CN101226968A - Method for reducing series resistance of concentrating solar cell and concentrating solar cell obtained by the method - Google Patents

Abstract

The invention provides a method for reducing the series resistance of a concentrated solar cell with a doped semiconductor material body, the concentrated solar cell manufactured by the method has a doped semiconductor material body, through the following steps: Make weldable electrode conductor elements on the incident surface, and weldable electrode conductor elements on the back, whose position is just staggered from the electrode conductor elements on the light incident surface; make aluminum layers on other positions on the back as the back field; make anti-reflection films on the light reflection surface; Metallization and sintering of the electrode conductor elements; scribing along the light incident surface of the semiconductor material and staggered positions of the electrode conductor elements on the back; finally forming a concentrated solar cell with low series resistance.

Description

Method for reducing series resistance of concentrating solar cell and concentrating solar cell obtained by the method

technical field

The invention relates to a method for reducing the series resistance of a concentrating solar cell with a doped semiconductor material body; in addition, the invention also relates to a concentrating solar cell manufactured by using the method, which belongs to the field of solar photovoltaic power generation.

Background technique

At present, because the production technology of high-purity monocrystalline and polycrystalline silicon is monopolized by several foreign high-tech enterprises, the price of crystalline silicon remains high, and solar photovoltaic power generation systems require a large amount of monocrystalline and polycrystalline silicon, which directly leads to the high cost of solar power generation. The cost of photovoltaic power generation is about 4-5 yuan/KwH, which is about 10 times the cost of thermal power, so the large-scale promotion and application of solar power generation projects is hindered.

At the same time, experts at home and abroad have found that the use of crystalline silicon photovoltaic cells under normal sunlight intensity is actually overkill, because crystalline silicon photovoltaic cells can withstand higher light intensity, and the emitted current increases proportionally without Affect the life of photovoltaic cells. If the light intensity of the photovoltaic cell area is increased by dozens or even hundreds of times of concentrated light, the area of the photovoltaic cell that outputs the same power current can be greatly reduced. In this way, the crystalline silicon of the solar panel The amount of usage can be greatly reduced, and the cost of solar photovoltaic power generation can be greatly reduced, approaching the cost of wind power generation or hydropower, and reaching a level that users can accept.

However, people have found through experiments that under the condition of sufficient heat dissipation, ordinary solar cells can obtain 4.8 times the power output with 6 times the intensity of concentrated sunlight, but if the light intensity continues to increase, it is found that the actual power output does not There is no continuing to scale linearly.

Therefore, researching concentrating solar cells with high-magnification concentrating power and synchronously increasing power output has become a difficult task for photovoltaic scientists. Better semiconductor material gallium arsenide and so on. However, due to various reasons, these technologies have basically not formed mass production, that is to say, they have no good economic value.

Through a large number of experimental analysis, the research concluded that the main factor affecting the power output of concentrating solar cells is the series resistance, that is, the volume resistance of the semiconductor, the surface square resistance, and the electrode conductor resistance and the contact resistance between the electrode and the silicon surface. The higher the series resistance, the faster the conversion efficiency of the concentrating cell will drop as the light intensity increases.

The bulk resistance of a semiconductor depends on the material selection of the semiconductor, and cannot be improved by improving the processing technology; the lower the surface sheet resistance, the better, the lower the surface sheet resistance, the recombination speed of electrons and holes will also be exponentially proportional It is not conducive to a large number of photogenerated electron-hole pairs, so this value also has a certain value range, such as: 20Ω/□-100Ω/□, conventional concentrated solar cell products can be made lower, but not It can be made too low, and the proportion of these two resistors is relatively small relative to the composition of the entire series resistor.

