KR101784440B1 - Thin film solar cell - Google Patents

Abstract

The present invention relates to a thin film solar cell.
An example of a thin film solar cell according to the present invention includes a substrate; A first electrode disposed on the substrate; A second electrode disposed on the first electrode; And a photoelectric conversion unit disposed between the first electrode and the second electrode and converting light into incident light, and the second electrode includes a plurality of microlenses.

Description

Thin Film Solar Cell {THIN FILM SOLAR CELL}

The present invention relates to a thin film solar cell.

Recently, as energy resources such as oil 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.

Typical solar cells have a semiconductor portion that forms a p-n junction by different conductive types, such as p-type and n-type, and electrodes connected to semiconductor portions of different conductivity types, respectively.

When light is incident on such a solar cell, a plurality of electron-hole pairs are generated in the semiconductor, and the generated electron-hole pairs are separated into electrons and holes, respectively, so that electrons move toward the n- And moves toward the semiconductor portion. The transferred electrons and holes are collected by the different electrodes connected to the p-type semiconductor portion and the n-type semiconductor portion, respectively, and the electrodes are connected by a wire to obtain electric power.

An object of the present invention is to provide a thin film solar cell with improved efficiency.

An example of a thin film solar cell according to the present invention includes a substrate; A first electrode disposed on the substrate; A second electrode disposed on the first electrode; And a photoelectric conversion unit disposed between the first electrode and the second electrode and converting light into incident light, and the second electrode includes a plurality of microlenses.

Here, the second electrode includes a transparent electrode layer containing a light-transmitting conductive material and a metal electrode layer containing a light-permeable conductive material, wherein the plurality of microlenses are located between the transparent electrode layer and the metal electrode layer, May include a conductive material. Here, the transparent electrode layer is in contact with the photoelectric conversion portion, and the metal electrode layer is in contact with the transparent electrode layer and the plurality of microlenses.

Here, the plurality of microlenses may comprise a resin-based material, for example, the resin-based material may comprise at least one of a polymer or monomeric series of carbon polymers or monomers or glycerin.

The plurality of microlenses may include a first surface contacting the transparent electrode layer and a second surface contacting the metal electrode layer, the second surface including a curved surface, and the first surface including a plurality of irregularities.

Further, in the plurality of microlenses, the thickness of the edge portion may be smaller than the thickness of the center portion.

The first electrode includes a plurality of irregularities, and the diameter of at least one of the plurality of microlenses may be greater than the interval between protrusions of the irregularities included in the first electrode, and the maximum thickness of at least one of the plurality of microlenses May be greater than the projecting height of the concave and convex portions included in the first electrode.

For example, the diameter of each of the plurality of microlenses may be between 1 탆 and 15 탆, and the ratio of the maximum thickness of each of the plurality of lenses to the diameter of each of the plurality of microlenses may be between 1: 0.2 and 0.5.

The ratio of the total area occupied by the first surface of the plurality of microlenses to the total area of the transparent electrode layer may be between 1: 0.25 and 0.75.

In addition, of the plurality of microlenses, two microlenses located in adjacent different rows may be located in the same column or in different columns.

The plurality of microlenses may include a first lens formed with a first diameter and a second lens formed with a second diameter smaller than the first diameter, and the second lens may be positioned between the first lenses.

Here, the first diameter may be between 1.5 and 2.5 times the second diameter.

Further, the photoelectric conversion portion may have at least one p-i-n structure including a p-type semiconductor layer, an intrinsic (i) semiconductor layer, and an n-type semiconductor layer.

The transparent electrode layer may be formed of at least one of zinc oxide (ZnOx), tin oxide (SnOx), indium oxide (InOx), silicon oxide (SiOx), zinc boron oxide (ZnO: B, BZO), and aluminum zinc oxide And the like.

The thickness of the transparent electrode layer may be between 50 nm and 1.5 mu m.

In the solar cell according to the present invention, since the second electrode includes a plurality of microlenses, internal reflection effectively occurs by the microlenses. Therefore, the photoelectric conversion efficiency of the photoelectric conversion portion is further improved.

