KR20180076433A - Bifacial tandem solar cell and method of manufacturing the same - Google Patents

Abstract

Disclosed is a bifacial tandem photovoltaic cell capable of improving a short circuit current. The bifacial tandem photovoltaic cell comprises: a heterojunction photovoltaic cell unit; a thin film photovoltaic cell unit; a buffer layer disposed between the heterojunction photovoltaic cell unit and the thin film photovoltaic cell unit; a complex function layer formed on a lower surface of the heterojunction photovoltaic cell unit and having a microcrystalline hydrogenated silicon oxide (n-type μc-SiOx:H or nc-SiOx:H) thin film formed by injecting carbon dioxide (CO_2); and first and second electrodes respectively formed on an upper surface of the thin film photovoltaic cell unit and a lower surface of the complex function layer.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a double-side light receiving type tandem solar cell,

The present invention relates to a double-sided light receiving type tandem solar cell capable of generating electric energy using sunlight incident through an upper surface and a lower surface, and a method of manufacturing the same.

Researches on silicon based tandem solar cells have been actively carried out for the production of high efficiency solar cells.

A tandem solar cell has a structure that effectively utilizes solar light having a wide wavelength range by stacking two or more layers having different optical band gaps. In recent years, in order to maximize the photoelectric conversion efficiency of such a tandem type solar cell, research is being conducted on a structure in which sunlight is incident on both sides, not just one side.

However, in the tandem type solar cell in which the upper cell and the lower cell are bonded as described above, the total open-circuit voltage has a high value as a sum of the open-circuit voltage of the upper cell and the open- The short-circuit current of the tandem-type solar cell is matched with a small value of the short-circuit current of the cell. Therefore, a technique for improving the short-circuit current of the tandem-type solar cell is desperately required.

An object of the present invention is to provide a double-sided light receiving type tandem solar cell capable of improving a short circuit current by forming a buffer layer between a heterojunction solar cell unit and a thin film solar cell unit and forming a multi- Battery.

A double-sided light receiving type tandem solar cell according to an embodiment of the present invention includes a heterojunction solar cell unit; A thin film solar cell unit disposed above the heterojunction solar cell unit; A buffer layer disposed between the heterojunction solar cell unit and the thin film solar cell unit to form a tunnel recombination junction therebetween; (Microcrystalline hydrogenated silicon oxide (n-type μc-SiOx: H or nc-SiOx: H) thin film formed on the lower surface of the heterojunction solar cell unit and formed by injecting a carbon dioxide layer; A first electrode formed on an upper surface of the thin film solar cell unit; And a second electrode formed on the lower surface of the multi-functional layer.

In one embodiment, the buffer layer may include a p-type microcrystalline hydrogenated silicon (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H) thin film.

According to the double-side light receiving type tandem solar cell according to the embodiment of the present invention, a p-type microcrystalline hydrogenated silicon (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H) thin film, it is possible to improve the junction characteristics of the heterojunction solar cell unit and the thin film solar cell unit. The microcrystalline hydrogenated silicon oxide (n-type μc-SiOx: H), which is formed by injecting carbon dioxide (CO 2) gas having a refractive index of about 2.0, can maintain high conductivity while having a high- Or nc-SiOx: H) thin film to arrange a multi-functional layer that serves as a dual role of electric conduction and light reflection, thereby improving the short-circuit current.

1 is a cross-sectional view illustrating a double-side light receiving type tandem solar cell according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a structure of a double-side light receiving type tandem solar cell ('Tandem cell (1) -No buffer layer') without a buffer layer and a buffer layer formed of a p-type microcrystalline hydrogenated silicon (nc-Si: Example 2 having a buffer layer formed of a thin film of double-side light receiving type tandem solar cell ('Tandem cell (2) -With buffer layer') and p-type microcrystalline hydrogenated silicon oxide (nc-SiOx: H) Current relationship for a light-receiving type tandem solar cell ("Tandem cell (3) -With buffer layer").
3 is a schematic diagram of a double-side light-receiving type light-emitting device according to Example 1 having a buffer layer formed of a double-side light receiving type tandem solar cell ('No buffer layer') and a p-type microcrystalline hydrogenated silicon (nc-Si: H) Type buffer layer formed of a tandem solar cell ('With buffer layer (1)') and a p-type microcrystalline hydrogenated silicon oxide (nc-SiOx: H) (FF) and open-circuit voltage (Voc) of the layer (2) '.

