CN105261662B - A kind of solar cell chip with diffusion junctions bypass diode - Google Patents

Abstract

The invention discloses a solar cell chip with a diffused junction bypass diode, which comprises from top to bottom: a front electrode, a solar cell photoelectric conversion layer including an emission region and a base region, and mutually isolated first and second back electrodes. , the lower surface of the base region has a diffusion junction in a local area, the diffusion junction is located on one side of the battery chip, the first back electrode covers but does not exceed the part of the base region that has not undergone surface diffusion, and the second back electrode Cover but not exceed the surface of the diffusion junction. The bypass diode designed in the present invention is used to protect the adjacent battery slices in the battery string, the chip process is simple, and it does not need to undergo multiple diffusion and etching to form a bypass diode mechanically isolated from the photoelectric conversion layer of the battery; the bypass diode is located on the back of the battery slice , does not occupy the illuminated area of the battery surface; the base region also serves as the positive (or negative) of the photoelectric conversion layer and the bypass diode, reducing power loss.

Description

A solar cell chip with diffused junction bypass diode

technical field

The invention relates to a solar cell chip with a diffusion junction bypass diode, belonging to the field of semiconductor optoelectronic devices and technologies.

Background technique

Solar cells are one of the most important clean energy sources. Due to the dispersion of solar energy, a large-scale power supply system must use a large number of solar cells for series-parallel connection. The resulting problem is that once one of the cells in the series-parallel network If the cell fails, the power generation of the entire network will drop significantly; at the same time, the failed cell is equivalent to a load, forming a so-called hot spot, which will lead to irreversible damage to the failed cell under long-term load, that is, the irreversible efficiency of the entire network. Attenuation, or even the failure of the entire network. Therefore, a reverse diode is usually connected in parallel to each cell, which is called a bypass diode. Under normal working conditions, the bypass diode is connected to the cell in reverse, which is equivalent to an open circuit; and when a cell fails, it is not working. state, the bypass diode is forward connected in series with the adjacent cell, and conducts at a lower voltage drop, ensuring the normal operation of the entire network. However, adding bypass diodes, on the one hand, increases the cost and the complexity of the packaging process. On the other hand, for non-concentrating battery systems, such as space application batteries, the bypass diodes will occupy a large part of the area due to the close arrangement of the cells. The use of sunlight is reduced, and for concentrated photovoltaic systems, in some battery systems that also require close arrangement, such as cogeneration battery systems, it is impossible to configure a bypass diode for each cell. At present, in some solar cells, the bypass diode is integrated on the battery sheet, that is, a part of the area is isolated in the battery sheet to form a diode, which simplifies the battery packaging process, and also reduces the illuminated area occupied by the bypass diode to a certain extent. However, this method still fails to completely avoid the waste of the illuminated area, and more importantly, this method is only applicable to the case of a small photo-generated current, because the current that the bypass diode allows to pass is proportional to its p-n junction area, The larger the photogenerated current, the larger the area of the bypass diode is required. For example, in a concentrating cell, the bypass diode will occupy more than 30% of the illuminated area, which is obviously not applicable.

Contents of the invention

In view of the above problems, the present invention discloses a solar cell chip with diffused junction bypass diodes. The solar cell chip includes from top to bottom: a front electrode, a solar cell photoelectric conversion layer including an emitter region and a base region, and mutually isolated The first back electrode and the second back electrode, the lower surface of the base region has a local diffusion junction, the diffusion junction is located on one side of the battery chip, the first back electrode covers but does not exceed the base region without surface diffusion part, the second back electrode covers but does not exceed the surface of the diffusion junction.

Preferably, the front electrode is the light-receiving surface electrode, which is a grid-shaped metal electrode or a transparent conductive layer, and includes at least one connecting pad;

Preferably, a solar cell substrate is provided, and an emission region is formed on the upper surface of the solar cell substrate by a diffusion process, and the undiffused part below the emission region is used as a base region;

Preferably, the diffusion junction in the local area is located on the lower surface of the base region, and is formed by the same diffusion as the emission region;

Preferably, the solar cell chip is a multi-junction compound cell, comprising an epitaxial substrate, and the photoelectric conversion layer is grown on the epitaxial substrate by MOCVD or MBE;

Preferably, the local region diffusion junction is located on the lower surface of the epitaxial substrate of the multi-junction compound solar cell, and the epitaxial substrate can only serve as a substrate, or it can be a sub-cell at the bottom of the multi-junction cell, and the epitaxial substrate The bottom polarity is the same as the base region;

Preferably, the area of the diffusion junction in the local area is determined according to the size of the photogenerated current, preferably, the current density passing through the diffusion junction is not greater than 70mA/mm ² ;

Preferably, the first back electrode covers but does not exceed the undiffused base region;

Preferably, the second back electrode is located in the central region of the diffusion junction in the local area, and does not exceed the range of the diffusion junction.

