KR100366350B1 - Solar cell and method for manufacturing the same - Google Patents

Abstract

First, irregular pyramid patterns are formed on the front and rear surfaces of a p-type silicon substrate, and n-type impurities such as phosphorus are diffused over the entire surface of the substrate to form an n + semiconductor layer. Subsequently, front and rear insulating films, which are antireflection films, are formed on the front and rear surfaces of the substrate through thermal oxidation. In this case, the front and rear insulating film is preferably formed to a thickness of about 2,500-3,500Å. Next, a front groove is deeply formed on the front surface of the substrate by using a laser or the like, and n-type impurities are heavily doped into the substrate exposed through the front groove to form an n ++ semiconductor layer. Next, a back groove is formed on the back of the substrate through laser or mechanical scribing. By forming the rear groove through the scribing can minimize the manufacturing cost. Next, an aluminum-based metal is deposited on the back of the substrate, and annealing is performed at a temperature range of about 300-500 ° C. to form a back electrode, and the front electrode 50 is formed in the front groove of the substrate on which the n ++ semiconductor layer is formed. To form.

Description

SOLAR CELL AND METHOD FOR MANUFACTURING THE SAME

The present invention relates to a solar cell and a method of manufacturing the same, and more particularly, to a solar cell and a method of manufacturing the same that can minimize the probability of recombination of the excited electrons in the rear surface facing the front surface where the emitter electrode is formed. .

A solar cell uses a band gap, which is a property of a semiconductor, as an electromotive force, and is formed by bonding an n-type and a p-type semiconductor. Here, electrons and holes are generated inside the semiconductor due to light energy incident on the junction of pn, and these electrons and holes are moved to the n-type and p-type semiconductor layers by the internal electric field, respectively, to the two electrodes on both sides. Accumulate. In this case, when the two electrodes are electrically connected to each other using a conductive current, a current flows in the conductive wire, and the external electrode can use this as electric power.

In such solar cells, it is important to maximize electron and hole generation, minimize loss of generated electrons and holes, and maximize output while minimizing voltage drop.

Solar cells may be classified into screen printing solar cells and buried contact solar cells according to the shape of the electrode. In a recessed contact solar cell, the front electrode is formed in a groove deeply formed into the front surface of the semiconductor substrate, which has a similar manufacturing cost but good energy change efficiency compared to the screen printed solar cell.

U.S. Patent Application No. 4,726,850 discloses a groove in the semiconductor layer of silicon to form a front electrode inside the groove, which greatly reduces the shading loss due to the front electrode and at the same time contacts the front electrode. The technique which can secure an area is described.

In addition, US Patent Application No. 4,589,191 describes a solar cell technology that can minimize the area of the electrode and apply a protective film made of silicon oxide on top of the semiconductor layer to reduce the recombination rate of electrons to improve energy conversion efficiency It is.

In this case, in order to form a back surface field on the rear surface facing the front electrode, aluminum is generally laminated and then sintered to form a back electrode. However, in the manufacturing method of such a structure, aluminum and silicon are alloyed in a long time high temperature heat treatment process during sintering, and thus, the silicon layer in the rear part is easily damaged, and the recombination of electrons and electrons is increased in this part, thereby reducing energy conversion efficiency. Occurs.

The technical problem to be achieved by the present invention is to minimize the recombination of electrons and holes generated from the back of the solar cell to solve this problem.

In addition, an object of the present invention is to minimize the manufacturing cost of the solar cell.

1 is a perspective view showing the structure of a solar cell in an embodiment of the present invention.

In order to achieve this problem, in the present invention, a rear insulating film is formed between the rear electrode and the semiconductor layer on the rear surface of the semiconductor substrate. In addition, a back groove is formed on the rear surface by using a laser when etching the rear insulating layer on the rear surface to contact the rear electrode and the semiconductor layer.

