KR100446597B1 - Method of manufacturing recessed electrode type solar cell - Google Patents

Abstract

The present invention provides a method of manufacturing a recessed electrode type solar cell. The method comprises the steps of texturing a p-type silicon substrate and then cleaning; Spin-coating phosphorus (P) -containing silicon glass on the entire surface of the substrate and then baking; Forming a groove into the entire surface of the silicon substrate and then etching the groove; Electroless plating the phosphorus compound-containing nickel (Ni) plating solution into the grooves; Depositing aluminum on the backside of the silicon substrate; Forming gas annealing step; And plating copper over the nickel-plated grooves. According to the present invention, the manufacturing process is simplified by enabling the formation of emitters, diffusion in grooves and heat treatment of metals in a single high temperature process.

Description

Method of manufacturing recessed electrode type solar cell

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a recessed electrode type solar cell, wherein a method for manufacturing a recessed electrode type solar cell is simplified by enabling the formation of an emitter, diffusion in a groove, and heat treatment of a metal in a single high temperature process. It is about.

A general manufacturing process of a recessed electrode type solar cell includes a high temperature process, that is, forming an emitter, forming an oxide film, diffusing into a groove, sintering aluminum on the back of the substrate, and metal sintering at the time of forming the substrate front electrode. Furnace is required. During the high temperature process, since contaminants are easily introduced into the semiconductor substrate, it is necessary not only to continuously supply an inert gas to prevent contamination, but also increase the importance of the cleaning process.

Due to the factors described above, the solar cell manufactured according to the prior art is in a difficult state of practical use because of high manufacturing cost.

As one of efforts to reduce the manufacturing cost of solar cells, a method of replacing a single crystal silicon substrate with a polycrystalline silicon substrate or an amorphous silicon substrate has been attempted as a semiconductor substrate. However, this method did not yield satisfactory results. In other words, if a polycrystalline silicon substrate is used instead of a single crystal silicon substrate, the cost of the substrate can be lowered, but there is a lack of reproductivity for water, and an amorphous silicon substrate is undesirable in terms of degradation and efficiency. I couldn't.

In order to solve the above problems, the present invention provides a method of manufacturing a recessed electrode type solar cell, in which an emitter is formed, diffusion in a groove, and heat treatment of a metal are performed in a single high temperature process. To provide.

In order to achieve the above object, the present invention comprises the steps of: (a) texturing the p-type silicon substrate, and then cleaning; (b) spin-coating phosphorus-containing silicon glass on the entire surface of the substrate and then baking; (c) forming a groove into the entire surface of the silicon substrate and then etching the groove; (d) electroless plating a phosphorus compound-containing nickel (Ni) plating solution on the grooves; (e) depositing aluminum on the backside of the silicon substrate; (f) forming gas annealing step; And (g) plating copper over the nickel-plated grooves.

In addition, an object of the present invention is to (a) texturing the p-type silicon substrate, then cleaning; (b) spin-coating phosphorus (P) -containing silicon glass on the entire surface of the substrate and then baking; (c) spin-coating boron (B) -containing silicon glass on the back side of the substrate and then baking; (d) forming a groove in the entire surface of the silicon substrate and then etching the groove; (e) electroless plating a phosphorus compound-containing nickel (Ni) plating solution on the grooves; (f) forming a groove into the back side of the silicon substrate and then etching the groove; (g) spin-coating an oxide in the groove in front of the silicon substrate, and then baking to form an oxide film; (h) electroless plating a boron compound-containing nickel (Ni) plating solution into the groove on the rear surface of the silicon substrate; (i) weakening and then removing the oxide film formed in the groove in front of the silicon substrate; (j) forming gas annealing step; And (k) is also made by the method of manufacturing a recessed electrode type solar cell, characterized in that it comprises the step of plating a copper on the upper grooves of the front and rear of the silicon substrate.