The bypass diode designed in the present invention is used to protect adjacent battery slices in the battery string, and its advantages include:

(1) For silicon cells, the diffusion junction and emitter region of the bypass diode are formed by one diffusion; for compound multi-junction cells, only one diffusion is required to form the bypass diode, and the bypass diodes of the above two solar cells are manufactured. There is no need to undergo an etching process. Therefore, the structure and manufacturing process of a solar cell chip proposed by the present invention are simple, and there is no need to undergo multiple diffusions and etchings to form bypass diodes that are mechanically isolated from the photoelectric conversion layer of the battery;

(2) The base area serves as the anode (or cathode) of the photoelectric conversion layer and the bypass diode at the same time, and the bypass current directly enters the bypass diode from the base area, reducing power loss;

(3) The bypass diode of the present invention is located on the back of the cell, and does not occupy the illuminated area of the cell surface.

Description of drawings

FIG. 1 schematically provides a silicon solar cell substrate or a multi-junction compound solar cell epitaxial wafer.

Fig. 2 schematically shows that through primary diffusion, an emission region is formed on the upper surface of the solar cell substrate, and a diffusion junction diode is formed on a local area of the lower surface of the solar cell substrate.

FIG. 3 is a top view of the back of FIG. 2 .

Fig. 4 schematically shows the deposition of the first and second back electrodes.

FIG. 5 is a top view of the back of FIG. 4 .

Figure 6 illustrates the deposition of a front electrode on the surface of the emitter region.

FIG. 7 is a front top view of FIG. 6 .

Fig. 8 schematically shows a connection mode of solar cell chips with diffused junction bypass diodes to form a cell string, which is a cross-sectional view.

FIG. 9 schematically shows a connection method of solar cell chips with diffused junction bypass diodes to form a cell string, which is a top view from the front.

FIG. 10 schematically shows a connection method of solar cell chips with diffused junction bypass diodes to form a cell string, which is a top view from the back.

In the figure: 001: solar cell substrate; 001a: emitter region; 001b: base region; 002: diffusion junction bypass diode; 003: first back electrode; 004: second back electrode; 005: front electrode.

detailed description

The present invention will be further described below in conjunction with the examples, but the protection scope of the present invention should not be limited thereby.

Example 1

(1) As shown in Figure 1, a silicon solar cell substrate 001 is provided, which is p-type;

(2) As shown in Figures 2 and 3, phosphorus is diffused on the upper surface and the local lower surface of the silicon solar cell substrate 001 to form an n-type emitter region 001a and a diffusion junction bypass diode 002 in a local area on the back, respectively. The anode (p-type layer) of the junction bypass diode is also used as the base region 001b, the emitter region 001a and the base region 001b form the photoelectric conversion layer of the solar cell, and the n-type layer formed by diffusion is the cathode of the diffused junction bypass diode 002, located at The area of one side of the battery chip is determined according to the size of the photogenerated current of the solar battery chip, so that the current density passing through the diffusion junction bypass diode 002 does not exceed 70mA/mm ² ;

(3) As shown in Figures 4 and 5, deposit the first back electrode 003 and the second back electrode 004, wherein the first back electrode 003 covers but does not exceed the part of the base region 001b that has not undergone surface diffusion, and serves as the positive electrode of the battery chip. The second back electrode 004 covers but does not exceed the surface of the diffused junction bypass diode 002, serving as the cathode of the diffused junction bypass diode 002;

(4) As shown in Figures 6 and 7, prepare the front electrode 005, which includes at least one connecting pad and several grid electrodes, to obtain a solar cell chip;

(5) As shown in Figures 8 to 9, connect the aforementioned solar cell chips in series through the connection strip, and then connect the negative pole of the diffusion junction bypass diode 002 to the positive pole 003 of the adjacent battery chip. When one of the solar cell chips fails , the current on the battery string will directly flow into the anode 003 of the failed chip through the diffusion junction bypass diode 002 of the upper chip of the failed chip, so as to achieve the purpose of protecting the failed chip.

Example 2

(1) As shown in Figure 1, a silicon solar cell substrate 001 is provided, which is n-type;

(2) As shown in Figures 2 and 3, boron is diffused on the upper surface and the local lower surface of the silicon solar cell substrate to form a p-type emitter region 001a and a diffused junction bypass diode 002 in a local area on the back, respectively. The cathode (n-type layer) of the bypass diode 002 serves as the base region 001b at the same time, the emitter region 001a and the base region 001b form the photoelectric conversion layer of the solar cell, and the p-type layer formed by diffusion is the anode of the diffusion junction bypass diode 002, which is located On one side of the chip, the area is determined according to the size of the photogenerated current of the solar cell chip, so that the current density passing through the diffusion junction bypass diode 002 does not exceed 70mA/mm ² ;

(3) As shown in Figures 4 and 5, deposit the first back electrode 003 and the second back electrode 004 that are isolated from each other, wherein the first back electrode 003 covers but does not exceed the part of the base region 001b that has not undergone surface diffusion, as a battery chip Negative electrode, the second back electrode 004 covers but does not exceed the surface of the diffused junction bypass diode 002, as the positive electrode of the diffused junction bypass diode 002;

(4) As shown in FIGS. 6 and 7 , prepare the front electrode 005 , which includes at least one connection pad and several grid wire electrodes, to obtain a solar cell chip.