1 is a view for explaining an example of a thin film solar cell according to the present invention.
2A to 2C are views for explaining an example in which a lens of a thin film solar cell according to the present invention is arranged above a transparent electrode layer.
3 is a view for explaining an example in which the photoelectric conversion unit PV of the solar cell module according to the present invention includes a double junction solar cell or a pinpin structure.
4 is a view for explaining an example of a case where the solar cell module according to the present invention includes a triple junction solar cell or a pinpinpin structure.
5A to 5E are views for explaining an example of a method of manufacturing a thin film solar cell according to the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those skilled in the art can easily carry out the present invention. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

In the drawings, the thickness is enlarged to clearly represent the layers and regions. When a layer, film, region, plate, or the like is referred to as being "on" another portion, it includes not only the case directly above another portion but also the case where there is another portion in between. Conversely, when a part is "directly over" another part, it means that there is no other part in the middle. Also, when a part is formed as "whole" on the other part, it means not only that it is formed on the entire surface (or the front surface) of the other part but also not on the edge part.

1 is a view for explaining an example of a thin film solar cell according to the present invention.

1, an example of a thin film solar cell according to the present invention includes a substrate 100, a first electrode 110, a photoelectric conversion unit PV, and a second electrode 130, (130) includes a plurality of microlenses (135) spaced apart from each other.

In FIG. 1, the structure of the photoelectric conversion unit PV is a p-i-n structure from the incident plane. However, it is also possible that the structure of the photoelectric conversion unit PV becomes an n-i-p structure from the incident plane. However, for convenience of description, the structure of the photoelectric conversion portion PV is a p-i-n structure from the incident side will be described below as an example.

Here, the substrate 100 may be made of a substantially transparent nonconductive material, such as glass or plastic, in order to allow the incident light to reach the photoelectric conversion unit PV more effectively.

The first electrode 110 is disposed on top of the substrate 100 and contains a substantially light-transmissive conductive material to increase the transmittance of the incident light.

For example, the conductive material forming the first electrode 110 may be indium tin oxide (ITO), tin oxide (SnO ₂ ), AgO, ZnO- (ZnO), or the like having high light transmittance and high electrical conductivity Ga ₂ O ₃ or Al ₂ O ₃ ), fluorine tin oxide (FTO), boron zinc oxide (ZnO: B, BZO) and aluminum zinc oxide (ZnO: Al, AZO) .

The first electrode 110 may be electrically connected to the photoelectric conversion unit PV. Accordingly, the first electrode 110 can collect and output one of the carriers generated by the incident light, for example, holes.

In addition, a plurality of irregularities having a random pyramid structure may be formed on the upper surface of the first electrode 110. That is, the first electrode 110 has a texturing surface.

By texturing the surface of the first electrode 110 as described above, it is possible to reduce the reflection of the incident light and increase the light absorption rate, thereby improving the efficiency of the solar cell.

Next, the second electrode 130 is disposed on the upper portion of the first electrode 110 and is disposed on the photoelectric conversion unit PV. In order to increase the recovery efficiency of the power generated by the photoelectric conversion unit PV, It can include excellent metal materials.

In addition, the second electrode 130 is electrically connected to the photoelectric conversion unit PV, and can collect and output one of carriers, e.g., electrons, generated by the incident light.

The second electrode 130 includes a transparent electrode layer 131 and a metal electrode layer 133. The transparent electrode layer 131 is positioned between the photoelectric conversion unit PV and the metal electrode layer 133 and minimizes the contact resistance between the photoelectric conversion unit PV and the metal electrode layer 133. The metal electrode layer 133 Serves to collect the carriers generated in the photoelectric conversion unit PV through the transparent electrode layer 131. [ Here, the transparent electrode layer 131 may be omitted in some cases.

The second electrode 130 includes a plurality of microlenses 135 as described above. The plurality of microlenses 135 include a light-transmissive nonconductive material, and reflect and scatter incident light. A detailed description thereof will be described later.

Next, the photoelectric conversion unit PV is disposed between the first electrode 110 and the second electrode 130, and functions to convert light incident from the outside through the incident surface of the substrate 100 into electricity.

