KR20150131576A - Solar cell - Google Patents

Abstract

According to an embodiment, a solar cell comprises: a support substrate; a rear electrode layer arranged on the support substrate; a light absorbing layer arranged on the rear electrode layer; a doping layer arranged on the light absorbing layer; a buffer layer arranged on the doping layer; and a front electrode layer arranged on the buffer layer. The doping layer comprises at least one element among Na, K, Se, and S.

Description

Solar cell {SOLAR CELL}

An embodiment relates to a solar cell.

Recently, as energy resources such as petroleum and coal are expected to be depleted, interest in alternative energy to replace them is increasing, and solar cells that produce electric energy from solar energy are attracting attention.

Solar cells (photovoltaic cells or solar cells) are the core elements of solar power generation that convert sunlight directly into electricity.

For example, if sunlight having an energy larger than band-gap energy of a semiconductor is incident on a solar cell made of a pn junction of semiconductors, an electron-hole pair is generated. The electron- (Photovoltage) occurs between pn as the electrons are collected into the n layer and the holes are collected into the p layer. At this time, when the load is connected to the electrodes at both ends, current flows.

Generally, a material containing an alkali substance can be doped to supply an alkali substance such as sodium into the light absorption layer of a solar cell.

At this time, NaF or KF or the like is used as a substance containing an alkali substance, and the fluorine (F) substance acts as an impurity on the surface of the light absorption layer.

Therefore, there is a demand for a solar cell having a new structure that can solve such a problem.

The embodiment attempts to provide a solar cell having improved light-to-electricity conversion efficiency.

A solar cell according to an embodiment includes: a support substrate; A rear electrode layer disposed on the supporting substrate; A light absorbing layer disposed on the rear electrode layer; A doping layer disposed on the light absorbing layer; A buffer layer disposed on the doped layer; And a front electrode layer disposed on the buffer layer, wherein the doping layer includes at least one element selected from the group consisting of sodium (Na), potassium (K), selenium (Se), and sulfur (S).

Solar cell according to the embodiment using at least one dopant material selected from the group consisting of _{Na 2 Se, K2 S e,} NaSe 2 O 3, K 2 SeO 3, Na 2 Se, K2 S e, NaSe 2 O 3 and K ₂ SeO ₃ So that the alkali material can be supplied into the light absorbing layer.

Accordingly, it is possible to remove the fluorine material remaining in the conventional NaF or KF or the like, thereby reducing the impurity content on the surface of the light absorption layer.

In addition, selenium of the doping material can compensate for the loss of selenium in the light absorbing layer that may occur during the process. In addition, by adjusting the band gap and the surface roughness by adjusting the concentration of sulfur and selenium, it is possible to reduce defects when depositing the buffer layer to be deposited later.

Therefore, the solar cell according to the embodiment can have overall improved efficiency and reliability.

1 is a plan view showing a solar cell according to an embodiment.
FIG. 2 is a cross-sectional view showing one end surface of a solar cell according to an embodiment.
3 is an enlarged cross-sectional view of portion A of Fig.
4 is another cross-sectional view showing an enlarged view of a portion A in Fig.
5 is a view showing a solar cell module to which a solar cell according to an embodiment is applied.

In the description of the embodiments, it is to be understood that each layer (film), area, pattern or structure may be referred to as being "on" or "under / under" Quot; includes all that is formed directly or through another layer. The criteria for top / bottom or bottom / bottom of each layer are described with reference to the drawings.

The thickness or the size of each layer (film), region, pattern or structure in the drawings may be modified for clarity and convenience of explanation, and thus does not entirely reflect the actual size.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 to 4, a solar cell according to an embodiment may include a supporting substrate 100, a rear electrode layer 2000, a light absorbing layer 300, a buffer layer 400, and a front electrode layer 500.

The supporting substrate 100 has a plate shape and can support the rear electrode layer 200, the light absorbing layer 300, the buffer layer 400, and the front electrode layer 500.

The support substrate 100 may be an insulator. The support substrate 100 may be a glass substrate, a plastic substrate, or a metal substrate. More specifically, the support substrate 100 may be a soda lime glass substrate. Alternatively, a ceramic substrate such as alumina, stainless steel, a flexible polymer, or the like may be used as the support substrate 100. The supporting substrate 100 may be transparent. The support substrate 100 may be rigid or flexible.

