CN108615775B - An interdigitated back-contact heterojunction monocrystalline silicon cell - Google Patents

Abstract

The invention discloses an interdigital back contact heterojunction monocrystalline silicon battery, which comprises: an N-type monocrystalline silicon substrate having a front surface and a back surface opposite to each other; doped N arranged on the front surface of N-type monocrystalline silicon substrate ⁺ A layer and a front side N-type amorphous silicon layer; the P-type amorphous silicon layer and the back N-type amorphous silicon layer are arranged on the back of the N-type monocrystalline silicon substrate at intervals. The interdigital back contact heterojunction monocrystalline silicon battery provided by the invention has the advantages that the thickness of the front N-type amorphous silicon layer of the conventional back contact heterojunction N-type monocrystalline silicon battery is reduced, and the lightly doped N is arranged below the amorphous silicon-oxygen alloy layer ⁺ The layer can reduce light absorption and light loss of the N-type amorphous silicon layer and can utilize N ⁺ The layer realizes a partial field passivation function, so that the photoelectric conversion efficiency of the battery is improved; at the same time N ⁺ The layers can also provide lateral low resistance conductive paths for photo-generated carriers, thereby reducing series resistance losses and improving the short circuit current, fill factor and conversion efficiency of the cell.

Description

An interdigitated back-contact heterojunction monocrystalline silicon cell

Technical field

The present invention relates to the technical field of solar cells, and in particular, to an interdigitated back contact heterojunction monocrystalline silicon cell.

Background technique

Crystalline silicon solar cells have the characteristics of high conversion efficiency, good working stability, long working life and mature manufacturing technology. They are the main force in the current solar photovoltaic market. Compared with boron-doped P-type monocrystalline silicon materials, phosphorus-doped N-type monocrystalline silicon materials have extremely low boron content, and the light-induced attenuation caused by boron-oxygen pairs can be ignored. Some metal impurities in N-type silicon materials have a negative impact on minority carrier vacancies. The trapping ability of holes is lower than the trapping ability of impurities in P-type materials for minority carrier electrons. N-type silicon has a higher minority carrier lifetime than P-type silicon at the same doping concentration. These characteristics give N-type silicon cells the potential advantages of long life and high efficiency. N-type silicon solar cells have become the development direction of high-efficiency crystalline silicon solar cells in the future.

An Interdigitated Back Contact (IBC) cell based on an N-type monocrystalline silicon substrate has no electrode distribution on the front. The emitter and base are arranged crosswise on the back of the cell to collect the photogenerated carrier generated by the photovoltaic effect of crystalline silicon respectively. Because there is no optical loss caused by the metal electrode grid on the front of the battery, it can effectively increase the short-circuit current of the battery and improve the conversion efficiency. Amorphous silicon (a-Si:H)/N-type monocrystalline silicon (c-Si) heterojunction (Hetero-junction with Intrinsic Thin-layer, HIT) battery relies on intrinsic amorphous silicon (i-a-Si:H) Good surface passivation effect. By inserting an extremely thin layer of intrinsic amorphous silicon between P-type amorphous silicon or N-type amorphous silicon and the single-crystal silicon substrate, defects on the surface of single-crystal silicon can be passivated and significantly improved. Reduce the recombination of the interface state and the surface of single crystal silicon, thereby improving the minority carrier lifetime and obtaining a higher open circuit voltage.

N-type silicon back-contact heterojunction solar cell (hereinafter referred to as: HIBC cell) is a coupling cell of heterojunction cell and interdigital back-contact cell. It utilizes the superior surface passivation performance of amorphous silicon and combines the IBC structure with no metal on the front. The structural advantage of the shading is compatible with the excellent characteristics of the two batteries, with good optical and electrical properties, low process temperature, and good stability; there is no grid line shading on the front of the battery, ensuring that the battery has a high short-circuit current (Isc); the battery There are high-quality hydrogenated amorphous silicon passivation layers on both front and back sides, ensuring that the battery has a high open circuit voltage (Voc).

Usually, the front side of the interdigitated back-contact heterojunction N-type monocrystalline silicon cell adopts a structure in which N-type monocrystalline silicon matrix, intrinsic amorphous silicon, N-type amorphous silicon, and anti-reflection layers are sequentially stacked from the inside to the outside. The advantage of the structure is that intrinsic amorphous silicon provides excellent chemical passivation performance, and N-type amorphous silicon achieves field passivation; the disadvantage is that the front-side photogenerated carrier generation rate is high, while the amorphous silicon layer absorbs light and generates photogenerated carriers. The carrier lifetime is very short and it is difficult to form an effective photocurrent, thereby reducing the short-circuit current density, causing a decrease in the short-wave effect and an increase in optical losses; furthermore, in order to reduce the short-circuit current density of the battery caused by the light absorption of the amorphous silicon layer decline, when designing and manufacturing back-contact heterojunction N-type monocrystalline silicon cells, it is necessary to optimize and control the thickness of the N-type amorphous silicon and intrinsic amorphous silicon layers on the front of the cell, while achieving excellent passivation performance and further improving the cell conversion efficiency brings difficulties.