Such a photoelectric conversion portion PV includes a p-type semiconductor layer 120p, an intrinsic (i-type) semiconductor layer 120i, and an n-type semiconductor layer 120n from the incident surface of the substrate 100 .

Here, the p-type semiconductor layer 120p can be formed by using a gas containing an impurity of a trivalent element such as boron, gallium, or indium in a source gas containing silicon (Si).

The intrinsic (i) semiconductor layer can reduce the recombination rate of carriers and absorb light. The intrinsic semiconductor layer 120i absorbs incident light and can generate carriers such as electrons and holes.

The intrinsic semiconductor layer 120i may include an amorphous silicon material (a-si) or a microcrystalline silicon (mc-Si) material.

The n-type semiconductor layer 120n can be formed using a gas containing an impurity of a pentavalent element such as phosphorus (P), arsenic (As), antimony (Sb) or the like in a source gas containing silicon.

The photoelectric conversion unit PV may be formed by chemical vapor deposition (CVD) such as plasma enhanced chemical vapor deposition (PECVD).

1, a doping layer such as the p-type semiconductor layer 120p and the n-type semiconductor layer 120n of the photoelectric conversion portion PV is formed to have a pn junction with the intrinsic semiconductor layer 120i therebetween .

In this structure, when light is incident on the p-type semiconductor layer 120p, the p-type semiconductor layer 120p and the n-type semiconductor layer 120n having a relatively high doping concentration inside the intrinsic semiconductor layer 120i cause depletion a depletion is formed, whereby an electric field can be formed. Due to the photovoltaic effect, electrons and holes generated in the intrinsic semiconductor layer 120i as the light absorbing layer are separated by the contact potential difference and are moved in different directions. For example, holes may move toward the first electrode 110 through the p-type semiconductor layer 120p and electrons may move toward the second electrode 130 through the n-type semiconductor layer 120n. Power can be produced in this way.

The plurality of microlenses 135 included in the second electrode 130 will be described in more detail as follows.

1, the second electrodes 130 may further include a plurality of microlenses 135 arranged apart from each other and including a light-transmitting non-conductive material, and the plurality of microlenses 135 may be transparent And may be located between the electrode layer 131 and the metal electrode layer 133. It is possible to form a plurality of microlenses between the substrate 100 and the first electrode 110. In this case, The first electrode and the photoelectric conversion unit must be deposited. Therefore, thermal deformation of the microlens occurs due to heat generated during the deposition process of the first electrode and the photoelectric conversion unit, and impurities are generated in the device by out- So that the device is deteriorated.

In order to prevent a leakage current from being generated due to cracks in the device due to the microlenses, there is a great limitation in designing the shape (size, thickness, etc.) of the microlenses.

In addition, when the microlenses are formed of a polymer-based material, the degree of crystallization of the first electrode is lowered when the first electrode is formed, and the conductivity of the first electrode is lowered. Due to the infiltration of impurities from the microlenses, And the like.

In order to solve the above problems, in the present invention, a plurality of microlenses 135 are positioned between the transparent electrode layer 131 and the metal electrode layer 133.

That is, if the plurality of microlenses 135 are positioned between the transparent electrode layer 131 and the metal electrode layer 133, the first electrode 110 and the photoelectric conversion portion PV are deposited, It is possible to prevent deterioration of the device due to the high-temperature process, and it is possible to form the shape of the microlenses by various methods, and it is possible to prevent the conductivity of the first electrode from being lowered.

It is also possible to obtain an effect of more efficiently reflecting and scattering the light of the middle wavelength and the longer wavelength band of 700 nm or more transmitted through the photoelectric conversion unit PV.

Here, the transparent electrode layer 131 is in contact with the photoelectric conversion unit PV and includes an uneven surface as shown in FIG. 1, and may contain a light-transmitting conductive material that transmits light. In addition, the metal electrode layer 133 may contain a light-transmissive conductive material that is in contact with the transparent electrode layer 131 and the plurality of microlenses 135, and does not transmit light.

As shown in FIG. 1, the plurality of microlenses 135 reflects incident light transmitted through the photoelectric conversion unit PV back into the photoelectric conversion unit PV so that the incident light is scattered, There is an effect of expanding the optical path in the conversion section PV.

