TW201338179A - Back-contact solar cells - Google Patents

Abstract

A back-contact solar cell comprises a substrate having a first surface and a second side opposite to each other, at least one first conductive type doped region disposed on the second surface, at least one second conductive type doped region disposed beside the first conductive type doped region, at least one second conductive type heavily doped region disposed between the first conductive type doped region and the second conductive type doped region, a first electrode connected to the first conductive type doped region, and a second electrode connecting to the second conductive type doped region. Disposing the second conductive type heavily doped region may reduce contact resistance, increase current density at the p-n junction to thereby improve the photoelectric conversion efficiency.

Description

Back contact solar cell

The present invention relates to a solar cell, and more particularly to a back contact solar cell in which a p-type electrode and an n-type electrode are disposed on the same side of the substrate.

Referring to FIG. 1, a known back contact solar cell 1 includes an n-type substrate 11, a semiconductor layer 12 on a front side 111 of the substrate 11, and a semiconductor layer 12 thereon. An anti-reflective layer 13 thereon, a p-type doping region 14 at a back surface 112 of the substrate 11, an n-type doping region 15 at the back surface 112, and a dielectric layer 16 on the back surface 112 And a p-type electrode 17 electrically connected to the p-type doping region 14, and an n-type electrode 18 electrically connected to the n-type doping region 15. The main feature of the back contact solar cell 1 is that the p-type electrode 17 and the n-type electrode 18 are both located on one side of the back surface 112 of the substrate 11. The front surface 111 of the battery 1 is not provided with an electrode, so that the light-receiving area can be avoided. Blocking, so you can increase the amount of light entering the front of the battery.

Of course, increasing the photocurrent density and conversion efficiency of the battery 1 is the focus of efforts of various manufacturers, and it is known that there is a pn junction between the p-doped region 14 and the n-doped region 15 of the battery 1. Higher current density, therefore, if further improvement can be made for the pn junction adjacent to each other, it is probable that a higher current density is obtained, so this case is developed for the structure of the battery 1 .

Accordingly, it is an object of the present invention to provide a back contact solar cell that can increase current density.

Therefore, the back contact solar cell of the present invention comprises: a substrate having a first surface and a second surface opposite to each other, at least one first conductive type doped region disposed at the second surface, at least one setting a second conductive type doped region located at the second surface and adjacent to the first conductive type doped region, at least one disposed at the second surface and located at the first conductive type doped region and the second a second conductive type heavily doped region between the conductive type doped regions, a first electrode connected to the first conductive type doped region, and a second electrode connected to the second conductive type doped region. The carrier concentration of the second conductivity type heavily doped region is greater than the carrier concentration of the second conductivity type doping region.

The effect of the present invention is that the second conductive type heavily doped region is disposed on one side of the second conductive type doped region, thereby reducing contact resistance and increasing current density at the pn junction, thereby improving photoelectric conversion effectiveness.

The above and other technical contents, features and advantages of the present invention will be apparent from the following detailed description of the preferred embodiments of the invention. Before the present invention is described in detail, it is noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 2, a first preferred embodiment of the back contact solar cell of the present invention comprises: a substrate 21, a first conductive type doped layer 22, an anti-reflective layer 23, and at least one first conductive type doped region. 24. At least one second conductive type doped region 25, at least one second conductive type heavily doped region 26, a dielectric layer 27, a first electrode 28, and a second electrode 29. The first conductivity type and the second conductivity type of the present embodiment are respectively n-type and p-type, but may be reversed in implementation.

The substrate 21 has a first surface 211 and a second surface 212 opposite to each other. The substrate 21 of the present embodiment is a first conductivity type substrate, specifically an n-type germanium substrate, and the first surface 211 is The light receiving surface, the second surface 212 is a back surface. The first face 211 can be made into a rough surface to increase the amount of light incident. The second surface 212 is stepped, and the purpose is to make the height position of the first conductive type doped region 24 and the second conductive type heavily doped region 26 located at the second surface 212 different between the two regions. The carriers are mutually diffused, so separating the two regions by different height regions is beneficial to the formation of the depletion region. However, the second surface 212 is not limited by a step shape, and may be, for example, a planar shape, as long as the first conductive type doping region 24 is spaced apart from the second conductive type heavily doped region 26.

The first conductive type doping layer 22 of the present embodiment is disposed on the first surface 211 of the substrate 21, which is an n-type semiconductor, and has a carrier concentration greater than the substrate 21, thereby forming a front electric field structure (Front-Side Field) , referred to as FSF), can improve the carrier collection rate and photoelectric conversion efficiency.

The anti-reflective layer 23 is located on the surface of the first conductive type doped layer 22, and is made of a material such as tantalum nitride (SiN _x ) for increasing the incident amount of light and reducing the surface recombination velocity (SRV). However, the present invention is not necessary to provide the anti-reflection layer 23.