Hereinafter, embodiments of the present invention will be described in detail. The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It is to be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but on the contrary, is intended to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures are enlarged to illustrate the present invention in order to clarify the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the term "comprises" or "having ", etc. is intended to specify that there is a feature, step, operation, element, part or combination thereof described in the specification, , &Quot; an ", " an ", " an "

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not.

1 is a perspective view illustrating a double-side light receiving type tandem solar cell according to an embodiment of the present invention.

Referring to FIG. 1, a double-sided light receiving type tandem solar cell 100 according to an embodiment of the present invention includes a heterojunction solar cell unit 110, a thin film solar cell unit 120, a buffer layer 130, A first electrode 150, and a second electrode 160. The first electrode 150 and the second electrode 160 are formed on the first electrode 150 and the second electrode 160, respectively.

The heterojunction solar cell unit 110 may include a silicon substrate 111, an emitter layer 112, a rear front layer 113, a first passivation layer 114, and a second passivation layer 115.

The silicon substrate 111 may include a first conductive type crystalline silicon substrate. For example, the silicon substrate 111 may be an n-type crystalline silicon substrate.

The emitter layer 112 may be formed on the upper surface of the silicon substrate 111 and may be formed of a second conductive type semiconductor material opposite to the silicon substrate 111, Junctions can be formed. In one embodiment, when the silicon substrate 111 is an n-type crystalline silicon substrate, the emitter layer 112 may be formed of a p-type semiconductor material. For example, the emitter layer 112 is a p- type impurity boron (B) doped amorphous hydrogenated silicon: hydrogenated amorphous silicon oxide formed by injecting (a Si-H) thin film, a carbon dioxide (CO ₂₎ gas ( (a-SiC: H) thin film formed by implanting an a-Si _x : H thin film or a methane (CH ₄ ) gas into the amorphous hydrogenated silicon carbide thin film. The emitter layer 112 may be formed to a thickness of about 5 to 10 nm. When the thickness of the emitter layer 112 is less than 5 nm, the reproducibility and uniformity of the thin film may be deteriorated. When the thickness of the emitter layer 112 is more than 10 nm, the light absorption amount of the emitter layer 112 is excessively increased Lt; / RTI >

The rear front layer 113 is disposed on the lower surface of the silicon substrate 111 and may be formed of the same first conductive type semiconductor material as the silicon substrate 111 and may form a rear electric field. In one embodiment, when the silicon substrate 111 is an n-type crystalline silicon substrate, the rear front layer 113 may be formed of an n-type semiconductor material. For example, the rear front layer 113 may be formed of an amorphous hydrogenated silicon (a-Si: H) thin film doped with phosphorus (P) which is an n-type impurity or a microcrystalline hydrogenated silicon (μc- : H) thin film. The rear front layer 113 may be formed to a thickness of about 7 to 10 nm.

The first passivation layer 114 and the second passivation layer 115 are formed between the silicon substrate 111 and the emitter layer 112 and between the silicon substrate 111 and the rear front layer 113, . The first and second passivation layers 114 and 115 may be formed of an intrinsic semiconductor material. For example, the first and second passivation layers 114 and 115 may comprise an intrinsic amorphous hydrogenated silicon (a-Si: H) thin film. The first and second passivation layers 114 and 115 may be formed to a thickness of about 3 to 5 nm.

The thin film solar cell unit 120 may be disposed on the upper portion of the heterojunction solar cell unit 110, that is, on the emitter layer, and the light absorbing layer 121, the first semiconductor layer 122, And a semiconductor layer 123.

The light absorption layer 121 may be formed of an intrinsic semiconductor material having a higher band gap than the emitter layer 112 and located on the emitter layer 112 of the heterojunction solar cell unit 110. For example, the light absorption layer 121 is formed of intrinsic amorphous silicon hydride (a-Si: H) or germanium doped amorphous silicon hydride (a-SiGe: H) having a bandgap larger than that of the emitter layer 112 . The light absorption layer 121 may be formed to a thickness of about 400 to 600 nm.

The first semiconductor layer 122 may be located between the light absorption layer 121 and the emitter layer 112 of the heterojunction solar cell unit 110 and may be formed of an n-type semiconductor material. For example, the first semiconductor layer 122 may be an amorphous hydrogenated silicon (a-Si: H) thin film doped with phosphorus (P) which is an n-type impurity or a microcrystalline hydrogenated silicon (μc- Si: H) thin film. The first semiconductor layer 122 may be doped with an n-type impurity at a high concentration for the lower electric field formation and the tunnel recombination bonding.