Thus, the photoelectric conversion efficiency of the photoelectric conversion unit (PV) can be improved by further improving the light absorption rate in the photoelectric conversion unit (PV).

The transparent electrode layer 131 may be formed of indium tin oxide (ITO), tin oxide (SnO ₂ ), AgO, ZnO (Ga ₂ O ₃ or Al ₂ O _{3 )} , fluorine tin oxide (Al 2 O 3), aluminum oxide (FTO), silicon oxide (SiO x), boron zinc oxide (ZnO: B, BZO) and aluminum zinc oxide .

The thickness of the transparent electrode layer 131 is preferably in the range of 50 nm to 1.5 占 퐉 in consideration of the contact area with the metal electrode layer 133 and the series resistance of the device.

In addition, the metal electrode layer 133 may be formed of at least one of silver (Ag) or aluminum (Al) having good electrical conductivity, and may be formed as a single layer or a multilayer. And may include at least one of a polymer or monomer-based carbon polymer or monomer or glycerin capable of being subjected to a printing process.

The plurality of microlenses 135 may include a first surface 135F1 that is in contact with the transparent electrode layer 131 and a second surface 135F2 that is in contact with the metal electrode layer 133 as shown in FIG. .

Here, the first surface 135F1 of the lens 135 includes irregularities corresponding to the uneven surface of the transparent electrode layer 131, the second surface 135F2 includes a curved surface, and the edge 135F1 of the lens 135 The thickness of the second surface 135F2 is smaller than the thickness of the central portion of the lens 135 so that the second surface 135F2 can have a convex shape from the first surface 135F1 and a shape of the concave lens 135 with respect to the direction in which light is incident . 1, the light having passed through the photoelectric conversion unit PV is reflected and scattered by the inclined surface of the second surface of the microlens 135, and is incident again into the photoelectric conversion unit PV, do.

The diameter or width W135 of at least one of the plurality of microlenses 135 may be greater than the interval W110 between the protrusions of the irregularities included in the first electrode 110, The height H135 of at least one of the first electrodes 110 may be greater than the height H110 of protrusions and protrusions included in the first electrode 110. [

Accordingly, the plurality of microlenses 135 reflects the light having the middle or long wavelength band of 700 nm or more in the light transmitted through the photoelectric conversion unit PV back into the photoelectric conversion unit PV, so that the incident light is scattered. Thereby enlarging the optical path in the photoelectric conversion unit PV.

Accordingly, the photoelectric conversion efficiency of the thin film solar cell can be further improved.

More specifically, the size of the irregularities of the first electrode 110 formed on the interface with the photoelectric conversion unit PV is substantially equal to or smaller than 1 占 퐉, that is, the interval W110 between the projections of the irregularities is 1 占 퐉 or less, Concave and convex portions having a projection height H110 of 1 m or less are formed.

The irregularities of the first electrode 110 having such a size can cause scattering of light of 400 to 700 nm in the 400 to 1100 nm light incident on the thin film solar cell, The light path can be increased so that the light can be absorbed well. However, for the remaining 700 nm to 1100 nm light, the degree of roughness of the unevenness is too small compared to the wavelength of the light, .

In this case, the amount of light absorbed in the photoelectric conversion unit (PV) is significantly reduced due to the relatively short optical path of light of 700 nm to 1100 nm, and the photoelectric conversion efficiency of the thin film solar cell may be lowered.

However, like the thin film solar cell according to the present invention, the second electrode 130 includes a plurality of microlenses 135 including a light-transmitting material, and at least one of the plurality of microlenses 135 has a diameter or width When the degree of roughness of the second electrode 130 is increased by making the width W135 and the maximum thickness H135 larger than the size of the irregularities included in the first electrode 110, It is possible to cause reflection and scattering to occur well, and the light absorption rate in the photoelectric conversion portion PV can be further increased.

The diameter or the width W135 of each of the plurality of microlenses 135 may be formed to be between 1 탆 and 15 탆, for example.