The first conductive type doping region 24 of the present embodiment is disposed at the second surface 212 of the substrate 21, which is an n-type semiconductor and has a carrier concentration greater than that of the substrate 21.

The second conductive type doped region 25 of the present embodiment is a p-type semiconductor disposed at the second surface 212 of the substrate 21 and spaced apart from the first conductive type doped region 24, the second conductive type doped The height position of the impurity region 25 is different from the height position of the first conductive type doping region 24. However, as described above, the second surface 212 may also be a flat surface, and the height positions of the respective doped regions are the same.

The second conductive type heavily doped region 26 of the present embodiment is a p-type semiconductor disposed at the second surface 212 of the substrate 21 and located in the first conductive type doped region 24 and the second conductive type doped region. Between 25.

In this embodiment, the second conductive type doping region 25 may have a width of 2 mm to 20 μm and a carrier concentration of 1×10 ¹⁷ cm ⁻³ to 1×10 ²⁰ cm ⁻³ . The ratio of the width of the second conductive type doped region 25 to the width of the second conductive type heavily doped region 26 is greater than 2 and less than 100. The second conductive type heavily doped region 26 may have a carrier concentration of 1 × 10 ¹⁸ cm ^-3 to 5 × 10 ²⁰ cm ^-3 , and must be larger than the carrier concentration of the second conductive type doped region 25 because By forming the pn junction with the first conductivity type doped region 24 by the second conductivity type heavily doped region 26 having a higher carrier concentration, the current density at the pn junction can be effectively improved. However, if the existence region of the second conductive type heavily doped region 26 is too small and the width is too narrow, the current density cannot be effectively increased. Therefore, the width of the second conductive type doped region 25 and the second conductive portion are preferably The ratio of the width of the heavily doped region 26 is 4 to 10.

In the fabrication process, a p-type semiconductor region may be formed on the second surface 212 of the substrate 21 through a diffusion process, and then a second diffusion may be performed on a side portion of the p-type semiconductor region to form the second conductivity type. The heavily doped region 26, and the portion where the p-type semiconductor region is not subjected to the second diffusion, becomes the second conductive type doped region 25. The second conductive type heavily doped region 26 can be formed by using ion cloth values, laser doping, or screen printing, and printing a colloid containing a dopant to be doped, in addition to secondary diffusion. To reach.

The dielectric layer 27 is disposed on the second surface 212 of the substrate 21, and includes at least one pair of first vias 271 that should be doped with the first conductive type doping regions 24, and at least one pair of doped regions of the second conductive type doped regions 25 The second perforation 272. The material of the dielectric layer 27 may be an oxide, a nitride or a combination of the above materials. The dielectric layer 27 is used to fill and reduce defects on the surface or the substrate 21, thereby reducing the surface recombination rate of the carrier and improving the conversion of the battery. effectiveness.

The first electrode 28 is connected to the first conductive type doping region 24 via the first through hole 271, the first electrode 28 includes a first electrode portion 281 located in the first through hole 271, and a first electrode portion 281 is connected The portion 281 is located on the first protrusion 282 on the surface of the dielectric layer 27.

The second electrode 29 is connected to the second conductive type doped region 25 via the second through hole 272. The second electrode 29 includes a second electrode portion 291 located in the second through hole 272, and a second electrode connected to the second electrode The portion 291 is located on the second protrusion 292 on the surface of the dielectric layer 27.

It should be noted that, in fact, the first conductive type doped region 24, the second conductive type doped region 25, the second conductive type heavily doped region 26, the first through hole 271, the second through hole 272, and the first of the battery The number of the electrode portion 281, the first protrusion portion 282, the second electrode portion 291, and the second protrusion portion 292 are several, and the above-described structures are repeatedly arranged in the battery. However, the present embodiment is exemplified by one, but is not limited thereto. this. Moreover, when the number of the above-mentioned components is several, the first conductive type doped region 24 and the second conductive type doped region 25 are arranged at a staggered interval, and the opposite sides of each of the second conductive type doped regions 25 may be separately disposed. A second conductivity type heavily doped region 26.

In addition, the known types of back contact solar cells include: Interdigitated Back Contact (IBC) solar cells, Metal Wrap Through (MWT) solar cells, and emitter surrounds. An Emitter Wrap Through (EWT) solar cell. As shown in FIG. 3, in this embodiment, an IBC battery is taken as an example. The first electrode 28 and the second electrode 29 are in a finger-crossing pattern. However, the battery of the present invention may also be a MWT battery or an EWT battery, as long as The formation of partial heavy doping at the pn junction is the scope of protection of the present invention.