The second semiconductor layer 123 may be formed of a p-type semiconductor material which is located on the light absorption layer 121 and is opposite to the first semiconductor layer 122. For example, the second semiconductor layer 123 may include a p-type amorphous silicon thin film, an amorphous hydrogenated silicon thin film doped with boron (B) which is a p-type impurity, an amorphous hydrogenated silicon oxide formed by implanting carbon dioxide (a-SiOx: H) thin film, amorphous hydrogenated silicon carbide (p-type a-SiC: H) thin film formed by injecting methane (CH4) gas, p- type microcrystalline hydrogenated silicon Si: H) thin film or a p-type microcrystalline hydrogenated silicon oxide (μc-SiOx: H or nc-SiOx: H) thin film. The second semiconductor layer 123 may be formed to a thickness of about 20 to 30 nm.

The buffer layer 130 may be disposed between the heterojunction solar cell unit 110 and the thin film solar cell unit 120. The buffer layer 130 is disposed between the emitter layer 112 of the heterojunction solar cell unit 110 and the second semiconductor layer 123 of the thin film solar cell unit 120 to form a tunnel junction recombination junctions. The buffer layer 130 may include a p-type microcrystalline hydrogenated silicon (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H) thin film and may have high conduction characteristics. The buffer layer 130 facilitates the tunnel recombination junction to improve the filling ratio of the double-side light receiving type tandem solar cell 100 according to the present invention.

The multifunction functional layer 140 may be disposed below the heterojunction solar cell unit 110. The multi-functional layer 140 may have a high bandgap and maintain a high conductivity, and may be formed of a material having a refractive index of about 2.0. For example, the multi-functional layer 140 may include an n-type microcrystalline hydrogenated silicon oxide (Hc) or nc-SiOx (H) thin film formed by injecting a carbon dioxide gas. The buffer layer 140 may serve as a dual function of electrical conduction and light reflection, thereby significantly improving the short-circuit current of the double-side light receiving type tandem solar cell 100 according to the present invention.

The first electrode 150 may be formed on the thin film solar cell unit 120 and the second electrode 160 may be formed below the buffer layer 140. The first electrode 150 may include a transparent conductive oxide thin film 151 and an upper grid pattern 152 formed on the transparent conductive oxide thin film 151. The second electrode 160 may include a lower grid pattern. The upper grid pattern and the lower grid pattern may be formed of aluminum or silver.

FIG. 2 is a schematic view showing a structure of a double-side light receiving type tandem solar cell ('Tandem cell (1) -No buffer layer') without a buffer layer and a buffer layer formed of a p-type microcrystalline hydrogenated silicon (nc-Si: Example 2 having a buffer layer formed of a thin film of double-side light receiving type tandem solar cell ('Tandem cell (2) -With buffer layer') and p-type microcrystalline hydrogenated silicon oxide (nc-SiOx: H) FIG. 3 is a graph showing a voltage-current relationship of a tandem photodiode ('Tandem cell (3) -With buffer layer') of a light receiving type. ('With buffer layer (1)') of Example 1 and a p-type microcrystalline silicon (nc-Si: H) The double-sided light-receiving type tandem of Example 2 having a buffer layer formed of a thin film of hydrogenated silicon oxide (nc-SiOx: H) Amount of the battery charged ( 'With buffer layer (2)') is the result of measuring the rate (FF) and the open-circuit voltage (Voc).

Referring to FIGS. 2 and 3, a p-type microcrystalline silicon hydride (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H ) Thin film is formed, the open voltage Voc is increased and the current density is increased according to the voltage, and the filling factor (FF) is improved.

Hereinafter, a method of manufacturing the double-side light receiving type tandem solar cell 100 according to the embodiment of the present invention will be described in detail.

In order to manufacture the double-sided light receiving type tandem solar cell 100 according to the embodiment of the present invention, first and second passivation layers are formed on the upper and lower surfaces of the RCA-cleaned n-type silicon wafer substrate .

The first and second passivation layers may be formed by depositing an intrinsic amorphous silicon hydride (a-Si: H) thin film on the upper and lower surfaces of the silicon wafer substrate. Each of the first and second passivation layers may be formed to a thickness of about 3 to 5 nm.

Next, an emitter layer and a rear whole layer may be formed on the first passivation layer and the second passivation layer, respectively.

The emitter layer may include an amorphous hydrogenated silicon (a-Si: H) thin film doped with boron (B) which is a p-type impurity, an amorphous hydrogenated silicon oxide formed by implanting carbon dioxide (CO ₂ ) (a-SiC: H) thin film formed by implanting an a-Si _x : H thin film or a methane (CH ₄ ) gas into the amorphous hydrogenated silicon carbide thin film. The emitter layer may be formed to a thickness of about 5 to 10 nm.