Example 3

(1) As shown in Figure 1, a compound solar cell epitaxial wafer is provided, the photoelectric conversion layer of which is a GaInP/InGaAs/Ge triple-junction cell, the base region of each subcell is p-type, and the emitter region is n-type, in which Ge The epitaxial substrate of the solar cell is also used as the third sub-cell, and the Ge substrate is p-type;

(2) As shown in Figures 2 and 3, phosphorus is diffused in a local area on the back of the Ge substrate to form a p/n diffusion junction, which is used as the diffusion junction bypass diode 002 and is located on one side of the battery chip. The area of the diffusion junction is based on the solar The photo-generated current of the battery chip depends on the magnitude of the current density passing through the diffusion junction bypass diode 002 not exceeding 70mA/mm ² ;

(3) As shown in Figures 4 and 5, deposit the first back electrode and the second back electrode isolated from each other, where the first back electrode covers but does not exceed the part of the base area that has not undergone surface diffusion, as the positive electrode of the battery chip, and the second The back electrode covers but does not exceed the surface of the diffusion junction bypass diode 002, and serves as the cathode of the diffusion junction bypass diode 002;

(4) As shown in FIGS. 6 and 7 , prepare the front electrode, which includes at least one connection pad and several grid electrodes.

Example 4

(1) As shown in Figure 1, a GaInP/InGaAs/GaAs double-junction solar cell epitaxial wafer is provided, the photoelectric conversion layer is a GaInP/InGaAs double-junction solar cell, and the sub-cell base area is p-type, and the emitter area is n-type, where GaAs is only used as an epitaxial substrate and is p-type;

(2) As shown in Figures 2 and 3, a p/n diffusion junction is formed by diffusion in a local area on the back of the GaAs substrate. As a diffusion junction bypass diode 002, it is located on one side of the battery chip. The area of the diffusion junction depends on the solar cell chip The magnitude of the photogenerated current is determined so that the current density of the bypass diode 002 through the diffusion junction does not exceed 70mA/mm ² ;

(3) As shown in Figures 4 and 5, deposit the first back electrode and the second back electrode isolated from each other, where the first back electrode covers but does not exceed the part of the base area that has not undergone surface diffusion, as the positive electrode of the battery chip, and the second The back electrode covers but does not exceed the surface of the diffusion junction bypass diode 002, and serves as the cathode of the diffusion junction bypass diode 002;

(4) As shown in FIGS. 6 and 7 , prepare the front electrode, which includes at least one connection pad and several grid electrodes.

Claims (7)

1. a kind of solar cell chip with diffusion junctions bypass diode, the solar cell chip includes from top to bottom：Just Face electrode, the solar cell photoelectric conversion layer including launch site and base and the first mutually isolated backplate, second back of the body Face electrode, the base lower surface has a regional area diffusion junctions, and the diffusion junctions pass through with a divergent contour with launch site Into the diffusion junctions are located at the side of battery chip, and first backplate is covered but do not carry out surface expansion without departing from base Scattered part, second backplate is covered but without departing from the diffusion junctions surface.

2. a kind of solar cell chip with diffusion junctions bypass diode according to claim 1, it is characterised in that：Institute Front electrode i.e. smooth surface electrode is stated, it is metal electrode of the grating or transparency conducting layer, comprising an at least connect band pad.

3. a kind of solar cell chip with diffusion junctions bypass diode according to claim 1, it is characterised in that：Carry For a solar cell substrate, launch site, the launch site lower section are formed by diffusion technique in the solar cell substrate upper surface The part do not spread is used as base.

4. a kind of solar cell chip with diffusion junctions bypass diode according to claim 1, it is characterised in that：Institute Solar cell chip is stated for multijunction compound solar cell, comprising an epitaxial substrate, and using MOCVD or MBE in epitaxial substrate Upper growth photoelectric conversion layer.

5. a kind of solar cell chip with diffusion junctions bypass diode according to claim 4, it is characterised in that：Institute Regional area diffusion junctions are stated positioned at the multijunction compound solar cell epitaxial substrate lower surface, the epitaxial substrate functions only as lining Bottom, or as the knot battery of multijunction cell bottommost one, and the epitaxial substrate polarity is identical with base.

6. a kind of solar cell chip with diffusion junctions bypass diode according to claim 1, it is characterised in that：Institute State regional area diffusion junction area to determine according to photogenerated current size, 70mA/mm is not more than by diffusion junctions current density²。

7. a kind of solar cell chip with diffusion junctions bypass diode according to claim 1, it is characterised in that：Institute The second backplate is stated positioned at the regional area diffusion junctions central area, and without departing from diffusion junctions scope.