In a typical recessed electrode type solar cell, in order to completely separate the metal electrode from the active region of the cell, it is common to deeply dope n-type or p-type impurities in the groove region where the electrode is formed. In the present invention, the doping step of the impurity and the metal plating layer forming process are performed at the same time.

Hereinafter, the principle of the electroless plating process using a nickel (Ni) plating solution containing a phosphorus (P) compound will be briefly described.

Nickel plating is performed by catalytic reduction of nickel ions in the presence of hypo-phosphite ions. In an aqueous medium, the hypo-phosphite anion is oxidized to phosphite ions while generating H, and the reaction rate depends on the concentration and temperature of the hypo-phosphite ions (Scheme 1).

The oxidation reaction occurs simultaneously in the same phase reaction under high temperature and alkaline solution, whereas in neutral or moderate acidic conditions, the oxidation proceeds in the presence of Group VIII metal element, for example, Pd, Ni, etc. (catalytic in-phase reaction).

As mentioned above, the electroless plating reaction is a catalytic dehydrogenation reaction of hypo-phosphite molecules.

If metal cations such as nickel are present under neutral or suitable acidic conditions, plating continues on the catalytic metal surface until the hypo-phosphite ions or the nickel cations are lost. The overall reaction at this time is as follows.

The reduction of nickel ions is achieved by the absorption of atoms H on the metal surface. Simultaneously with this reaction, a second reaction between hypo-phosphite ions, atoms H and nickel cations occurs to form nickel phosphide Ni ₃ P (which may form a phosphite salt as an intermediate compound).

If this is expressed as a basic scheme, it is the same as Schemes 3, 4, 5, 6 and 7.

As can be seen from Scheme 3-7, as the reaction proceeds, a Ni ₃ P alloy is formed, which itself serves as a catalyst. Therefore, as time passes, the coating thickness is continuously increased for a certain time, and gradually limited as the pH of the plating solution and the ion concentration of the reactants decrease.

The principle of electroless plating using boron-containing nickel plating liquid is the same as that of electroless plating using phosphorus-containing nickel plating liquid except that NiB is produced instead of Ni ₃ P.

Hereinafter, a method of manufacturing single sided and double sided double-sided depressed electrode solar cells according to the present invention will be described with reference to the accompanying drawings.

1A-F illustrate a manufacturing procedure of the cross-sectional recessed electrode solar cell.

Referring to this, first, the p-type silicon substrate 11 is textured, and then the substrate is cleanly cleaned. Phosphorus-containing silicon glass is spin-coated on the entire surface of the cleaned substrate 11 and then baked to sequentially form the n ⁺ -type semiconductor layer 12 and the oxide film 13 (FIG. 1A). The concentration of phosphorus in the phosphorus-containing silicon glass here is preferably 5 to 10%, in particular about 10%. And the baking conditions are carried out for 15 to 20 minutes at 150 to 200 ℃, particularly preferably for about 20 minutes at about 200 ℃.

Subsequently, a groove 14 is formed on the entire surface of the silicon substrate 11, and then the inside of the groove is etched (FIG. 1B). The groove etch here is effected by carrying out 15-20 minutes, in particular about 20 minutes, using a KOH solution at 50-55 ° C.

The etched groove 14 is plated using a phosphorus compound-containing nickel plating solution (FIG. 1C). As the nickel plating solution, any conventional nickel plating solution may be used, and specific examples thereof include a nickel plating solution containing NaH ₂ PO ₂ and NiCl ₂ . Here, the conditions at the time of plating using the said nickel plating liquid are 5 to 15 minutes at 90-97 degreeC.

Aluminum is deposited on the back surface of the silicon substrate to form an aluminum layer 15 (FIG. 1D). At this time, the thickness of the aluminum layer is preferably 1 to 2㎛.

Next, forming gas annealing is performed. At this time, the experimental conditions are carried out for 20 to 60 minutes at 800 to 900 ℃. In this annealing process, the groove 14 on the front of the silicon substrate has an n ⁺ type The semiconductor layer 12 'and the nickel plating layer 16 are sequentially stacked (FIG. 1E).