The ratio of the width W135 of the microlenses 135 to the maximum thickness H135 of each of the microlenses 135 may be between 1: 0.2 and 0.5. This portion scatters light in the microlens 135 and the part that increases the light path of the light in the photoelectric converter PV is a curved surface inclined surface included in the second surface 135F2 of the microlens 135, This is because the maximum thickness H135 of each of the microlenses 135 for appropriately forming such a curved surface is between 0.2 and 0.5 times the width W135 of the microlens 135.

More specifically, the reason why the maximum thickness H135 of the microlenses 135 with respect to the width or the diameter W135 of the microlens 135 is larger than 1: 0.2 is to obtain a minimum light scattering effect, : 0.5 or less, in order to prevent the amount of light absorbed by the microlens 135 itself from becoming relatively large when the maximum thickness of the microlens is excessively large.

Here, the maximum thickness H135 of the microlenses 135 means the thickness of the thickest portion of one microlens 135.

1, a description has been given of an example of a thin film solar cell including a plurality of microlenses 135 inside a second electrode 130. Hereinafter, a description will be given of a case where a metal electrode layer 133 is removed The manner in which the plurality of lenses 135 are arranged on the transparent electrode layer 131 when the rear surface of the thin film solar cell is viewed will be described.

2A to 2C are views for explaining an example in which a lens of a thin film solar cell according to the present invention is arranged above a transparent electrode layer.

2A to 2C show an example of a configuration in which a plurality of microlenses 135 are arranged on the transparent electrode layer 131, but the invention is not limited thereto.

Of the plurality of microlenses 135, two microlenses 135 located in adjacent different rows may be located in the same column or in different columns.

For example, as shown in FIG. 2A, two microlenses 135a and 135b located in adjacent different rows 135D1 and 135D2 may be arranged in the same row 135H1 and arranged in a lattice form, As shown in FIG. 2B, the two lenses 135a and 135b located in adjacent different rows 135D1 and 135D2 may be located in different rows 135H1 and 135H2.

The plurality of microlenses 135 according to the present invention includes a first microlens 135R1 having a first width and a second microlens 135R2 having a second width smaller than the first microlens 135R1, . ≪ / RTI > Here, the first width may be between 1.5 and 2.5 times the second width.

In this case, as shown in FIG. 2C, the second microlenses 135R2 may be positioned between the first microlenses 135R1. Alternatively, the first microlenses 135R1 and 135R2 may be arranged such that the first microlenses 135R1 and the second microlenses 135R2 are alternately arranged in a lattice form It is possible.

In this case, the first microlens 135R1 having the first width having a relatively large diameter reflects and scatters the light having the long wavelength band, and the second microlens 135R2 having the second width having a relatively small diameter It functions to reflect and scatter light of short wavelength band. By forming the width of the lens 135 in this way, it is possible to more accurately reflect and scatter the light of the middle wavelength band and the long wavelength band of 700 nm or more, thereby further improving the photoelectric conversion efficiency of the thin film solar cell .

1 and 2A to 2C, the ratio of the area occupied by the first surface 135F1 of the microlens 135 in contact with the transparent electrode layer 131 to the total area of the transparent electrode layer 131 is 1 : Between 0.25 and 0.75.

The reason why the ratio of the area occupied by the first surface 135F1 of the microlens 135 to the total area of the transparent electrode layer 131 is 1: 0.25 or more is that the microlenses 135 cause the medium and long wavelength So as to minimize the reflection and scattering effects.

The reason why the ratio of the area occupied by the first surface 135F1 of the microlens 135 to the total area of the transparent electrode layer 131 is 1: 0.75 or less is that the microlens 135 includes a non- The contact resistance between the transparent electrode layer 131 and the metal electrode layer 133 is minimized.

More specifically, the transparent electrode layer 131 and the metal electrode layer 133 contain a conductive material, and the microlens 135 includes a nonconductive material. In this case, when the area occupied by the plurality of microlenses 135 located between the transparent electrode layer 131 and the metal electrode layer 133 is increased, the contact resistance between the transparent electrode layer 131 and the metal electrode layer 133 is relatively increased Can be increased.

Therefore, even if the area occupied by the plurality of microlenses 135 increases, the ratio of the area occupied by the first surface 135F1 of the microlens 135 to the total area of the transparent electrode layer 131 is 1: 0.75 The electrical resistance can be minimized when the carriers collected in the transparent electrode layer 131 move to the metal electrode layer 133.

