposited with a-SiCx / Al2O3 / SiC laminated film; An aluminum film is plated on the back surface of the germanium sheet; The aluminum element in the aluminum film is partially laser-doped into the germanium sheet substrate to form a contact in the P-pole region by using an infrared laser; The aluminum films of the P-pole region and the N-pole region are separated by printing and etching to form the positive and negative poles.

[0006] Further, the nanocrystalline silicon thin film layer is deposited by PECVD or PVD.

[0007] Further, the width of the spaced P-pole region is 300-500um, and the spacing is 500-1000um.

[0008] Further, the thickness of the aluminum film is 1-10 microns.

[0009] In another aspect, the application also provides a thermal photovoltaic device, which is prepared according to the above preparation process.

[0010] The beneficial effects of the application are: 1. The front surface is single-sided without electrode and shielding, which increases the front light receiving and improves the front infrared radiation photoelectric conversion efficiency; 2. The process preparation flow is simple, and the electrode metallization does not require high temperature and has low cost; 3. The back surface of the whole metal film (positive and negative poles are separated) is conducive to reflecting the long-wave infrared radiation light incident through the cell, further increasing the infrared radiation photoelectric conversion efficiency. BRIEF DESCRIPTION OF DRAWINGS

[0011] In order to more clearly illustrate the technical solutions of the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiment or prior art description. Obviously, the drawings in the following description are only some embodiments of the application, and for those skilled in the art, other drawings can also be obtained without creative labor.

[0012] Figure 1 The thermal photovoltaic device structure for infrared radiation light prepared by the method of the application is shown in the figure; Figure 2 The flowchart of the method of the application is shown in the figure. DETAILED DESCRIPTION

[0013] In order to facilitate the understanding of those skilled in the art, the application will be further described below in conjunction with the embodiments and the drawings. The content mentioned in the embodiments is not a limitation of the application.

[0014] Example 1:

[0015] As Figure 2 shown, the preparation process of a thermal photovoltaic device of the present application, the metal electrode is on the back of the device, the thermal photovoltaic device structure and preparation process, increase the light receiving area of the front; through the special process preparation process, low-cost implementation of this structure battery preparation process flow: 1. P-type germanium wafer with resistivity of 0.1-5 Ω.cm, double-side polishing treatment.

[0016] 2. Single-sided (back) deposition of phosphorus-doped nanocrystalline silicon film layer by PECVD or PVD, thickness 1-5 nm, doping concentration 1E16-1E20 cm-3.

[0017] 3. Backside patterning: front side printing photoresist, through exposure and development, subtractive etching to form spaced P-poles, width 300-500 um, spacing 500-1000 um.

[0018] 4. Double-sided a-SiCx / Al2O3 / SiC deposition.

[0019] 5. Backside deposition of 1-10 micron thick aluminum film by thermal evaporation, magnetron sputtering, etc.

[0020] 6. Using infrared laser (wavelength 1064 nm) in P-pole, part of aluminum element in aluminum film is laser-doped into germanium substrate to form contact.

[0021] 7. Backside patterning by printing and etching to separate P / N area aluminum film to form positive and negative electrodes.

[0022] One of the main challenges for TPV cells is to develop cost-effective manufacturing processes for high-efficiency cells. Record-breaking efficiencies can be achieved using low-bandgap III-V semiconductor compounds, most of which are grown epitaxially on InP substrates. A viable alternative to this approach includes the use of crystalline germanium (Egap = 0.67 eV) as a photon absorber. Although germanium is an indirect bandgap semiconductor, with a lower absorption coefficient than other low-bandgap materials such as InGaAs, the benefits of germanium for TPV systems come mainly from the cost angle. On the one hand, germanium silicon wafers are cheaper than InP. On the other hand, the expensive epitaxial technology can be avoided, as germanium, being a group IV material, is highly compatible with silicon technology, allowing the implementation of thin film deposition techniques such as PECVD and ALD, which are standard methods in the silicon solar cell industry.

[0023] Example 2:

[0024] As Figure 1 shown, the present application also provides a thermal photovoltaic device, which is prepared according to the above preparation process.