If it is necessary to effectively reduce the resistance value of the series resistance, only the "electrode conductor resistance" and "contact resistance between the electrode and the silicon surface" can be improved, such as: ①, use better electrode conductive materials; ②, widen the electrode conductor ③. Adopting groove-buried gate technology; can effectively reduce the resistance value of the electrode conductor resistance, thereby achieving the purpose of reducing the series resistance; however, 1. Using better conductive materials will increase the manufacturing cost rapidly, and The reduced resistance resistance is limited; 2. For the current common solar cells, the basic requirement is that the electrode conductor element should be as narrow as possible, so as to maximize the light-receiving area of the light incident surface, and the ratio of the light incident surface covered by the electrode conductor element The smaller the battery, the better the performance of the battery. Generally, the area of the electrode conductor element does not exceed 10% of the total area of the solar cell; Some series resistors, but also increased manufacturing costs, and the current production technology is not enough to support large-scale batch production.

It has now been found that using simple technologies such as widening the width of the electrode conductor element can obtain a concentrator solar cell with a relatively small series resistance, but the electrode element is widened, and the area of the cell covered by the electrode is also increased, which has not been obtained. Good results.

Contents of the invention

The invention relates to a method for reducing the resistance value of the series resistance of a concentrator solar cell having a body of doped semiconducting material, the body having two main opposing faces forming a solderable electrode conductor element The light incident surface and the back of a weldable electrode conductor element, wherein, the light incident surface and the back of the concentrator solar cell are respectively equipped with weldable electrode conductor elements, and the light incident surface and the back weldable electrode conductor element are just arranged on the concentrating solar cell. corresponding relatively long sides of the photocell; the method comprising the steps of:

a) providing a doped semiconductor body having p/n junctions;

b) Make weldable electrode conductor elements on the light incident surface of the semiconductor body. The specifications are: the width of the weldable electrode conductor elements is 0.2mm-0.8mm, the length of the electrode conductor elements is equal to the width of the semiconductor body, and two adjacent weldable electrodes The distance between conductor elements is 1.0mm-4mm, and there is no conductor connection between two adjacent weldable electrode conductor elements;

c) Make weldable electrode conductor elements on the back of the semiconductor body, the specifications are: the width of the weldable electrode conductor elements is 0.2mm-0.8mm, the length of the weldable electrode conductor elements is equal to the width of the semiconductor body, and two adjacent electrode conductor elements The distance between them is 1.0mm-4mm, and its position is exactly staggered from the electrode conductor elements on the light incident surface, and the staggered positions of all weldable electrode conductor elements are guaranteed to be consistent;

d) making an aluminum layer at other positions on the back of the semiconductor body as a back field;

e) making an anti-reflection film on the light incident surface;

f) Metallization and sintering of electrode conductor elements;

g) Using a laser scribing machine to scribe along the staggered positions of the upper and lower weldable electrode conductor elements to form an independent concentrator solar cell with low series resistance.

Of course, the production sequence of the above steps (b, c, d, e) can be relatively adjusted without affecting the final effect of the concentrating solar cell.

Furthermore, the invention relates to concentrator solar cells comprising a doped semiconductor body having two main opposing faces forming a light entrance face with a solderable electrode conductor element and a solderable electrode The back side of the conductor element, wherein, the light incident surface and the back side of the concentrator solar cell are respectively equipped with weldable electrode conductor elements, the width of the weldable electrode conductor element is 0.2mm-0.8mm, and the length of the weldable electrode conductor element is equal to that of the semiconductor The width of the main body is the same, and the light incident surface and the electrode conductor elements on the back are just placed on the relatively long sides of the concentrator cell. The width of the semiconductor material of the battery is the same, and the actual use length is determined according to the actual needs.

In the concentrating solar cell manufactured by the above method, one side of the light incident surface of the semiconductor body and the other side of the back will respectively form a weldable electrode conductor element with a width equal to the length of the concentrator solar cell, and the weldable electrode conductor element The maximum length is only 0.8mm, that is, the conductive cross-sectional area of the weldable electrode conductor element = the width of the semiconductor body material × the height of the electrode conductor element, so its resistance value is much smaller than that of the electrode conductor element of ordinary solar cells. , the resistance of the electrode conductor element is almost negligible, which effectively reduces the overall series resistance of the concentrating solar cell; The weldable electrode conductor components are welded together, which belongs to the series connection mode, that is, another concentrating solar cell covers the electrode conductor component of the previous concentrating solar cell. From the surface, the sunlight shining on the concentrating solar cell The incident surface of light is not blocked by any object, and all of it is absorbed by the concentrating solar cell, which makes full use of sunlight resources and improves the power generation efficiency of the concentrating solar cell.