Thereafter, copper is plated on the nickel plating layer 16 on the entire surface of the silicon substrate to form a copper (Cu) plating layer 17 (FIG. 1F).

2a-j is a view showing a manufacturing process sequence of a double-sided recessed electrode solar cell.

Referring to this, first, the p-type silicon substrate 21 is textured and then the substrate is cleaned cleanly. Phosphorous (P) -containing silicon glass is spin-coated on the entire surface of the cleaned substrate 21, followed by baking to sequentially form the n ⁺ -type semiconductor layer 22 and the oxide film 23 (FIG. 2A). Here, the concentration of phosphorus in the silicon glass or baking conditions are the same as in the case of manufacturing a single-sided recessed electrode solar cell.

Subsequently, after spin-coating a boron (B) -containing silicon glass on the rear surface of the substrate 21, the p ⁺ type The semiconductor layer 24 is formed (FIG. 2B). Here, the content of boron in the silicone glass is 5 to 10%, particularly preferably about 10%.

Thereafter, grooves 25 are formed on the entire surface of the silicon substrate, and the grooves are etched (FIG. 2C). Here, the groove etching conditions are the same as in the case of manufacturing the cross-sectional recessed electrode solar cell.

The plating is performed using a nickel plating solution containing a phosphorus compound, for example, NaH ₂ PO ₂ and NiCl ₂ , on the etched groove 25 (FIG. 2D). Thereafter, a groove 25 'is formed in the rear surface of the silicon substrate 21, and then the inside of the groove 25' is etched (FIG. 2E).

When etching of the grooves 25 'on the rear surface of the silicon substrate 21 is completed, an oxide film 23' is formed on the grooves 25 on the silicon substrate front surface (FIG. 2F). After masking the front grooves 25 of the substrate 21 in this manner, the boron compound-containing nickel plating solution is electroless plated on the grooves 25 'on the rear surface of the silicon substrate (FIG. 2G). As the boron compound-containing nickel plating solution, any conventional nickel plating solution can be used. Specific examples thereof include a nickel plating solution containing NaBH ₄ and NiCl ₂ .

Thereafter, the oxide film 23 'formed in the groove 25 on the entire surface of the silicon substrate is weakened and then removed (FIG. 2H).

Next, forming gas annealing is performed (FIG. 2I). In this annealing process, the groove 25 on the front of the silicon substrate 21 has an n ⁺ type The semiconductor layer 22 'and the nickel plating layer 26 are sequentially stacked, and a p ⁺ type is formed in the groove 25' behind the silicon substrate 21. The semiconductor layer 24 'and the nickel plating layer 26' are sequentially stacked.

Thereafter, copper is plated on the nickel plating layers 26 and 26 'on the front and rear surfaces of the silicon substrate to form copper plating layers 27 and 27', respectively (FIG. 2J).

As described above, in the manufacturing method of the present invention, the emitter formation, the nickel plating layer formation, and the sintering of the plating layer are performed by only one step. According to such a manufacturing process, it has an efficiency of 16 to 18% for the single-sided depressed electrode solar cell and about 19% for the double-sided depressed electrode solar cell.

According to the present invention, it has the following effects.

First, up to two furnaces may be used for emitter formation, oxide film formation and electrode formation. And if a spin-on source is used for emitter formation and oxide weakening, there may be only one furnace equipment. When the number of furnaces can be reduced in this way, the cost of nitrogen or oxygen gas supplied to the furnace is reduced, resulting in a lower battery manufacturing cost.

Second, it is not necessary to use an expensive high quality substrate as a substrate. That is, various kinds of substrates including a polycrystalline substrate can be used.

Third, since the number of high-temperature processes is reduced, the contamination rate is low, so the necessity and importance of the cleaning process is less than that of conventional solar cells. Therefore, the cost of the conventional washing process can be reduced.