[0025] The preparation process of the thermophotovoltaic device provided in the present application is based on a germanium-based scheme, and the main cost advantages are: 1. The cost of the substrate is significantly reduced: Germanium wafer (Ge): relatively cheap. Although more expensive than silicon wafers, it is much lower than III-V substrates. The mature germanium wafer production process (mainly from the infrared optical and optical fiber industries) has the advantage of economies of scale. The diameter is usually up to 200 mm (8 inches).

[0026] Compared with InP wafer, InP wafer is very expensive. It is difficult to produce, has a low yield, and the diameter is usually small (commonly 100 mm / 4 inches or 150 mm / 6 inches). Its cost is one of the main burdens in the cost structure of germanium-based cells.

[0027] 2. The manufacturing process cost is greatly reduced: Avoiding expensive epitaxy: this is the most critical advantage. InP-based high-efficiency cells (such as InGaAs) must use ultra-clean, high-vacuum, and high-precision epitaxy technologies such as MBE or MOCVD. These devices are extremely expensive (several million dollars each), have high operating costs (high-purity gases, high energy consumption), slow growth rates, complex processes, and high yield management challenges.

[0028] The present application uses silicon-compatible deposition technology (PECVD, ALD), PECVD (plasma-enhanced chemical vapor deposition): widely used in the silicon-based photovoltaic and semiconductor industries. The cost of the equipment is much lower than that of MOCVD / MBE, the operating cost is low, the deposition rate is fast, and it is suitable for large-area production. ALD (atomic layer deposition): mainly used for high-quality passivation layers or ultra-thin layers. The equipment is relatively mature (especially in advanced semiconductor manufacturing), and its application in silicon-based devices is increasing, and the cost-effectiveness is better than epitaxy.

[0029] 3. Great potential for economies of scale: The silicon solar cell and semiconductor industry has a large and highly optimized manufacturing infrastructure and supply chain. If the germanium-based TPV cell can fully utilize these facilities and standardized processes, its large-scale production cost can be reduced to a very low level.

[0030] III-V epitaxial production lines are usually dedicated, small-scale, and high-cost.

[0031] Estimation of the cost reduction of the thermophotovoltaic device prepared by the process provided in the present application: It is generally believed that low-bandgap cells (such as germanium-based) manufactured using silicon-compatible technology can reduce the manufacturing cost by an order of magnitude (i.e., by a factor of 10) or more compared to III-V cells (such as InGaAs / InP) grown by epitaxy, while achieving the same efficiency. The specific value may be in the range of 70% to 90% reduction.

[0032] This approach avoids the extra cost of epitaxial production lines: this is likely to be the single largest source of cost reduction, potentially contributing more than 50% of the total cost reduction. Epitaxial equipment depreciation, consumables (special gases, source materials), high energy consumption and high-skilled operator costs are the main factors. Once in mass production, the cost advantages of leveraging the silicon industry ecosystem scale exponentially.

[0033] The application has many specific application approaches, and the above description is only the preferred embodiment of the application. It should be pointed out that for ordinary skilled persons in the technical field, some improvements can be made without departing from the principles of the application, and these improvements should also be considered as the protection scope of the application.

Claims

1. A process for fabricating a thermophotovoltaic device, characterized in that, The preparation process includes the following steps: The germanium sheet is polished on both sides. A phosphorus-doped nanocrystalline silicon thin film layer is deposited on the back side of the germanium wafer; Photoresist is printed on the nanocrystalline silicon thin film layer, and spaced P-polar regions are formed by exposure, development, and etching. The front and back sides of the germanium sheet are respectively deposited with a-SiCx / Al2O3 / SiC stacked films; An aluminum film is deposited on the back of the germanium sheet; Infrared lasers are used in the P-polar region to laser-dopick the aluminum element in the aluminum film into the germanium substrate to form a contact; The aluminum films of the P-region and N-region are separated by printing and etching to form the positive and negative electrodes.

2. The fabrication process of a thermophotovoltaic device according to claim 1, characterized in that, The nanocrystalline silicon thin film layer is deposited by PECVD or PVD.

3. The fabrication process of a thermophotovoltaic device according to claim 1, characterized in that, The width of the P-polar region of the interval is 300-500 μm, and the interval is 500-1000 μm.

4. The fabrication process of a thermophotovoltaic device according to claim 1, characterized in that, The thickness of the aluminum film is 1-10 micrometers.

5. A thermophotovoltaic device, characterized in that, The device is prepared using the fabrication process described in claim 1.

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