TWM511126U - Solar cell with cell edge collection structure - Google Patents

Abstract

A solar cell includes a substrate having a front surface and a rear surface, a front electrode on the front surface, an annular AlSi layer disposed along perimeter of the substrate on the rear surface, a passivation layer on the rear surface, and a rear electrode on the passivation layer. The rear electrode includes a Si-rich electrode portion that penetrates through the passivation to contact the annular AlSi layer. The AlSi layer and/or the Si-rich electrode portion has a first edge and a second edge. The second edge is between the first edge and the perimeter. At least part of the second edge is not parallel with the perimeter.

Description

Solar cell with crystal edge collecting structure

This creation relates to the field of solar cell technology, and in particular to a Passived Emitter and Rear Contact (PERC) solar cell with a Cell Edge Collection (CEC) structure.

The solar cell illuminates the semiconductor substrate by incident light, and generates an electron hole pair at the PN junction surface thereof, and collects the photocurrent through the front surface (or the light receiving surface) and the back surface electrode respectively before the electron hole pair is recombined. .

Passivated emitter back contact (PERC) solar cells utilize a passivation layer (usually a thin layer of aluminum oxide) formed on the back side of the solar cell to reduce recombination of electron-hole pairs and can be combined with anti-reflective coatings. Light is reflected back into the solar cell to increase battery efficiency.

It is known that the four corners or crystal edge portions of the solar cell are prone to high impedance problems, which is more pronounced as the opening ratio of the back passivation layer is smaller, and causes a decrease in the fill factor (FF). Increasing the open cell ratio of the back passivation layer reduces the effective area of the passivation layer and affects the electrical characteristics of the battery, for example, the open circuit voltage V _OC and the short circuit current I _SC decrease.

It can be seen that there is still a need in the art for an improved solar cell technology to address the deficiencies and shortcomings of the prior art described above.

The purpose of this creation is to provide an improved solar cell that can improve cell efficiency with lower impedance and higher fill factor.

In order to achieve the above object, the present invention provides a solar cell comprising a substrate having an opposite first surface and a second surface; a front electrode disposed on the first surface; an aluminum-bismuth alloy layer, the aluminum germanium The alloy layer is a ring-shaped aluminum-bismuth alloy layer disposed on the second surface along the edge of the substrate; a passivation layer disposed on the second surface; and a back electrode on the passivation layer, the back electrode including a ruthenium-rich electrode portion, the ytterbium-rich electrode portion is in contact with the aluminum-niobium alloy layer through the passivation layer, wherein the aluminum-niobium alloy layer and/or the yttrium-rich electrode portion has a first edge and a second edge, the second edge being located between the first edge and the perimeter, wherein at least a portion of the second edge is non-parallel to the perimeter of the substrate.

The above described objects, features and advantages of the present invention will become more apparent from the following description. However, the following preferred embodiments and drawings are for illustrative purposes only and are not intended to limit the present invention.

1‧‧‧Solar battery

22‧‧‧Doped emitter layer

23‧‧‧Oxide layer

24‧‧‧ Positive anti-reflection coating

30‧‧‧Front electrode

40‧‧‧Back electrode

42‧‧‧Electrium-rich electrode

421‧‧‧Aluminum-niobium alloy layer

422‧‧‧ first edge

423‧‧‧ second edge

42a‧‧‧ wave contour

42b‧‧‧Sawtooth profile

42c‧‧‧ city-like outline

42d‧‧‧Hollow grille profile

42e‧‧‧ hollow grille profile

42f‧‧‧ hollow pyramid profile

43‧‧‧Regional back surface electric field

44‧‧‧Back contact electrode

52‧‧‧ Passivation layer

60‧‧‧Back protective layer

100‧‧‧Semiconductor substrate

100a‧‧‧ first surface

100b‧‧‧ second surface

Around 101‧‧

142‧‧‧ hollow area

FIG. 1 is a schematic cross-sectional view of a solar cell according to the present embodiment.

2 to 7 illustrate an electrode structure provided on the second surface of the solar cell.