Description of drawings:

Fig. 1 Various projection plane diagrams of concentrating solar cells;

Fig. 1 (a) is the light incident front view of concentrator solar cell, light incident surface 4 and front weldable electrode conductor element 3; Fig. 1 (b) is the back view of concentrator solar cell, back 2 and back weldable electrode Conductor element 1, wherein the back side 2 has been vapor-deposited with a layer of insulating film material; Figure 1 (c) is the side state of two concentrator solar cells connected together before scribing, and the front side can be soldered. The electrode conductor element 3 and the back side can be The welding electrode conductor element 1 is just staggered at position 5, and the laser scribing machine cuts the concentrating solar cell at the staggered position 5 to form two independent concentrating solar cells; Figure 1(d) is after scribing In the side state where two concentrating solar cells are connected in series, the front weldable electrode conductor element 3 of the first concentrating solar cell and the back weldable electrode conductor element 1 of the second concentrating solar cell have been firmly welded on the At the same time, since the width of the conductive element of the weldable electrode is very wide, which is equivalent to the width of the semiconductor material, and the length is very short, the length is 0.2mm-0.8mm, so the resistance of the weldable electrode conductor is negligible, and the first concentrated solar energy The weldable electrode conductive element 3 on the light incident surface of the battery is covered by the second concentrating solar cell. Fig. 1 (e) is a plan view of 10 concentrating solar cells connected in series. Seen from the surface, only the concentrating solar cell light The incident surface 4 is exposed to sunlight without any electrode conductor element covering, and the sunlight resource is utilized 100%, which improves the power generation efficiency of the concentrating solar cell.

Implementation method:

The present invention relates to improvements in concentrator solar cells based on bodies of doped semiconductor material, such as monocrystalline silicon wafers. The invention also relates to improvements in the method of preparing the solderable electrode-conductor elements of such concentrator solar cells.

According to a preferred embodiment, the concentrating solar cell is made of doped silicon as an active semiconductor device, and a conventional Czochralski monocrystalline silicon wafer with a square shape of 125 mm x 125 mm and a thickness of 220 μm is used. This wafer can be purchased in the market obtained on

Through conventional processes such as etching, structuring, and cleaning the wafer, and then the light incident surface of the silicon wafer is re-diffused at 800-900°C by doping with a phosphorus compound, such as POCl ₃ , to make it n-type and form a poly The basic p/n node of the active component of the solar cell has a surface resistance value of about 30Ω/□.

Apply the solderable silver paste on the light incident surface of the doped semiconductor body through a mask to form several solderable electrodes with a width of 0.5mm, a clearance of 2mm between any two soldering electrode conductor elements, and a length of 125mm. conductor elements, and there is no conductor connection between two adjacent weldable electrode conductor elements.

Similarly, through a mask, solderable silver paste is applied to the back of the doped semiconductor body to form several solderable electrode conductor elements with a width of 0.5mm, an interval of 2mm between the two, and a length of 125mm. The positions of the solderable electrode conductor elements on the back surface of the semiconductor body are just staggered from those on the light incident surface, and the staggered positions of all the weldable electrode conductor elements are consistent.

On the back side of the doped semiconductor body where no silver paste is applied, a layer of aluminum is evaporated to generate a back electric field.

The commonly used high-temperature sintering process and other measures are applied to the above materials, so that the silver paste is firmly and reliably connected to the silicon surface, and a back electric field is formed on the back.

A layer of anti-reflection film is deposited on the light incident surface of the concentrating solar cell by using a conventional process method.

Use a laser scribing machine to slit along the staggered part of the weldable electrode conductor element on the light incident surface and the back weldable electrode conductor element to form an independent concentrating solar cell with a length of 125mm and a width of 2.5mm with low series resistance.