Although the present invention has been described above with reference to the case where each cell of the solar cell module is a single junction module, the present invention is also applicable to a case where each cell of the solar cell module is a double junction solar cell or a triple junction solar cell Can be applied.

3 is a view for explaining an example in which the photoelectric conversion unit PV of the solar cell module according to the present invention includes a double junction solar cell or a p-i-n-p-i-n structure.

Hereinafter, the description of the parts overlapping with those described in detail above will be omitted

As shown in FIG. 3, the photoelectric conversion unit PV of the double junction solar cell may include a first photoelectric conversion unit PV1 and a second photoelectric conversion unit PV2.

3, the double junction solar cell has a first p-type semiconductor layer PV1-p, a first i-type semiconductor layer PV1-i, a first n-type semiconductor layer PV1-n, The second p-type semiconductor layer PV2-p, the second i-type semiconductor layer PV2-i, and the second n-type semiconductor layer PV2-n may be sequentially stacked.

The first i-type semiconductor layer PV1-i can mainly absorb light in a short wavelength band to generate electrons and holes.

In addition, the second i-type semiconductor layer PV2-i can mainly absorb light of a longer wavelength band than the short wavelength band to generate electrons and holes.

As described above, a solar cell having a double junction structure can have high efficiency because it absorbs light in a short wavelength band and a long wavelength band to generate a carrier.

3, the first i-type semiconductor layer PV1-i of the first photoelectric conversion unit PV1 includes an amorphous silicon material (a-Si), and the second photoelectric conversion unit PV1- The second i-type semiconductor layer PV2-i of the conversion section PV2 may include an amorphous silicon material (a-SiGe) containing a germanium material.

In such a double junction solar cell, a plurality of microlenses 135 as described above with reference to FIG. 1 and FIGS. 2A to 2C are included in the second electrode 130, And Figs. 2A to 2C.

Therefore, a detailed description of the plurality of microlenses 135 applied to the double junction solar cell is the same as that described with reference to FIG. 1 and FIGS. 2A to 2C, and thus will not be described.

In the double junction thin film solar cell in which the plurality of microlenses 135 are included in the second electrode 130, the plurality of microlenses 135 can more efficiently reflect and refract light in the middle and long wavelength band of 700 nm or more. So that the efficiency of the thin film solar cell can be further improved.

4 is a view for explaining an example in which the solar cell module according to the present invention includes a triple junction solar cell or a p-i-n-p-i-n-p-i-n structure.

Hereinafter, the description of the parts overlapping with those described in detail above will be omitted.

4, the photoelectric conversion unit PV of the thin film solar cell includes a first photoelectric conversion unit PV1, a second photoelectric conversion unit PV2, and a third photoelectric conversion unit PV1 from the incident surface of the substrate 100, (PV3) may be arranged in order.

Here, the first photoelectric conversion unit PV1, the second photoelectric conversion unit PV2, and the third photoelectric conversion unit PV3 may be formed in a pin structure, respectively, so that the first p-type semiconductor layer The first intrinsic semiconductor layer PV1-p, the first intrinsic semiconductor layer PV1-i, the first n-type semiconductor layer PV1-n, the second p-type semiconductor layer PV2- The second n-type semiconductor layer PV2-n, the third p-type semiconductor layer PV3-p, the third intrinsic semiconductor layer PV3-i, and the third n-type semiconductor layer PV3- .

Here, the first intrinsic semiconductor layer PV1-i, the second intrinsic semiconductor layer PV2-i, and the third intrinsic semiconductor layer PV3-i may be variously implemented.

4, the first intrinsic semiconductor layer PV1-i includes an amorphous silicon (a-Si) material and the second intrinsic semiconductor layer PV2-i comprises an amorphous (germanium) Silicon (a-SiGe) material, and the third intrinsic semiconductor layer PV3-i includes a microcrystalline silicon (μc-SiGe) material containing a germanium (Ge) material.