The rear whole layer is formed by depositing an amorphous hydrogenated silicon (a-Si: H) thin film doped with phosphorus (P) which is an n-type impurity or a microcrystalline hydrogenated silicon (μc-Si: H or nc-Si : ≪ / RTI > H) thin film. The backside front layer may be formed to a thickness of about 7 to 10 nm.

Subsequently, a multi-functional layer may be formed on the rear whole layer.

The multi-functional layer may be formed by depositing an n-type microcrystalline hydrogenated silicon oxide film (n-type μc-SiOx: H or nc-SiOx: H) into which carbon dioxide .

Subsequently, a buffer layer may be formed on the emitter layer.

The buffer layer may be formed by depositing a p-type microcrystalline silicon hydride (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H) thin film having relatively high conduction characteristics on the emitter layer.

Then, the first semiconductor layer, the light absorbing layer, and the second semiconductor layer may be sequentially formed on the buffer layer.

The first semiconductor layer is formed on the buffer layer by depositing a p-type amorphous silicon thin film, an amorphous hydrogenated silicon thin film doped with boron (B) as a p-type impurity, an amorphous hydrogenated silicon oxide (a- SiC: H or nc-Si: H) thin film, a p-type a-SiC: H thin film formed by injecting methane (CH4) gas, a p-type microcrystalline hydrogenated silicon ) Thin film or a p-type microcrystalline hydrogenated silicon oxide (μc-SiOx: H or nc-SiOx: H) thin film. The first semiconductor layer may be formed to a thickness of about 20 to 30 nm.

The light absorption layer may include an a-Si: H thin film or a germanium-doped amorphous silicon hydride (a-SiGe: H) thin film having a bandgap larger than that of the emitter layer 112 on the first semiconductor layer. As shown in FIG. The light absorption layer may be formed to a thickness of about 400 to 600 nm.

The second semiconductor layer is formed on the light absorption layer by using an amorphous hydrogenated silicon (a-Si: H) thin film or microcrystalline hydrogenated silicon (μc-Si: H or nc- Si: H) thin film.

Then, a first electrode may be formed on the second semiconductor layer.

In order to form the first electrode, a transparent conductive oxide may be deposited on the first semiconductor layer, and then a first metal grid pattern may be formed thereon. The transparent conductive oxide may be formed to have a sheet resistance of about 10? / ?. The first metal grid pattern may be formed of aluminum or silver using a method such as evaporation, screen printing, or the like.

Next, a second electrode may be formed on the multi-functional layer.

The second electrode may be formed by forming a second metal grid pattern on the multi-functional layer by evaporation, screen printing, or the like. The second metal grid pattern may be formed of aluminum or silver.

According to the double-side light receiving type tandem solar cell according to the embodiment of the present invention, a p-type microcrystalline hydrogenated silicon (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H) thin film, it is possible to improve the junction characteristics of the heterojunction solar cell unit and the thin film solar cell unit. The microcrystalline hydrogenated silicon oxide (n-type μc-SiOx: H), which is formed by injecting carbon dioxide (CO 2) gas having a refractive index of about 2.0, can maintain high conductivity while having a high- Or nc-SiOx: H) thin film to arrange a multi-functional layer that serves as a dual role of electric conduction and light reflection, thereby improving the short-circuit current.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the present invention as defined by the following claims. It can be understood that it is possible.

100: double-side light receiving type tandem solar cell; 110: Heterojunction solar cell unit
111: silicon substrate 112: emitter layer
113: back surface layer 114: first passivation layer
115: second passivation layer 120: thin film solar cell unit
121: light absorbing layer 122: first semiconductor layer
123: second semiconductor layer 130: buffer layer
140: multi-function layer 150: first electrode
160: Second electrode

Claims (2)

A heterogeneous solar cell unit;
A thin film solar cell unit disposed above the heterojunction solar cell unit;
A buffer layer disposed between the heterojunction solar cell unit and the thin film solar cell unit to form a tunnel recombination junction therebetween;
(Microcrystalline hydrogenated silicon oxide (n-type μc-SiOx: H or nc-SiOx: H) thin film formed on the lower surface of the heterojunction solar cell unit and formed by injecting a carbon dioxide layer;
A first electrode formed on an upper surface of the thin film solar cell unit; And
And a second electrode formed on a lower surface of the multifunction functional layer. The method according to claim 1,
Wherein the buffer layer comprises a p-type microcrystalline hydrogenated silicon (nc-Si: H) thin film or a hydrogenated silicon oxide (nc-SiOx: H) thin film.

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