More specifically, pyramid patterns are formed on the front and rear surfaces of the p-type silicon substrate and n + semiconductor layers are formed on the front surface of the substrate. Next, an oxide film is formed on the front and rear surfaces of the substrate, and then a front groove is formed on the front surface of the substrate, and an n ++ semiconductor layer is formed on the substrate exposed through the front groove. Subsequently, a rear groove is formed on the rear surface, and a rear electrode is formed on the rear surface. Finally, a front electrode is formed on the n ++ semiconductor layer.

At this time, the step of forming the front groove and the rear groove is preferably formed through scribing, the rear electrode may be formed by laminating an aluminum-based metal on the back and annealing at a temperature range of 300-500 ℃. .

Here, the front electrode is preferably formed using either an electroless plating method or an electroplating method, and the oxide film is formed through thermal oxidation.

Then, with reference to the accompanying drawings will be described in detail with respect to the solar cell according to an embodiment of the present invention and its manufacturing method can be easily carried out by those of ordinary skill in the art.

1 is a perspective view showing the structure of a solar cell according to an embodiment of the present invention.

As shown in FIG. 1, an n-type impurity such as phosphorus (P) is formed on the top surface 11 of the p-type silicon substrate 10 having irregular pyramid patterns formed on the front surface 11 and the rear surface 12. The doped n + semiconductor layer 20 is formed thereon, and the front insulating film 30 made of silicon oxide is formed thereon. Here, the pyramid structure of the p-type substrate 10 improves light absorption compared to the flat structure. In addition, a front groove 40 is formed deep in the upper portion of the front surface of the p-type substrate 10, and a front electrode 50 is embedded in the front groove 40. By forming the front electrode 50 inside the front groove 40, the shading loss due to the front electrode 50 can be greatly reduced, and at the same time, the front electrode 50 is in contact with the substrate 10. The contact area can be secured. In this case, an n ++ semiconductor layer 60 is formed on the surface of the substrate 10 in contact with the front electrode 50 with a high concentration of n-type impurities, which is formed between the front electrode 50 and the silicon substrate 10. Serves to reduce contact resistance. The front electrode 50 collects the current generated in the silicon substrate 10 of the pn junction and contacts the external terminal, and is formed by plating a conductive metal by an electroless plating method or an electroplating method capable of selective plating. .

Meanwhile, a rear insulating film 70 made of silicon oxide is formed on the rear surface of the silicon substrate 10 having the same pyramid pattern as the front surface 11, and the rear surface 12 is the same as the front groove 40. Edo rear groove 90 is deeply formed. In addition, a rear electrode 80 made of aluminum is formed on the rear surface of the substrate 10 exposed through the rear insulating layer 70 and the rear groove 90 of the rear surface 12.

In the solar cell according to the embodiment of the present invention, the rear electrode 80 is connected to the substrate 10 only through the rear groove 90, and the rear surface is disposed between most of the remaining rear electrodes 80 and the plate 10. An insulating film 70 is formed. In this structure the rate of electron recombination at the backside 12 is significantly reduced while the reflected electrons move to the front face 11 and exit through the front electrode 50. Therefore, the conversion efficiency of energy can be maximized.

Next, a method of manufacturing a solar cell according to an embodiment of the present invention will be described in detail with reference to FIG. 1.

First, an irregular pyramid pattern is formed on the front surface 11 and the rear surface 12 of the p-type silicon substrate 10 by texturing. Here, by forming an irregular pyramid pattern using wet etching, production cost can be reduced and mass production is possible.

Next, n-type impurities such as phosphorous are diffused over the entire surface 11 of the substrate 10 to form the n + semiconductor layer 11. POCl ₃ or P ₂ O ₅ is used as the doping material for phosphorus.

Next, the front and back insulating films 30 and 70 made of silicon oxide are formed on the front surface 11 and the rear surface 12 of the substrate 10 through thermal oxidation. At this time, the front and rear insulating films 30 and 70 are preferably formed to a thickness of about 2,500-3,500 kPa.