Here, not only the second intrinsic semiconductor layer PV2-i but also the third intrinsic semiconductor layer PV3-i can be doped with a germanium (Ge) material as an impurity.

Here, the content ratio of germanium (Ge) contained in the third intrinsic semiconductor layer (PV3-i) may be larger than the content ratio of germanium (Ge) contained in the second intrinsic semiconductor layer (PV2-i). This is because the band gap becomes smaller as the content ratio of germanium (Ge) increases. As the bandgap decreases, it is advantageous to absorb long wavelength light.

Therefore, by making the ratio of the content of germanium (Ge) contained in the third intrinsic semiconductor layer (PV3-i) larger than the ratio of the content of germanium (Ge) contained in the second intrinsic semiconductor layer (PV2-i) It is possible to more efficiently absorb light of a long wavelength in the semiconductor layer (PV3-i).

Alternatively, in the second example, the first intrinsic semiconductor layer PV1-i may include an amorphous silicon (a-Si) material, and the second intrinsic semiconductor layer PV2-i and the third intrinsic semiconductor layer PV3-i) may comprise a microcrystalline silicon (μc-Si) material. Here, the bandgap of the third intrinsic semiconductor layer PV3-i may be lowered by doping only germanium (Ge) material with impurities in the third intrinsic semiconductor layer PV3-i.

4, a first example, that is, a first intrinsic semiconductor layer PV1-i and a second intrinsic semiconductor layer PV2-i includes an amorphous silicon (a-Si) material, The ternary semiconductor layer PV3-i includes a microcrystalline silicon (μc-Si) material, and the second intrinsic semiconductor layer PV2-i and the third intrinsic semiconductor layer PV3- (Ge) material.

Here, the first photoelectric conversion unit PV1 can absorb light in a short wavelength band to produce electric power, and the second photoelectric conversion unit PV2 can absorb light in a middle band between a short wavelength band and a long wavelength band to produce electric power And the third photoelectric conversion unit PV3 can generate power by absorbing light of a long wavelength band.

Here, the thickness of the third intrinsic semiconductor layer PV3-i is thicker than the thickness of the second intrinsic semiconductor layer PV2-i, and the thickness of the second intrinsic semiconductor layer PV2- -i. < / RTI >

For example, the first intrinsic semiconductor layer PV1-i may be formed to a thickness of 100 to 150 nm, the second intrinsic semiconductor layer PV2-i may be formed to a thickness of 150 to 300 nm, The semiconductor layer PV3-i may be formed to a thickness of 1.5 mu m to 4 mu m.

This is to further improve the light absorptance in the long wavelength band in the third intrinsic semiconductor layer (PV3-i).

As described above, in the case of the triple junction solar cell as shown in FIG. 4, since the light of a wider band can be absorbed, the power production efficiency can be high.

In such a triple junction solar cell, a plurality of microlenses 135 as described above with reference to FIG. 1 and FIGS. 2A to 2C are included in the second electrode 130, And Figs. 2A to 2C.

Therefore, a detailed description of the plurality of microlenses 135 applied to the triple junction solar cell is the same as that described with reference to FIG. 1 and FIGS. 2A to 2C, and thus will not be described.

In the triple junction thin film solar cell in which the plurality of microlenses 135 are included in the second electrode 130, the plurality of microlenses 135 can more efficiently reflect and refract light in the middle and long wavelength band of 700 nm or more. So that the efficiency of the thin film solar cell can be further improved.

5A to 5E, a method of manufacturing a thin film solar cell having a plurality of lenses 135 in the second electrode 130 described above will be described.

5A to 5E are views for explaining an example of a method of manufacturing a thin film solar cell according to the present invention.

First, as shown in FIG. 5A, a first electrode 110 is formed on a substrate 100. The first electrode 110 may be formed on the upper surface of the substrate 100 by various methods such as an electroplating method, a sputtering method, an evaporation method, a low pressure chemical vapor deposition (LPCVD) A film forming method may be used.

5B, a p-i-n semiconductor layer is sequentially deposited on the first electrode 110 to form a photoelectric conversion portion PV. The photoelectric conversion unit PV may be formed by chemical vapor deposition (CVD) such as plasma enhanced chemical vapor deposition (PECVD).