Please refer to FIG. 1 , which is a schematic cross-sectional view of a solar cell according to an embodiment of the present invention. As shown in FIG. 1, the solar cell 1 includes a semiconductor substrate 100 having a first surface 100a and a second surface 100b opposite to the first surface 100a. According to the present embodiment, the solar cell 1 is a Passivated Emitter and Rear Contact (PERC) solar cell. The semiconductor substrate 100 may be an N-type or P-type single crystal germanium substrate or a polycrystalline germanium substrate, but is not limited thereto. The first surface 100a and the second surface 100b may have a concave-convex structure formed after the surface roughening treatment. The first surface 100a may further include an N-type or P-type dopant emitter layer 22, an oxide layer 23, such as cerium oxide, and at least one front anti-reflective coating 24. The doped emitter layer 22 is electrically opposite to the semiconductor substrate 100. For example, the semiconductor substrate 100 is a P-type single crystal germanium substrate, doped emitter layer 22 is N type. The doped emitter layer 22 may be a generally doped emitter layer or a selectively doped emitter layer having a thickness of 5 to 10 nanometers (nm), preferably 7 nm. The surface passivation of the single crystal germanium substrate can be improved, and the Potential Induced Degradation (PID) can be reduced.

In other embodiments, when the semiconductor substrate 100 is a polycrystalline germanium substrate, the doped emitter layer 22 may not be provided with an oxide layer 23. According to an exemplary embodiment, the front anti-reflective coating 24 may include tantalum nitride, but is not limited thereto.

The first surface 100a may further include at least one front surface electrode 30. For example, a conductive material is disposed on the first surface 100a of the solar cell 1 by a conventional screen printing method, and then formed by sintering. Front electrode 30. In other embodiments, the front electrode 30 may also be formed by other means such as an electroplating method, but is not limited thereto.

According to an exemplary embodiment, the front electrode 30 may be etched through the front anti-reflective coating 24 while being in contact with the doped emitter layer 22. In other embodiments, the front anti-reflective coating 24 is a patterned anti-reflection coating. The reflective coating, the conductive material may be in contact with the doped emitter layer 22 through the pattern of the front anti-reflective coating 24, and then sintered to form the front electrode 30. The pattern of the front anti-reflective coating 24 refers to a penetrating front anti-reflective coating. 24 opening.

The second surface 100b includes a back electrode 40 and a back contact electrode 44. According to the present embodiment, the back electrode 40 contains aluminum metal, and the back contact electrode 44 contains silver, aluminum or other conductive metal, but is not limited thereto. A passivation layer 52, such as an aluminum oxide (AlOx) layer, having a thickness of 1 to 20 nm and a refractive index (n) of between 1.6 and 1.7 is provided between the back surface electrode 40 and the semiconductor substrate 100, but is not limited thereto. In other embodiments, the thickness of the passivation layer 52 may be 1 nm, 5 nm, 10 nm, 15 nm or 20 nm, and the refractive index (n) is 1.6, 1.61, 1.62, 1.63, 1.64, 1.65. , 1.66, 1.67, 1.68, 1.69 or 1.7. The passivation layer 52 on the second surface 100b includes at least one first opening to expose a portion of the semiconductor substrate 100, and the aluminum-containing metal back electrode 40 extends into the first opening and forms a rich in the first opening The electrode portion 42 containing ruthenium, wherein the ruthenium-rich electrode portion 42 has a ruthenium content higher than that of the ruthenium-rich electrode portion 42 and is rich in The electrode portion 42 of the crucible may include an aluminum-bismuth alloy layer 421. A region back surface field (Local BSF) 43 is formed at the boundary between the electrode portion 42 rich in germanium and the semiconductor substrate 100. The first opening may be a continuous linear opening, a dotted-shaped opening, a dot-shaped opening, or a combination thereof, but is not limited thereto.

According to an exemplary embodiment, there is a backside protective layer 60 between the backside electrode 40 and the passivation layer 52. The back protective layer 60 may be a single layer or a multilayer film structure, such as a single layer of tantalum nitride or hafnium oxynitride layer, or a plurality of layers of tantalum nitride, hafnium oxynitride or a combination thereof, wherein the back protective layer 60 has a relative a second opening of the first opening.

The back surface electrode 40 is in contact with the semiconductor substrate 100 through the first opening and the second opening, and a germanium-rich electrode portion 42 is formed in the first opening and the second opening.