The semiconductor material body used in concentrating solar cells not only contains doped silicon, but also any other semiconductor materials. Examples of other semiconductor materials are gallium arsenide, indium phosphide, copper indium selenide, germanium and zinc oxide.

The weldable electrode conductor component is the medium for free electron flow, and it is the place where the upper surface of one concentrating solar cell is welded to the lower surface of another concentrating solar cell in the series connection mode of concentrating solar cells, and the high conductivity of the component must be ensured Performance and high weldability, the metal materials used are mainly aluminum, silver, titanium, nickel, etc., or the comprehensive application of these metals.

Claims (9)

1. A method for reducing the resistance value of the series resistance of a concentrator solar cell having a body of doped semiconductor material, the body having two main opposing faces forming a solar cell having a solderable electrode conductor element The incident surface and the back of a weldable electrode conductor element, wherein the light incident surface and the back of the concentrator solar cell are respectively equipped with weldable electrode conductor elements, and the light incident surface and the back weldable electrode conductor element are just placed on the concentrator cell. corresponding sides; the method comprises the steps of: a) providing a doped semiconductor body having p/n junctions; b) Make weldable electrode conductor components on the light incident surface of the doped semiconductor body, and its specifications are: weldable electric The width of the pole conductor element is 0.2mm-0.8mm, the length of the weldable electrode conductor element is equal to the width of the semiconductor body, the distance between two adjacent weldable electrode conductor elements is 1.0mm-4mm, and the distance between two adjacent weldable electrode conductor elements There is no conductor connection between them; c) Weldable electrode conductor elements are made on the back of the doped semiconductor body. The distance between the welding electrode conductor elements is 1.0mm-4mm, and its position is just staggered from the electrode conductor elements on the light incident surface, and the staggered positions of all weldable electrode conductor elements are guaranteed to be consistent; d) forming an aluminum layer at other positions on the backside of the doped semiconductor body as a backside field; e) making an anti-reflection film on the light incident surface; f) Metallization and sintering of electrode conductor elements; g) Use a laser scribing machine to scribe along the staggered positions of the weldable electrode conductor elements on the light incident surface of the doped semiconductor material and the weldable electrode conductor elements on the back side, and finally form an independent concentrator solar cell with low series resistance; 2. The method according to claim 1, wherein the production sequence of steps (b, c, d, e) can be adjusted relatively without affecting the final effect of the concentrated solar cell. 3. The method according to claim 1, 2, wherein the body of semiconductor material comprises one of the group consisting of silicon, gallium arsenide, indium phosphide, copper indium selenide, germanium and zinc oxide. 4. The method according to claim 1, 2, 3, wherein the metal materials used for the weldable electrode conductor components mainly include aluminum, silver, titanium, nickel, etc., or a comprehensive application of these metals. 5. A concentrator solar cell comprising a doped semiconductor body having two main opposing faces forming a light entrance face with a solderable electrode conductor element and a solderable electrode conductor element The back side, and the doped semiconductor material body also has a plurality of side faces between the main opposite sides, wherein the light incident side and the back side of the concentrator solar cell are respectively equipped with weldable electrode conductor elements, and the width of the weldable electrode conductor element is It is 0.2mm-0.8mm. The length of the weldable electrode conductor element is equal to the width of the semiconductor body. The weldable electrode conductor element on the light incident surface and the back is just placed on the corresponding longer sides of the concentrator cell. The entire concentrator cell The width is 1.2mm-4.8mm, and the maximum length is equal to the width of the semiconductor material. The actual length is determined according to actual needs. 6. The concentrated solar cell according to claim 5, wherein the semiconductor material body comprises one of the group consisting of silicon, gallium arsenide, indium phosphide, copper indium selenide, germanium and zinc oxide. 7. The concentrated solar cell according to claims 5 and 6, wherein the metal materials used for the weldable electrode conductor elements mainly include aluminum, silver, titanium, nickel, etc., or a comprehensive application of these metals. 8. Concentrating solar cell according to claim 5, 6, 7, wherein the body of semiconductor material is a doped wafer. 9. Concentrating solar cells obtained by the method of any one of claims 1, 2, 3, and 4.

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