TWI408822B - Thin silicon solar cell and its manufacturing method - Google Patents

Abstract

The thin-film silicon solar cell of the present invention is provided with a silicon substrate. The substrate has a front surface and a back surface formed thereon an n-type doped layer and a p-type doped layer, respectively, wherein the n-type doped layer is of an amorphous silicon structure and an intrinsic amorphous silicon layer is arranged between the n-type doped layer and the substrate. The intrinsic amorphous silicon layer is formed by low-temperature plasma chemical vapor deposition or hot filament chemical vapor deposition method. The p-type doped layer is formed by using an intrinsic amorphous silicon layer combined with a metal layer and performing a low-temperature thermal diffusion thereon. Further, the n-type doped layer and p-type doped layer are formed over the surfaces of a first electrode layer and a second electrode layer.

Description

Thin twin crystal solar cell and manufacturing method thereof

The present invention relates to a thin twinned solar cell and a method of manufacturing the same, and aims to provide a thin twinned solar cell formed by a low temperature long film method and a low temperature thermal diffusion method, and a method of manufacturing the same.

In recent years, based on the high industrial development, the fossil energy on the earth has rapidly dried up, and environmental pollution has become increasingly serious. Therefore, all countries in the world are committed to the development of alternative energy sources based on energy demand and environmental reasons. Solar energy is the most abundant resource available to humans today, and it does not require transportation costs, cleanliness, and no increase in heat load on the Earth. Based on the above advantages, solar energy is one of the most renewable energy sources with the most potential for development today.

A solar cell is a semiconductor component that converts solar energy into electrical energy using a photovoltaic effect. Basically, any semiconductor diode converts light energy into electrical energy. The solar cell generates electrical energy based on two factors: photoconductive effect and internal electric field. Therefore, when selecting materials for solar cell power generation, it is necessary to consider the light guiding effect of the material and how to generate an internal electric field.

As we know, when light shines on a substance, one light will absorb the substance, and the other part will leave the substance by reflection or penetration. Based on this principle, one of the important considerations for selecting the material of a solar cell is the light absorption property of the light absorbing material, and the higher light absorbing property can increase the output power. The performance of solar cells is mainly judged by the conversion efficiency between photovoltaics. The factors affecting the conversion efficiency include sunlight intensity and temperature; material resistance and matrix quality, defect density; concentration and depth of pn junction; surface to light reflectance; metal electrode line width, line height, contact resistance Wait. Therefore, it is necessary to closely control various influence factors to produce a solar cell with high conversion efficiency.

Conversion efficiency and cost are the main considerations for the semiconductor materials currently selected for the manufacture of solar cells. At present, solar cells on the market, the market share of solar cells using bismuth as raw materials is large. According to the crystal structure classification, there are three kinds of single crystal solar cells, polycrystalline solar cells, and amorphous solar cells. In terms of theoretical conversion efficiency, the single crystal germanium solar cell is still higher, about 25%, the polycrystalline germanium is about 20%, and the amorphous germanium is about 15%. Using other compound semiconductors as photoelectric conversion substrates, such as III-V gallium arsenide (GaAs), the theoretical conversion efficiency can be as high as 26% or more.

The conversion efficiency and manufacturing cost of solar cells are significantly different according to their structure and process steps. High-efficiency solar cells are often complicated in structure and complicated in process steps, such as using multiple masks and multiple high-temperature processes, and using carrier life. The long-term but expensive FZ (floating zone)-grade germanium wafers have relatively high production costs and are disadvantageous in mass production. At present, most of the germanium wafers are manufactured by the Czochralski method, and then the resulting crystals are sliced into wafers to form a substrate for the solar cell.

Xi's production of silicon solar cell technology is generally made by double-sided low-temperature film formation method developed by Sanyo Co., Ltd., as shown in the fifth figure, which is mainly based on the front side of a crystal plate 31 at a low temperature film formation (for example Sputtering or plasma chemical vapor deposition) sequentially forms an intrinsic amorphous germanium layer 32 and an n-type amorphous germanium dopant layer 33, and sequentially forms an intrinsic amorphous germanium layer 32 and a p-type on the back side. The amorphous germanium dopant layer 36 is sequentially formed with a transparent conductive film 34 and electrode layers 35 and 37 on the surface of the n-type amorphous germanium dopant layer 33 and the p-type amorphous germanium dopant layer 36, respectively.

Since the cost is still the most important factor in the solar cell industry, today's solar cells typically have a thickness of 200 to 300 microns. If the thickness of the substrate is reduced, the cost can be reduced in mass production.