Due to the effects as described above, the depressed electrode solar cell manufactured according to the present invention can stand in an advantageous position that can advantageously compete with conventional fossil fuels.

1a-f is a view sequentially showing a manufacturing process of the cross-sectional recessed electrode solar cell according to the present invention,

Figure 2a-j is a view sequentially showing the manufacturing process of the double-sided depressed electrode solar cell according to the present invention.

<Explanation of symbols for the main parts of the drawings>

11, 21 ... p-type silicon substrate 12, 12 ', 22, 22' .. n ⁺ type semiconductor layer

13, 23, 23 '... oxide 14, 25, 25' ... home

15 ... aluminum layer 24, 24 '... p ⁺ type semiconductor layer

16, 26, 26 'Nickel plated layer

17, 27,27 '... Copper plated layer

Claims (12)

(a) texturing the p-type silicon substrate and then cleaning; (b) spin-coating phosphorus-containing silicon glass on the entire surface of the substrate and then baking; (c) forming a groove into the entire surface of the silicon substrate and then etching the groove; (d) electroless plating a phosphorus compound-containing nickel (Ni) plating solution on the grooves; (e) depositing aluminum on the backside of the silicon substrate; (f) forming gas annealing step; And (g) a method of manufacturing a recessed electrode type solar cell, comprising the step of plating copper on the nickel-plated groove. The method of claim 1, wherein the concentration of phosphorus in the step (b) is 5 to 10%, baking is performed for 15 to 20 minutes at 150 to 200 ℃ method of manufacturing a recessed electrode type solar cell. The method of claim 1, wherein in the step (c), the etching step is performed at 50 to 55 ° C. for 15 to 20 minutes using an alkaline solution. The method of claim 1, wherein the step (d) is carried out at 90 to 97 ℃ for 5 minutes to 15 minutes. The method of claim 1, wherein the step (f) is performed at 800 to 900 ° C. for 20 to 60 minutes. (a) texturing the p-type silicon substrate and then cleaning; (b) spin-coating phosphorus (P) -containing silicon glass on the entire surface of the substrate and then baking; (c) spin-coating boron (B) -containing silicon glass on the back side of the substrate and then baking; (d) forming a groove in the entire surface of the silicon substrate and then etching the groove; (e) electroless plating a phosphorus compound-containing nickel (Ni) plating solution on the grooves; (f) forming a groove into the back side of the silicon substrate and then etching the groove; (g) spin-coating an oxide in the groove in front of the silicon substrate, and then baking to form an oxide film; (h) electroless plating a boron compound-containing nickel (Ni) plating solution into the groove on the rear surface of the silicon substrate; (i) weakening and then removing the oxide film formed in the groove in front of the silicon substrate; (j) forming gas annealing step; And (k) a method of manufacturing a recessed electrode type solar cell, comprising the step of plating copper on upper portions of the grooves on the front and rear surfaces of the silicon substrate. The method of claim 6, wherein the concentration of phosphorus in the step (b) is 5 to 10%, baking is carried out for 15 to 20 minutes at 150 to 200 ℃ method of manufacturing a recessed electrode type solar cell. The method of claim 6, wherein the concentration of boron in the step (c) is 5 to 10%, baking is performed for 15 to 20 minutes at 150 to 200 ℃ method of manufacturing a recessed electrode type solar cell. The method of claim 6, wherein the etching step in the steps (d) and (f) is performed for 15 to 20 minutes at 50 to 55 ℃ using an alkaline solution. The method of claim 6, wherein in the step (e), the electroless plating is performed at 90 to 97 DEG C for 5 to 15 minutes. The method of claim 6, wherein in the step (g), the baking is performed at 150 to 200 ° C. for 15 to 20 minutes. The method of claim 6, wherein the step (j) is performed at 800 to 900 ° C. for 20 to 60 minutes.

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