Next, an n-type impurity is formed in the substrate 10 exposed through the front groove 40 by scribing the front groove 40 deeply using a laser or the like on the front surface 11 of the substrate 10. This high concentration is doped to form the n ++ semiconductor layer 60. Here, KOH solution is used to etch the melted silicon layer after laser scribing. The whole substrate is immersed in 30 weight% KOH and etched for 18-20 minutes. This process removes the silicon in the grooves 40 and reveals a clean silicon surface. Subsequently, in order to remove potassium ions remaining on the exposed silicon surface, the mixture is washed with HCl: H 2 O 2: H 2 O at 90 ° C. for 10-15 minutes. In the case of mechanical scribing, the same method is used to prevent damage to the silicon film.

Next, the rear groove 90 is formed on the rear surface 12 of the substrate 10 by laser or mechanical scribing in the same manner as the front groove 40. At this time, it is preferable that the width of the rear groove 90 is about 10-30 μm and the depth is about 10-20 μm. In this case, the insulating layer is removed from the rear groove 90 so that the substrate 10 is directly exposed. As such, by forming the rear groove 90 through scribing, manufacturing cost can be minimized.

Next, an aluminum-based metal is deposited to a thickness of about 1-2 μm through vacuum deposition on the rear surface 12 of the substrate 10, and annealing is performed at a temperature range of about 300 to 500 ° C. to form the rear electrode 80. Form.

Next, the front electrode 50 is formed in the front groove 40 of the substrate 10 on which the n ++ semiconductor layer 60 is formed. In this case, the front electrode 50 is selectively deposited on the front groove 40 of the substrate 10 by electroless plating or electroplating, and then sintered at 400 ° C. to form a silicide layer by reacting silicon with nickel. After forming, the nickel layer may be thinly deposited thereon, and the copper layer may be formed into a triple layer formed by depositing using an electroless plating method and an electroplating method.

As described above, according to the present invention, the rear electrode of the solar cell is connected to the substrate only through the rear groove, and most of them have an insulating film formed therebetween. Thus, the rate of electron recombination at the backside is significantly reduced, maximizing energy conversion efficiency. In addition, by forming the rear groove through the scribing like the front groove, it is possible to minimize the manufacturing cost.

Claims (6)

forming a pyramid pattern on a front surface of the p-type silicon substrate and a rear surface facing the front surface; Forming an n + semiconductor layer on the front surface of the substrate, Forming oxide films on the front and rear surfaces of the substrate, Forming a front groove in the front surface of the substrate; Forming an n ++ semiconductor layer on the substrate of the front groove; Forming a rear groove in the rear surface of the substrate, Forming a rear electrode on the rear surface of the substrate, Forming a front electrode on the n ++ semiconductor layer, Method for manufacturing a solar cell comprising a. In claim 1, The forming of the front groove and the back groove is formed by scribing a solar cell. In claim 1, The back electrode forming step, Stacking an aluminum-based metal on the rear surface of the substrate; Annealing in the 300-500 ° C. temperature range Method for manufacturing a solar cell comprising a. In claim 1, The front electrode is formed using any one of an electroless plating method or an electroplating method. In claim 1, The oxide film forming step is a method of manufacturing a solar cell formed through thermal oxidation. A p-type silicon substrate having an irregularly shaped pyramid pattern formed on a front surface and a rear surface opposite to the front surface, An n + semiconductor layer doped with n-type impurities on the front surface 11, A front insulating film formed on the n + semiconductor layer, A front groove formed on the front surface of the substrate, A front electrode embedded in the front groove, An n ++ semiconductor layer formed on the substrate in contact with the front electrode, A back insulating film formed on the back of the substrate, A rear groove deeply formed in the rear surface, A rear electrode formed on the rear surface exposed through the rear insulating film and the rear groove; Solar cell comprising a.