Although reducing the thickness of the ruthenium substrate can reduce the manufacturing cost, if the thickness is too thin, the bending deformation is likely to occur, and the degree of deformation increases with the size and the process temperature, and the degree of warpage is increased. However, the currently used high-temperature thermal diffusion fabrication of twin-crystal solar cell technology has not yet had an effective solution for thin-shaped germanium substrates (referring to thicknesses less than 150 μm). Therefore, it is imperative to overcome the deformation caused by the battery during the thinning of the substrate.

In order to solve the above problems, the present invention proposes a method of fabricating a thinned solar cell.

The main object of the present invention is to provide a thin twin crystal solar cell formed by a low temperature long film method and a low temperature thermal diffusion method, and a method of manufacturing the same.

In order to achieve the above object, the thin-type twin solar cell of the present invention is provided with a substrate, and an n-type dopant layer and a p-type dopant layer are respectively disposed on the front and back sides of the substrate, the n-type dopant layer and the p-type The surface of the dopant layer is provided with first and second electrode layers; wherein the n-type dopant layer is an amorphous germanium structure, which is formed by a low temperature long film technique such as plasma chemical vapor deposition or hot filament chemical vapor phase Formed by a deposition method. The p-type dopant layer on the other side is formed by vapor deposition of an amorphous germanium layer by a low temperature long film technique such as sputtering, and then formed by a low temperature thermal diffusion in combination with the metal layer.

The features of the present invention can be clearly understood by referring to the drawings and the detailed description of the embodiments.

According to the present invention, the basic structure of the thin twinned solar cell 10 of the present invention is as shown in the first figure, and comprises at least a substrate 11 which may be n-type or p- The intrinsic amorphous germanium layer 12 is disposed on a surface of the substrate 11. In the embodiment shown in the figure, the intrinsic amorphous germanium layer 12 is disposed on the front surface 111 of the substrate 11; The type of the doped layer 13 is disposed on the surface of the intrinsic amorphous layer 12; a transparent conductive film 14 is disposed between the n-type dopant layer 13 and the first electrode layer 15, and the transparent conductive film 14 may be a metal oxide transparent conductive film; the first electrode layer 15 is disposed on the surface of the transparent conductive film 14, as shown, the first electrode layer 15 may be a plurality of strip structures; a p-type dopant layer 16, On the other side surface of the substrate 11 with respect to the intrinsic amorphous germanium layer 12, in the embodiment shown in the figure, the p-type dopant layer 16 is disposed on the back surface 112 of the substrate 11, and the p-type dopant layer 16 is provided. It is formed by an intrinsic amorphous germanium layer combined with a metal layer formed by thermal diffusion crystallization under low temperature conditions; a transparent conductive film 14 is separately provided Between the p-type dopant layer 16 and the second electrode layer 17, the transparent conductive film 14 may be a metal oxide transparent conductive film; the second electrode layer 17 is disposed on the surface of the transparent conductive film 14, as shown in the figure The second electrode layer 17 may be a planar structure covered by the entire surface, or may be a plurality of strip structures as shown in the second figure; thus, a thin twinned solar cell 10 is constructed.

The method for manufacturing the thin-type twinned solar cell of the present invention is as shown in the third figure, and comprises at least the following steps: Step A, providing a substrate 11, as shown in the fourth figure (A), and on the substrate 11 The surface is cleaned; step B, a protective layer 21 is disposed on the front surface 111 of the substrate 11, and the protective layer 21 may be yttrium oxide. As shown in the fourth diagram (B), the yttrium oxide layer may be formed by a low temperature long film ( It can be formed by plasma chemical vapor deposition. The thickness of the yttrium oxide layer 21 is less than 50 nm; in step C, the other opposite surface (back surface 112) of the substrate 11 is formed by a low temperature film (which can be sputtered or A plasma amorphous vapor deposition layer 22 forms an intrinsic amorphous germanium layer 22, as shown in the fourth diagram (C), the thickness of the intrinsic amorphous germanium layer 22 is less than 30 nm; and step D, the amorphous germanium layer A metal layer 23 (which may be aluminum metal) is formed on the layer 22 by sputtering or thermal evaporation. As shown in the fourth diagram (D), the thickness of the metal layer 23 is less than 100 nm; step E, low temperature diffusion, The intrinsic amorphous germanium layer 22 and the metal layer 23 are crystallized to form a p-type dopant layer 16, as shown in the fourth diagram (E), when low temperature is performed In the case of dispersion, the p-type ytterbium dopant layer of different thickness, different crystallinity and conductivity can be achieved by the diffusion temperature, the diffusion time and the partial pressure of hydrogen in the diffusion atmosphere gas, as shown in Table 1 in Experiment 1 to Experiment. The four systems are conditions for different low-temperature diffusion, and have an effect on the crystallinity and electrical properties of the p-type tantalum dopant layer. The temperature of the low temperature diffusion of the present invention can be as low as 175 ° C, and is annealed in a hydrogen/argon mixed gas atmosphere of 10 to 38 Torr for 30 to 90 minutes, wherein the temperature in the second experiment is 200 ° C at 38 Torr. After hydrogen partial pressure annealing treatment for 30 minutes, after low temperature thermal diffusion, the formed conductivity is 4.1×10 ¹ (Ω×cm) ⁻¹ ;