The back electrode layer 200 may be disposed on the supporting substrate 100. The rear electrode layer 200 may be a conductive layer. The rear electrode layer 200 may be formed of any one of molybdenum (Mo), gold (Au), aluminum (Al), chromium (Cr), tungsten (W), and copper (Cu). Of these, molybdenum has a smaller difference in thermal expansion coefficient than the support substrate 100 in comparison with other elements, so that it is possible to prevent peeling phenomenon from occurring due to its excellent adhesiveness.

In addition, the rear electrode layer 200 may include two or more layers. At this time, the respective layers may be formed of the same metal or may be formed of different metals.

The rear electrode layer 200 may have first through holes TH1 passing through the rear electrode layer 200. Referring to FIG. The first through holes (TH1) may be open regions that expose the upper surface of the support substrate (100). The first through grooves TH1 may have a shape extending in a first direction when viewed from a plane.

The width of the first through-holes TH1 may be about 80 占 퐉 to about 200 占 퐉.

The rear electrode layer 200 is divided into a plurality of rear electrodes by the first through holes TH1. That is, the rear electrodes can be defined by the first through holes TH1.

The rear electrodes may be spaced from each other by the first through holes TH1. The rear electrodes may be arranged in a stripe form.

Alternatively, the rear electrodes may be arranged in a matrix. At this time, the first through holes TH1 may be formed in a lattice form when viewed from a plane.

The light absorption layer 300 may be disposed on the rear electrode layer 200. In addition, the material contained in the light absorption layer 300 may be filled in the first through holes TH1.

The light absorption layer 300 may include an I-III-VI group compound. For example, the light absorbing layer 300 is copper-indium-gallium-selenide-based (Cu (In, Ga) Se _2; CIGS-based) crystal structure, a copper-indium-selenide-based or copper-gallium-selenide Crystal structure.

The energy band gap of the light absorption layer 300 may be about 1 eV to 1.8 eV.

Referring to FIG. 3, a doping layer 350 may be disposed on the light absorption layer. The doping layer 350 may supply the alkali material into the light absorbing layer 300. That is, the doping layer 350 may be doped with an alkali material into the light absorption layer 300.

The light absorbing layer and the back electrode layer are formed on the surface of the light absorbing layer and the doping layer inside the light absorbing layer by doping the alkaline substance such as sodium or potassium with the doping layer 350 on the light absorbing layer 300. [ The concentration of the alkali substance may be lowered as it extends in the surface direction.

In detail, the doping layer 350 can supply an alkali material such as sodium (Na) or potassium (K) into the light absorbing layer.

The doping layer 350 may include at least one element selected from the group consisting of sodium (Na), potassium (K), selenium (Se), and sulfur (S). Specifically, the doped layer 350 is of the _{Na 2 Se, K2 S e,} NaSe 2 O 3, K 2 SeO 3, Na 2 Se, K2 S e, NaSe 2 O 3 and K ₂ SeO _3, at least one compound .

The doping layer 350 may be formed on the light absorption layer 300 through an evaporation process. In detail, and at least one compound of the _{Na 2 Se, K2 S e,} NaSe 2 O 3, K 2 SeO 3, Na 2 Se, K2 S e, NaSe 2 O 3 and K ₂ SeO ₃ formed through the deposition process, Oxygen residues such as SO3 or SeO3 can be removed through a water washing process.

The doping layer 350 may be formed to a thickness of about 20 nm to about 40 nm. When the thickness of the doping layer 350 is less than about 20 nm, a sufficient amount of the doping material may not be supplied into the light absorbing layer 300. If the thickness of the doping layer 350 is about 40 nm The process efficiency may be lowered.

The doping layer 350 may be disposed in a plurality of layers. In detail, the doping layer 350 may include at least two layers.

For example, as shown in FIG. 4, the doping layer 350 may include a first doping layer 351 and a second doping layer 352. In detail, the doping layer 350 may include a first doping layer 351 disposed on the light absorbing layer 300 and a second doping layer 352 disposed on the first doping layer 351 have.