Please refer to FIGS. 2-7, which illustrate a Cell Edge Collection (CEC) structure layout disposed on the second surface of the solar cell. As shown in FIG. 2, a plurality of parallel region back surface electric fields (Local BSF) 43 are disposed in an approximately central region on the second surface 100b of the semiconductor substrate 100, and a plurality of strips are provided on the electric field on the back surface of the region. A parallel aluminum-bismuth alloy layer 421 is provided along the periphery 101 of the semiconductor substrate 100 with an annular aluminum-bismuth alloy layer 421 disposed around the region in the central region facing away from the surface electric field 43. An annular crucible-rich electrode portion 421 is provided on the annular aluminum-bismuth alloy layer 421, and the antimony-rich electrode portion 42 is in contact with the aluminum-bismuth alloy layer 421, and the aluminum-bismuth alloy layer is disposed in the central region. A plurality of parallel enthalpy-rich electrode portions 42 are correspondingly provided on the 421. In other embodiments, the aluminum-niobium alloy layer 421 and the region-back surface electric field 43 in the central region may be in a continuous line shape, a dotted line shape, a dot shape, or a combination thereof, and the arrangement manner may also be set in a non-parallel manner, for example, the center. The region includes a combination of a partially parallel dotted aluminum-bismuth alloy layer 421 and a portion of the non-parallel point-like aluminum-bismuth alloy layer 421.

According to an exemplary embodiment, the aluminum-bismuth alloy layer 421 and/or the germanium-rich electrode portion 42 has a first edge 422 and a second edge 423, and the second edge 423 is located at the first edge 422 and the periphery of the semiconductor substrate 100. Between 101, at least a portion of the second edge 423 is non-parallel to the periphery 101 of the semiconductor substrate 100.

In FIG. 2, an annular ruthenium-rich electrode portion 42 and/or an aluminum-niobium alloy layer 421 having a convex shape near the second edge 423 of the periphery 101 of the solar cell, for example, not parallel to the periphery 101 The wave profile 42a constitutes the electrode structure of the present invention and can increase the fill factor (FF). Fig. 2A is a schematic cross-sectional view taken along line II-I' in Fig. 2, and Fig. 2B is a schematic cross-sectional view taken along line II-II' in Fig. 2. As can be seen from FIGS. 2A and 2B, the second edge 423 has a wave profile 42a that is not parallel to the perimeter 101, so that the second edge 423 of the electrode portion 42 rich in germanium has a different height from the perimeter 101 of the solar cell. The distances d1 and d2, in this case, d1 is smaller than d2.

The structure of the back surface electric field 43 and the ytterbium-rich electrode portion 42 in the above region is as shown in FIG. 1, and the electrode portion 42 rich in ruthenium is in contact with the aluminum-bismuth alloy layer 421 through the passivation layer 52 and the back surface protective layer 60. Other details will not be described again.

The annular ruthenium-rich electrode portion 42 and/or the aluminum-niobium alloy layer 421 may have other contours near the second edge 423 of the periphery 101 of the solar cell.

For example, as shown in FIG. 3, an annular crucible-rich electrode portion 42 and/or an aluminum-bismuth alloy layer 421 having a second edge 423 near the periphery 101 of the solar cell has a zigzag profile that is not parallel to the perimeter 101. 42b. The zigzag profile 42b may be disposed only along a portion of the perimeter 101 of the solar cell, but is not limited thereto.

As shown in Fig. 4, a ring-shaped ytterbium-rich electrode portion 42 and/or an aluminum-niobium alloy layer 421 having a battlement-shaped profile 42c adjacent to the second edge 423 of the periphery 101 of the solar cell. The above-described ridge-like profile 42c may be disposed only along a portion of the perimeter 101 of the solar cell, but is not limited thereto. In this example, the above-described battlement profile 42c is disposed along opposite side edges of the solar cell.

As shown in Fig. 5, the annular crucible-rich electrode portion 42 and/or the aluminum-bismuth alloy layer 421 has a hollow grid-like profile 42d adjacent to the second edge 423 of the periphery 101 of the solar cell. The hollow grid-like profile 42d in Fig. 5 separates a single hollow region 142, and an aluminum-bismuth alloy is not formed in the hollow region 142.