Step F, after performing low-temperature diffusion in the step E, removing the metal layer, the yttrium aluminum alloy and the yttrium oxide protective layer remaining after the low-temperature diffusion by using a strong acid agent, wherein the back surface 112 of the substrate forms a p-type dopant layer 16 and the reactant layer 24, wherein the reactant layer 24 remaining after the low-temperature diffusion can be removed by a strong acid agent such as hydrochloric acid, as shown in the fourth diagram (F), leaving only the p-type dopant layer on the back surface of the substrate. After that, the yttrium oxide protective layer 21 on the front surface of the original substrate can be removed by hydrofluoric acid; in step G, the substrate is opposite to the surface of the p-type dopant layer 16 by a low temperature long film (which can be a plasma) A chemically vapor deposited or hot filament chemical vapor deposition method forms an intrinsic amorphous germanium layer 12 as shown in the fourth diagram (G); and a step H on the surface of the intrinsic amorphous germanium layer 12 by a low temperature long film ( An n-type dopant layer 13 may be formed for plasma chemical vapor deposition or hot filament chemical vapor deposition, as shown in the fourth diagram (H); step I, in the n-type dopant layer 13 and p The transparent dopant film 14 is respectively disposed on the surface of the type dopant layer 16, as shown in the fourth diagram (I); and the step J is respectively performed on the n-type dopant layer 13 The first and second electrode layers 15, 17 are formed on the transparent conductive film 14 on the surface of the p-type dopant layer 16, and the structure of the thin-type silicon solar cell 10 as shown in the fourth (J) and first drawings is formed.

It is worth mentioning that the present invention is a low-temperature long film (sputtering, plasma chemical vapor deposition or hot filament chemical vapor deposition) combined with low-temperature thermal diffusion to prepare the p-type doping required for the twin solar cell. The main layer structure is formed by the heterogeneous junction of the n-type dopant layer/twisted substrate on the other side, which not only has a simple molding method, but also avoids stress deformation of the thin substrate in a high-temperature process, wherein the low-temperature diffusion The conductivity of the p-type dopant layer can reach ~10 ^-1 (Ω×cm) ^-1 or more to improve the characteristics of the overall thin-type twin solar cell.

In summary, the present invention provides a preferred and feasible thin-type silicon solar cell and a manufacturing method thereof, and an application for an invention patent according to the law; the technical content and technical features of the present invention have been disclosed above, but are familiar with the present technology. It is still possible for a person to make various substitutions and modifications without departing from the spirit of the invention. Therefore, the scope of the present invention should be construed as being limited by the scope of the appended claims

10. . . Thin silicon solar cell

11. . . Substrate

111. . . positive

112. . . back

12. . . Intrinsic amorphous layer

13. . . N-type dopant layer

15. . . First electrode layer

14. . . Transparent conductive film

16. . . P-type dopant layer

17. . . Second electrode layer

twenty one. . . The protective layer

twenty two. . . Intrinsic amorphous layer

twenty three. . . Metal layer

twenty four. . . Reactive layer

31. . . Crystal plate

32. . . Intrinsic amorphous layer

33. . . N-type dopant layer

34. . . Transparent conductive film

35. . . Electrode layer

36. . . P-type dopant layer

37. . . Electrode layer

The first figure is a side view of the structure of the first embodiment of the thin-type twin solar cell of the present invention.

The second drawing is a side view of the structure of the second embodiment of the thin-type twin solar cell of the present invention.

The third figure is a schematic block diagram of a method for manufacturing a thin-type twin solar cell in the present invention.

The fourth (A) to (J) are structural schematic views of the manufacturing method of the thin-type twin solar cell of the present invention.

The fifth figure is a side view of the structure of a solar cell.