The first doping layer 351 and the second doping layer 352 may include the same or different materials. In detail, the first doped layer 351 and the second doped layer 352 is a Na ₂ Se, K2 _S e, NaSe ₂ O _3, K ₂ SeO _3, Na ₂ Se, K2 _S e, NaSe ₂ O ₃ and it may be the same or different materials including at least one dopant material selected from the group consisting of K ₂ SeO _3.

The first doping layer 351 and the second doping layer 352 may be formed to a thickness of about 20 nm to about 40 nm. When the thickness of the first doping layer 351 and the second doping layer 352 is less than about 20 nm, a sufficient amount of the doping material may not be supplied into the light absorbing layer 300, If the thickness of the first doping layer 351 and the second doping layer 352 is greater than about 40 nm, the process efficiency may be lowered.

Solar cell according to the embodiment using at least one dopant material selected from the group consisting of _{Na 2 Se, K2 S e,} NaSe 2 O 3, K 2 SeO 3, Na 2 Se, K2 S e, NaSe 2 O 3 and K ₂ SeO ₃ So that the alkali material can be supplied into the light absorbing layer.

Accordingly, it is possible to remove the fluorine material remaining in the conventional NaF or KF or the like, thereby reducing the impurity content on the surface of the light absorption layer.

In addition, selenium of the doping material can compensate for the loss of selenium in the light absorbing layer that may occur during the process. In addition, by adjusting the band gap and the surface roughness by adjusting the concentration of sulfur and selenium, it is possible to reduce defects when depositing the buffer layer to be deposited later.

Therefore, the solar cell according to the embodiment can have overall improved efficiency and reliability.

The buffer layer 400 may be disposed on the light absorption layer 300. In detail, the buffer layer 400 may be disposed on the doping layer 350.

A high resistance buffer layer (not shown) may be further disposed on the buffer layer 400. The high-resistance buffer layer may include zinc oxide (i-ZnO) that is not doped with impurities. The energy band gap of the high resistance buffer layer may be about 3.1 eV to 3.3 eV.

Second through holes (TH2) may be formed on the buffer layer (400). The second through holes (TH2) may be an open region that exposes one surface of the rear electrode layer (200). The second through grooves TH2 may have a shape extending in one direction when viewed in a plan view.

The buffer layer 400 may be defined as a plurality of buffer layers by the second through holes TH2. That is, the buffer layer 400 may be divided into the buffer layers by the second through-holes TH2.

The front electrode layer 500 may be disposed on the buffer layer 400. The front electrode layer 500 may be a transparent conductive layer. In addition, the resistance of the front electrode layer 500 may be higher than the resistance of the rear electrode layer 500.

The front electrode layer 500 may include an oxide. Examples of the material used for the front electrode layer 500 include Al doped ZnC (indium zinc oxide), indium zinc oxide (IZO), indium tin oxide (ITO) And the like.

The front electrode layer 500 may include connecting portions 600 positioned inside the second through holes TH2 and connected to the rear electrode layer 200. [

Third through holes (TH3) may be formed in the front electrode layer (500). The third through holes TH3 may pass through the rear electrode layer 200, the light absorbing layer 300, the buffer layer 400, and the front electrode layer 500. [ Accordingly, one surface of the rear electrode layer 200 may be exposed by the third through holes TH3.

The third through grooves TH3 may be formed at positions adjacent to the second through grooves TH2. More specifically, the third through grooves TH3 may be disposed beside the second through grooves TH2. That is, when viewed in plan, the third through grooves TH3 may be arranged next to the second through grooves TH2. The third through grooves TH3 may have a shape extending in the first direction.

The front electrode layer 500 may be divided into a plurality of front electrodes by the third through holes TH3. That is, the front electrodes may be defined by the third through holes TH3.

The front electrodes may have a shape corresponding to the rear electrodes. That is, the front electrodes may be arranged in a stripe form. Alternatively, the front electrodes may be arranged in a matrix form.