Contents of the invention

In order to solve the above-mentioned problems in the prior art, the present invention provides an interdigital back contact heterojunction monocrystalline silicon cell to reduce the light loss on the front of the cell in the prior art and improve the photoelectric conversion efficiency of the cell.

In order to achieve the above-mentioned object of the invention, the present invention adopts the following technical solutions:

The invention provides an interdigital back contact heterojunction single crystal silicon battery, including:

An N-type single crystal silicon substrate, the N-type single crystal silicon substrate has an opposite front and a back;

A doped N ⁺ layer and a front N-type amorphous silicon layer provided on the front side of the N-type single crystal silicon substrate;

A P-type amorphous silicon layer and a back-side N-type amorphous silicon layer are provided on the back side of the N-type single crystal silicon substrate.

Preferably, the doped N ⁺ layer is a lightly doped N ⁺ layer, the surface doping concentration of the doped N ⁺ layer is less than 1×10 ¹⁸ cm ^-3 , and the diffusion depth is 0.2 to 1 μm.

Preferably, the thickness of the front N-type amorphous silicon layer is 1 to 10 nm.

Preferably, the single crystal silicon cell further includes an amorphous silicon oxygen alloy front passivation layer disposed between the doped N ⁺ layer and the front N-type amorphous silicon layer.

Preferably, the thickness of the amorphous silicon-oxygen alloy front passivation layer is 1 to 10 nm, and its optical energy gap is greater than 2 eV.

Preferably, the monocrystalline silicon cell further includes an anti-reflection layer provided on the surface of the front N-type amorphous silicon layer.

Preferably, the anti-reflection layer is one or a combination of oxide and nitride, and the thickness of the anti-reflection layer is 50 to 200 nm.

Preferably, the monocrystalline silicon cell further includes a contact layer provided on the P-type amorphous silicon layer and the back N-type amorphous silicon layer, and a contact layer provided on the P-type amorphous silicon layer and the back N-type amorphous silicon layer. Insulating spacer layer (10) between silicon layers.

Preferably, the contact layer is composed of a transparent conductive film and a stack of metal electrodes. The transparent conductive film includes tin-doped In ₂ O ₃ and aluminum-doped ZnO. The metal electrode is silver, copper or aluminum.

Preferably, the monocrystalline silicon cell further includes an amorphous silicon-oxygen alloy back passivation layer provided on the back of the N-type monocrystalline silicon substrate.

Compared with the prior art, the interdigitated back-contact heterojunction monocrystalline silicon cell of the present invention thins the thickness of the N-type amorphous silicon layer on the front of the conventional back-contact heterojunction N-type monocrystalline silicon cell, and makes the A lightly doped N ⁺ layer is placed under the silicon-oxygen alloy layer, which can not only reduce the light absorption and light loss of the N-type amorphous silicon layer, but also use the N ⁺ layer to achieve partial field passivation function, improving the photoelectric conversion efficiency of the battery. ; At the same time, the N ⁺ layer can also provide a lateral low-resistance conductive channel for photogenerated carriers, thereby reducing series resistance losses and improving the short-circuit current, fill factor and conversion efficiency of the battery.

In addition, an amorphous silicon-oxygen alloy with a wider optical energy gap is used on the front of the battery instead of the intrinsic amorphous silicon layer as the passivation layer. On the one hand, it can reduce the absorption of the passivation layer in the blue light region, reduce light loss, and improve the performance of the battery. The short-circuit current density, on the other hand, the surface defect density of amorphous silicon-oxygen alloy is lower than that of intrinsic amorphous silicon, which can achieve better interface passivation effect.

Description of the drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings needed to be used in the description of the embodiments or prior art will be briefly introduced below. Obviously, the drawings in the following description are only illustrative of the present invention. For some embodiments, for those of ordinary skill in the art, other drawings can be obtained based on these drawings without exerting creative efforts.

Figure 1 is a schematic structural diagram of an interdigitated back contact heterojunction monocrystalline silicon cell according to an embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some examples of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without any creative work fall within the protection scope of the present invention.