Referring to Annex 1, the measurement results of the current density (unit: A/cm ² ) of the battery of a comparative example and the battery of the present invention, the comparative example refers to the conventional battery of Fig. 1, and the present invention is compared with the comparative example. The higher carrier concentration is generated by heavy doping of the local region, so the current density at the pn junction is significantly increased.

In summary, the spirit of the present invention is that the second conductive type heavily doped region 26 is formed by partial heavy doping at the side portion of the second conductive type doped region 25, thereby reducing contact resistance. Increasing the current density at the pn junction to improve the photoelectric conversion efficiency is of great benefit to the application of the solar cell industry.

Referring to FIG. 4, a second preferred embodiment of the back contact solar cell of the present invention is substantially the same as the first preferred embodiment, except that the two opposite sides of the second conductive type doped region 25 of the present embodiment are opposite. A second conductivity type heavily doped region 26 is disposed on each side, wherein the second conductivity type heavily doped region 26 on the left side may be formed with another first conductivity type doped region (not shown) on the left side thereof. Pn junction. This embodiment can also increase the current density at the p-n junction, and its function will not be described again.

The above is only the preferred embodiment of the present invention, and the scope of the invention is not limited thereto, that is, the simple equivalent changes and modifications made by the scope of the invention and the description of the invention are All remain within the scope of the invention patent.

twenty one. . . Substrate

211. . . First side

212. . . Second side

twenty two. . . First conductive type doped layer

twenty three. . . Antireflection layer

twenty four. . . First conductivity type doping region

25. . . Second conductivity type doping region

26. . . Second conductivity type heavily doped region

27. . . Dielectric layer

271. . . First perforation

272. . . Second perforation

28. . . First electrode

281. . . First electrode portion

282. . . First protrusion

29. . . Second electrode

291. . . Second electrode portion

292. . . Second protrusion

Figure 1 is a schematic cross-sectional view of a known back contact solar cell;

2 is a cross-sectional view showing a first preferred embodiment of a back contact solar cell of the present invention;

3 is a rear view of a battery, mainly showing that the first preferred embodiment may be an interdigitated back contact solar cell;

4 is a cross-sectional view showing a second preferred embodiment of a back contact solar cell of the present invention.

【annex】

(a) of Annex 1 is a current density distribution diagram at the p-n junction of the battery of a comparative example; (b) of the attachment 1 is a current density distribution diagram at the p-n junction of the battery of the present invention.

twenty one. . . Substrate

211. . . First side

212. . . Second side

twenty two. . . First conductive type doped layer

twenty three. . . Antireflection layer

twenty four. . . First conductivity type doping region

25. . . Second conductivity type doping region

26. . . Second conductivity type heavily doped region

27. . . Dielectric layer

271. . . First perforation

272. . . Second perforation

28. . . First electrode

281. . . First electrode portion

282. . . First protrusion

29. . . Second electrode

291. . . Second electrode portion

292. . . Second protrusion

Claims (8)

A back contact solar cell comprising: a substrate having a first surface and a second surface opposite to each other; at least one first conductive type doped region disposed at the second surface; at least one second conductive type a doped region disposed at the second surface and located beside the first conductive type doped region; at least one second conductive type heavily doped region disposed at the second surface and located at the first conductive type doping Between the impurity region and the second conductivity type doping region, wherein a carrier concentration of the second conductivity type heavily doped region is greater than a carrier concentration of the second conductivity type doping region; a first electrode connecting the first a conductive type doped region; and a second electrode connected to the second conductive type doped region. The back contact solar cell according to claim 1, wherein the second conductive type heavily doped region is disposed on each of opposite sides of the second conductive type doped region. The back contact solar cell of claim 1, wherein a ratio of a width of the second conductive type doped region to a width of the second conductive type heavily doped region is greater than 2 and less than 100. The back contact solar cell according to any one of claims 1 to 3, wherein the second conductive type heavily doped region has a carrier concentration of 1 × 10 ¹⁸ cm ^-3 to 5 × 10 ²⁰ Cm ^-3 . The back contact solar cell of claim 1, wherein the second surface of the substrate is provided with a dielectric layer including at least one pair of first perforations that should be doped with the first conductivity type, and at least a pair of second vias corresponding to the second conductive type doping region, the first electrode is connected to the first conductive type doped region via the first through hole, and the second electrode is connected to the second conductive via the second through hole Type doped region. The back contact solar cell of claim 5, wherein the first electrode comprises at least one first electrode portion located in the first through hole, and the second electrode comprises at least one of the second through holes The second electrode portion. The back contact solar cell of claim 1, wherein the substrate is a substrate of a first conductivity type. The back contact solar cell of claim 1, wherein the back contact solar cell comprises an interdigitated back contact (IBC) solar cell, a metal surround-through (MWT) solar cell, or a shot Extremely surround-through (EWT) solar cells.