In addition, a plurality of solar cells C1, C2, ... can be defined by the third through holes TH3. More specifically, the solar cells (C1, C2, ...) can be defined by the second through grooves (TH2) and the third through grooves (TH3). That is, the solar cell according to the embodiment can be divided into the solar cells (C1, C2, ...) by the second through grooves TH2 and the third through grooves TH3. The solar cells C1, C2, ... may be connected to each other in a second direction intersecting with the first direction. That is, current can flow in the second direction through the solar cells C1, C2, ....

That is, the solar cell panel 10 includes the support substrate 100 and the solar cells C1, C2,. The solar cells C1, C2, ... are disposed on the support substrate 100 and are spaced apart from each other. In addition, the solar cells C1, C2, ... may be connected in series with each other by the connection portions 600.

The connection portions 600 may be inserted into the second through-holes TH2. The connection portions 600 may extend downward from the front electrode layer 500 and may be connected to the rear electrode layer 200. For example, the connection portions 600 may extend from the front electrode of the first cell C1 and may be connected to the rear electrode of the second cell C2.

Accordingly, the connection portions 600 can connect adjacent solar cells. More specifically, the connection portions 600 may connect the front electrode and the rear electrode included in the adjacent solar cells, respectively.

The connection part 600 may be formed integrally with the front electrode layer 600. That is, the material used for the connection part 600 may be the same as the material used for the front electrode layer 500.

Hereinafter, a solar cell module to which the solar cell according to the embodiments is applied will be described with reference to FIG.

5, a solar cell module according to an embodiment includes a solar cell 1000, a plurality of frames 4000 that house the solar cell 1000, a protection layer (not shown) disposed on the solar cell 1000, (2000), and an upper substrate (3000) disposed on the protective layer (2000).

The protective layer 2000 is integrated with the solar cell 1000 by a lamination process while being disposed on the top of the solar cell 1000 to prevent corrosion due to moisture penetration and protect the solar cell 1000 from impact do. The protective layer 2000 may be made of a material such as ethylene vinyl acetate (EVA).

The upper substrate 3000 positioned on the protective layer 2000 is made of tempered glass having high transmittance and excellent breakage-preventing function. At this time, the tempered glass may be a low iron tempered glass having a low iron content.

The features, structures, effects and the like described in the foregoing embodiments are included in at least one embodiment of the present invention and are not necessarily limited to one embodiment. Further, the features, structures, effects, and the like illustrated in the embodiments may be combined or modified in other embodiments by those skilled in the art to which the embodiments belong. Therefore, it should be understood that the present invention is not limited to these combinations and modifications.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is clearly understood that the same is by way of illustration and example only and is not to be construed as limiting the scope of the present invention. It can be seen that various modifications and applications are possible. For example, each component specifically shown in the embodiments may be modified and implemented. It is to be understood that the present invention may be embodied in many other specific forms without departing from the spirit or essential characteristics thereof.

Claims (7)

A support substrate;
A rear electrode layer disposed on the supporting substrate;
A light absorbing layer disposed on the rear electrode layer;
A doping layer disposed on the light absorbing layer;
A buffer layer disposed on the doped layer; And
And a front electrode layer disposed on the buffer layer,
Wherein the doping layer comprises at least one element selected from the group consisting of sodium (Na), potassium (K), selenium (Se), and sulfur (S). The method according to claim 1,
The doped layer is _{Na 2 Se, K2 S e,} NaSe 2 O 3, K 2 SeO 3, Na 2 Se, K2 S e, NaSe 2 O 3 and K ₂ SeO solar cell including at least one of the _three. The method according to claim 1,
Wherein the doping layer is disposed at a thickness of 20 nm to 40 nm. The method according to claim 1,
Wherein the doping layer is formed of at least two layers containing different materials. The method according to claim 1,
The doping layer
A first doping layer disposed on the light absorbing layer;
And a second doping layer disposed on the first doping layer,
The first doped layer and the second doped layer is _{Na 2 Se, K2 S e,} NaSe 2 O 3, K 2 SeO 3, Na 2 Se, K2 S e, NaSe at least one of the ₂ O ₃ and K ₂ SeO ₃ ≪ / RTI > 6. The method of claim 5,
Wherein at least one of the first doping layer and the second doping layer has a thickness of 20 nm to 40 nm. The method according to claim 1,
Wherein the light absorbing layer has a lower concentration of sodium or potassium as it extends toward the rear electrode layer.

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