Claims (21)

A thin twin-crystal solar cell comprising at least: a substrate; an intrinsic amorphous germanium layer disposed on a surface of the substrate; an n-type dopant layer disposed on the surface of the intrinsic amorphous germanium layer, the n The type dopant layer may be formed of a phosphorus-doped amorphous germanium; a first electrode layer is disposed on the surface of the n-type dopant layer; and a p-type dopant layer is disposed on the substrate relative to the amorphous material a p-type dopant layer formed by another intrinsic amorphous germanium layer combined with a metal layer at a low temperature for thermal diffusion crystallization; and a second electrode layer disposed on the p-type doping layer The surface of the layer. The thin-type twinned solar cell of claim 1, wherein the metal layer is aluminum metal. The thin-type twin solar cell of claim 1, wherein the low-temperature heat diffusion temperature may be lower than 350 °C. The thin-type twinned solar cell according to claim 1, wherein the low temperature thermal diffusion temperature can be lower than 350 ° C, and annealed in a hydrogen/argon mixed gas atmosphere of 10 to 38 Torr hydrogen partial pressure 30 to 90 minute. The thin-type twinned solar cell of 3 or 4, wherein the low-temperature heat diffusion temperature may be 175 to 350 °C. The thin-type twinned solar cell of 3 or 4, wherein the substrate may be an n-type or p-type wafer substrate. The thin-type twinned solar cell of 3 or 4, wherein a transparent conductive film is disposed between the surface of the n-type dopant layer and the first electrode layer; and a transparent conductive film is disposed between the surface of the p-type dopant layer and the second electrode layer. Thin silicon solar cell according to 3 or 4, The n-type dopant layer is disposed on the front surface of the substrate, and the p-type dopant layer is disposed on the back surface of the substrate. A method for manufacturing a thin-type twinned solar cell, comprising at least the following steps: A, providing a substrate; C, providing an intrinsic amorphous germanium layer on a surface of the substrate; D, forming on the essential amorphous germanium layer a metal layer; E, performing low-temperature diffusion crystallization, the intrinsic amorphous germanium layer and the metal layer forming a p-type dopant layer; G, the substrate is formed on the other side surface of the p-type dopant layer An intrinsic amorphous germanium layer; H, forming an n-type dopant layer on the surface of the intrinsic amorphous germanium layer, the n-type dopant layer being formed by doped phosphorus-doped germanium; J, respectively, in the n-type doping A first electrode layer and a second electrode layer are formed on the surface of the layer and the surface of the p-type dopant layer. The method of manufacturing a thin-type silicon solar cell according to claim 9, wherein the step A and the step C further comprise a step B, wherein the step B is provided with a protective layer on the other opposite surface of the substrate. The method of manufacturing a thin-type twinned solar cell according to claim 10, wherein the protective layer may be ruthenium oxide. The method of manufacturing a thin-type twinned solar cell according to claim 9, wherein the metal layer is aluminum metal. The method for manufacturing a thin-type twinned solar cell according to claim 9, wherein the step E further comprises a step F of removing the metal layer remaining after the low-temperature diffusion, the bismuth aluminum alloy, and the strong acid agent. Cerium oxide protective layer. The method for producing a thin-type twinned solar cell according to claim 13, wherein the strong acid agent is hydrochloric acid or hydrofluoric acid. The method of manufacturing a thin-type twinned solar cell according to claim 12, wherein the thickness of the aluminum metal is less than 100 nm. The method for manufacturing a thin-type twinned solar cell according to claim 9, wherein when the step E is performed at a low temperature diffusion, the diffusion temperature, the diffusion time, and the partial pressure of hydrogen in the ambient gas can be controlled to achieve different thicknesses, different crystallinities, and electrical conductivity. P-type bismuth dopant layer. The method for manufacturing a thin-type twinned solar cell according to claim 9, wherein the step C is to form an intrinsic amorphous germanium layer by sputtering or plasma chemical vapor deposition; and the step G is by plasma chemistry. Vapor deposition or hot filament chemical vapor deposition forms an intrinsic amorphous germanium layer; in this step H, an n-type dopant layer is formed by plasma chemical vapor deposition or hot filament chemical vapor deposition. The method of manufacturing a thin-type twinned solar cell according to claim 9, wherein the temperature of the low-temperature heat diffusion may be lower than 350 °C. The method for manufacturing a thin-type twinned solar cell according to claim 9, wherein the low-temperature heat diffusion temperature can be as low as 175 ° C, and is annealed in a hydrogen/argon mixed gas atmosphere of 10 to 38 Torr hydrogen partial pressure. 30~90 minutes. The method of manufacturing a thin-type twinned solar cell according to claim 18, wherein the low-temperature heat diffusion temperature may be 175 to 350 °C. The method for manufacturing a thin-type twinned solar cell according to claim 9, wherein the step H and the step J further comprise a step I, the step I is disposed on the surface of the n-type dopant layer and the p-type dopant layer. Transparent conductive film.