Referring to Figure 1, an interdigital back contact heterojunction monocrystalline silicon cell according to an embodiment of the present invention is shown. The monocrystalline silicon cell includes an N-type monocrystalline silicon substrate 1, wherein the N-type monocrystalline silicon substrate 1 has Opposite one front and one back; on the front of the N-type single crystal silicon substrate 1, a single-sided lightly doped N ⁺ layer 2, an amorphous silicon oxygen alloy (a-SiOx:H) front passivation layer 3, and a front N+ layer are sequentially prepared Type amorphous silicon layer 4 and anti-reflection layer 5; prepare an amorphous silicon oxygen alloy (a-SiOx:H) amorphous silicon oxygen alloy back passivation layer 6 on the back of the N-type single crystal silicon substrate 1; on the amorphous silicon A P-type amorphous silicon layer 7 and a back N-type amorphous silicon layer 8 are alternately deposited on the surface of the oxygen alloy back passivation layer 6; transparent layers are sequentially deposited on the surfaces of the P-type amorphous silicon layer 7 and the back N-type amorphous silicon layer 8 respectively. The conductive film and the metal film form the contact layer 9; an insulating isolation layer 10 is deposited in the area between the P-type amorphous silicon layer 7 and the back N-type amorphous silicon layer 8.

By thinning the thickness of the N-type amorphous silicon layer 4 on the front side of the back-contact heterojunction N-type monocrystalline silicon cell and setting up a lightly doped N ⁺ layer under the amorphous silicon-oxygen alloy layer, the N-type non-crystalline silicon layer can be reduced. Due to the light absorption and light loss of the crystalline silicon layer 4, the lightly doped N ⁺ layer can be used to achieve partial field passivation function. At the same time, the lightly doped N ⁺ layer can also provide a lateral low-resistance conductive channel for photogenerated carriers. Thereby reducing the series resistance loss, improving the filling factor and conversion efficiency of the battery, and improving the photoelectric conversion efficiency of the battery.

In addition to the above, since the unit area of back-contact heterojunction N-type monocrystalline silicon cells is often larger and the resistivity of the silicon substrate is higher, the photogenerated carriers generated on the front of the cell need to travel a longer distance to reach the back of the cell. being collected, the photogenerated carrier transport causes larger series resistance losses, resulting in a lower fill factor. The lightly doped N ⁺ layer 2 solves this problem very well. The lightly doped N ⁺ layer 2 can provide a lateral low-resistance conductive channel for photogenerated carriers, thereby reducing the series resistance loss and increasing the short-circuit current of the battery. Fill factor and conversion efficiency.

Preferably, the thickness of the front N-type amorphous silicon layer 4 is 1 to 10 nm, the doped N ⁺ layer 2 is a lightly doped N ⁺ layer, and the surface doping concentration of the doped N ⁺ layer 2 is less than 1×10 ¹⁸ cm ^-3 , diffusion depth is 0.2～1μm. The front N-type amorphous silicon layer 4 in this thickness range and the doped N ⁺ layer 2 with this doping degree and diffusion depth achieve both reduced light absorption and light loss of the N-type amorphous silicon layer and good passivation. The purpose of the effect.

Preferably, the thickness of the amorphous silicon-oxygen alloy front passivation layer 3 is 1 to 10 nm, and its optical energy gap is greater than 2 eV. The front side of the battery in this embodiment uses an amorphous silicon-oxygen alloy with a wider optical energy gap as the passivation layer instead of the intrinsic amorphous silicon layer. On the one hand, it can reduce the absorption of the passivation layer in the blue light region, reduce light loss, and improve The short-circuit current density of the battery, on the other hand, the surface defect density of amorphous silicon-oxygen alloy is lower than that of intrinsic amorphous silicon, which can achieve better interface passivation effect.

Similarly, the amorphous silicon-oxygen alloy back passivation layer 6 on the back of the N-type single crystal silicon substrate 1 uses an amorphous silicon-oxygen alloy with a wider optical band gap instead of the intrinsic amorphous silicon layer as the passivation layer. This setting To ensure the interface passivation effect of the interdigital back contact with the back of the heterojunction monocrystalline silicon cell, preferably, the thickness of the amorphous silicon-oxygen alloy back passivation layer 6 is 1 to 10 nm, and the optical energy gap is greater than 2 eV.

Preferably, the resistivity of the N-type single crystal silicon substrate 1 in this embodiment is 0.5-10Ω·cm, and the thickness is 100-300 μm;

The anti-reflection layer 5 is one or a combination of oxide and nitride, and the thickness of the anti-reflection layer 5 is 50 to 200 nm. The anti-reflection layer 5 of this thickness minimizes reflection loss and increases light transmittance, thereby improving the efficiency of the battery.