As shown in Fig. 6, the annular crucible-rich electrode portion 42 and/or the aluminum-bismuth alloy layer 421 has a continuous hollow grid-like profile 42e adjacent the second edge 423 of the periphery 101 of the solar cell. Different from the hollow grid-like profile 42d of Fig. 5, the continuous hollow grid-like profile 42e of Fig. 6 can be adjacent to the two hollow regions 142. An aluminum-bismuth alloy is not formed in the hollow region 142.

As shown in Fig. 7, an annular crucible-rich electrode portion 42 and/or an aluminum-bismuth alloy layer 421 having a hollow pyramid-like profile 42f adjacent to the second edge 423 of the periphery 101 of the solar cell. An aluminum-bismuth alloy is not formed in the hollow region 142 surrounded by the respective hollow pyramid-shaped contours 42f. The hollow pyramid-shaped profile 42f may be disposed only along a portion of the perimeter 101 of the solar cell, but is not limited thereto. In this example, the hollow pyramid-like profile 42f is disposed along opposite side edges of the solar cell.

In other embodiments, the aluminum-bismuth alloy layer 421 also has a first edge and a second edge, wherein the second edge is located between the first edge and the perimeter, wherein at least a portion of the second edge is opposite the substrate The perimeter is not parallel, ie the second edge has a convex contour. In still other embodiments, the aluminum tantalum alloy layer 421 and the second edge of the tantalum-rich electrode portion 42 are both non-parallel to the perimeter of the substrate.

The above descriptions are only preferred embodiments of the present invention, and all changes and modifications made by the scope of the patent application of the present invention should be covered by the present invention.

40‧‧‧Back electrode

42‧‧‧Electrium-rich electrode

42a‧‧‧ wave contour

43‧‧‧Regional back surface electric field

100b‧‧‧ second surface

Around 101‧‧

421‧‧‧Aluminum-niobium alloy layer

422‧‧‧ first edge

423‧‧‧ second edge

Claims (16)

A solar cell comprising: a substrate having a first surface and a second surface; a front electrode disposed on the first surface; an aluminum-bismuth alloy layer, the aluminum-bismuth alloy layer being a ring An aluminum-bismuth alloy layer disposed on the second surface along an edge of the substrate; a passivation layer disposed on the second surface; and a back electrode on the passivation layer, the back electrode including a germanium-rich electrode The ytterbium-rich electrode portion is in contact with the aluminum-bismuth alloy layer through the passivation layer, wherein the aluminum-niobium alloy layer and/or the ytterbium-rich electrode portion has a first edge and a second edge, and The second edge is between the first edge and a perimeter of the substrate, wherein at least a portion of the second edge is non-parallel to a perimeter of the substrate. The solar cell of claim 1, wherein the second edge has a convex contour. The solar cell of claim 2, wherein the convex contour is a wave profile. The solar cell of claim 2, wherein the convex contour is a zigzag profile. The solar cell of claim 2, wherein the convex contour is a city-like profile. The solar cell of claim 2, wherein the convex contour is a hollow grid-like profile. The solar cell of claim 2, wherein the convex contour is a continuous hollow grid-like profile. The solar cell of claim 2, wherein the convex contour is a hollow pyramid-shaped profile. The solar cell of claim 1, wherein the passivation layer comprises aluminum oxide. The solar cell of claim 1, wherein the two opposite first edges further comprise at least one back surface electric field. The solar cell of claim 10, wherein the back electrode between the two opposite first edges further comprises at least one germanium-rich electrode portion, and the germanium-rich electrode portion passes through the The passivation layer is in electrical contact with the back surface. The solar cell of claim 1, wherein the first surface further comprises an N-type or P-type doped emitter layer, an oxide layer, and at least one layer of front anti-reflection coating. The solar cell of claim 1, wherein the back electrode comprises aluminum metal. The solar cell of claim 1, wherein the back surface electrode and the passivation layer further comprise a back protective layer. The solar cell of claim 10, wherein the back surface electrode and the passivation layer further comprise a back protective layer. The solar cell of claim 15, wherein the back electrode between the two opposite first edges further comprises at least one germanium-rich electrode portion, and the germanium-rich electrode portion passes through the A passivation layer and the backside protective layer are in electrical contact with the back surface.