Referring to FIG. 1 , the thickness of the P-type amorphous silicon layer 7 is 10 to 100 nm, and the width is 100 to 1000 μm. The thickness of the backside N-type amorphous silicon layer 8 is the same as the thickness of the P-type amorphous silicon layer 7 , but its width is smaller than the width of the P-type amorphous silicon layer 7 .

Among them, the contact layer 9 may be composed of a transparent conductive film and a stack of metal electrodes. The transparent conductive film includes tin-doped In ₂ O ₃ and aluminum-doped ZnO (AZO), etc., and the metal electrode is made of silver, copper, aluminum or other materials. The width of the contact layer 9 is 10 to 300 μm.

Preferably, the insulating isolation layer 10 is made of one or a combination of silicon dioxide, silicon nitride, and aluminum oxide.

The interdigital back-contact heterojunction single-crystal silicon battery of the present invention thins the thickness of the N-type amorphous silicon layer on the front of the conventional back-contact heterojunction N-type single-crystal silicon battery, and sets a light weight under the amorphous silicon-oxygen alloy layer. The doped N ⁺ layer can not only reduce the light absorption and light loss of the N-type amorphous silicon layer, but also use the N ⁺ layer to achieve partial field passivation function, improving the photoelectric conversion efficiency of the battery; at the same time, the N ⁺ layer can also Provides a lateral low-resistance conductive channel for photogenerated carriers, thereby reducing series resistance losses and improving the short-circuit current, fill factor and conversion efficiency of the battery.

In addition, an amorphous silicon-oxygen alloy with a wider optical energy gap is used on the front of the battery instead of the intrinsic amorphous silicon layer as the passivation layer. On the one hand, it can reduce the absorption of the passivation layer in the blue light region, reduce light loss, and improve the performance of the battery. The short-circuit current density, on the other hand, the surface defect density of amorphous silicon-oxygen alloy is lower than that of intrinsic amorphous silicon, which can achieve better interface passivation effect.

While the invention has been shown and described with reference to specific embodiments, it will be understood by those skilled in the art that modifications may be made in form and form without departing from the spirit and scope of the invention as defined by the appended claims and their equivalents. Various changes in details.

Claims (8)

1. An interdigital back contact heterojunction single crystal silicon cell, comprising:

an N-type monocrystalline silicon substrate (1), said N-type monocrystalline silicon substrate (1) having opposite front and back sides;

the doped N is arranged on the front surface of the N-type monocrystalline silicon substrate (1) ⁺ A layer (2) and a front N-type amorphous silicon layer (4), wherein the thickness of the front N-type amorphous silicon layer (4) is 1nm, and the doped N ⁺ Layer (2) is lightly doped N ⁺ A layer doped with N ⁺ The surface doping concentration of the layer (2) is less than 1×10 ¹⁸ cm ^-3 The diffusion depth is 0.2-1 mu m;

and the P-type amorphous silicon layer (7) and the back N-type amorphous silicon layer (8) are arranged on the back of the N-type monocrystalline silicon substrate (1) at intervals.

2. The single crystal silicon cell of claim 1 further comprising a dopant N disposed in the single crystal silicon cell ⁺ And an amorphous silicon oxygen alloy front passivation layer (3) between the layer (2) and the front N-type amorphous silicon layer (4).

3. Single crystal silicon cell according to claim 2, characterized in that the thickness of the amorphous silicon oxide pre-passivation layer (3) is 1-10 nm, the optical energy gap of which is greater than 2eV.

4. A single crystal silicon cell according to claim 3, further comprising an anti-reflection layer (5) provided on the surface of the front-side N-type amorphous silicon layer (4).

5. The single crystal silicon cell according to claim 4, wherein the anti-reflection layer (5) is one or a combination of two of oxide and nitride, and the thickness of the anti-reflection layer (5) is 50-200 nm.

6. A single crystal silicon cell according to claim 3, further comprising a contact layer (9) provided on the P-type amorphous silicon layer (7) and the back-side N-type amorphous silicon layer (8) and an insulating isolation layer (10) provided between the P-type amorphous silicon layer (7) and the back-side N-type amorphous silicon layer (8).

7. Single crystal silicon cell according to claim 6, characterized In that the contact layer (9) consists of a stack of a transparent conductive film comprising tin doped In and a metal electrode ₂ O ₃ And aluminum doped ZnO, wherein the metal electrode is silver, copper or aluminum.

8. The monocrystalline silicon cell according to claim 7, further comprising an amorphous silicon oxygen alloy back passivation layer (6) provided on the back side of the N-type monocrystalline silicon substrate (1).