Then, as shown in FIG. 5C, a transparent electrode layer 131 included in the second electrode 130 is formed on the photoelectric conversion unit PV. The transparent electrode layer 131 functions to minimize the contact resistance between the photoelectric conversion portion PV and the metal electrode layer 133, as described above.

The transparent electrode layer 131 may be formed by an electroplating method, a sputtering method, an evaporation method, a low pressure chemical vapor deposition (LPCVD) method, And the like can be used.

Then, as shown in FIG. 5D, a plurality of microlenses 135 are formed on the transparent electrode layer 131. The method of forming the plurality of microlenses 135 may be a printing method at a low temperature and may be formed in a dot shape. However, it is not necessarily limited thereto, and various other methods that can be adhered in a dot form may be used.

In order to form the plurality of micro lenses 135, a resin-based material, for example, a paste containing the above-mentioned carbon polymer or glycerin may be used. The average inclination of the curved surface portion formed on the second surface 135F2 of the first surface 135F2 can be controlled. For example, when the viscosity of the paste is increased, the average slope of the curved surface formed on the second surface 135F2 of the microlens 135 becomes relatively large, so that the maximum thickness H135 of the lens 135 is relatively large The average slope of the curved surface formed on the second surface 135F2 of the microlens 135 is relatively lowered and the maximum thickness H135 of the microlens 135 is lowered, Can have a relatively low value.

As described above, the present invention is characterized in that the second electrode 130 includes a plurality of microlenses 135 having a size larger than that of the irregularities formed in the first electrode 110, so that the reflection and scattering of light for the medium- and long- The effect can be improved.

5E, a metal electrode layer 133 is formed on a part of the transparent reflective layer exposed between the second surface 135F2 of the microlens 135 and the microlenses 135 to complete a thin film solar cell .

In the thin film solar cell according to the present invention, the microlens 135, which is larger than the irregularities of the first electrode 110, is included in the second electrode 130, so that the photoelectric conversion unit PV It is possible to eliminate the adverse effect that can be caused.

For example, when a plurality of microlenses 135 are formed in the upper part of the substrate 100 or in the upper part or the upper part of the first electrode 110, There is a high possibility that a crack is generated in the photoelectric conversion portion PV due to a relatively large and sharp sloped surface formed by the curved surface of the photoelectric conversion portion PV. When the lens 135 is formed in the first electrode 110, the temperature of the first electrode 110 and the photoelectric conversion unit PV in the high temperature process (for example, the deposition temperature of the first electrode is 300 ° C to 350 ° C and the deposition temperature of the photoelectric conversion portion is 150 ° C to 250 ° C).

However, in the case where the microlens 135 is formed in the second electrode 130 as in the present invention, since the microlens 135 is formed after the photoelectric conversion unit PV is formed, There is no possibility that cracks will be formed in the first electrode 110 and the micro lens 135 due to the high temperature process during the formation of the first electrode 110 and the photoelectric conversion portion PV. Further, since the step of forming the metal electrode layer 133 is a low-temperature process after the formation of the microlenses 135, the properties of the microlenses 135 are hardly degraded.

In the case where the microlens 135 is formed in the second electrode 130 as in the present invention, it is not necessary to consider adverse effects on the photoelectric conversion portion PV. Therefore, the width, diameter, and thickness of the microlens 135 There is an advantage that it can be formed with free reinforcement.

As described above, in the thin film solar cell according to the present invention, the plurality of microlenses 135 are formed in the second electrode 130, so that the light in the middle and long wavelength bands can be more efficiently absorbed by the photoelectric conversion unit PV The microlenses 135 are formed in the second electrode 130 in such a manner that the microlenses 135 can be maintained in good condition during the manufacturing process, The microlens 135 can be formed without adversely affecting the photoelectric conversion portion PV at all.

In the thin film solar cell module according to the present invention, the photoelectric conversion unit (PV) is made of CdTe (Cadmium telluride), and the photoelectric conversion unit (PV) ), CIGS (Copper Indium Gallium Selenide) or Cadmium Sulfide (CdS), etc., and the photoelectric conversion portion PV may be applied to a porous titanium dioxide (TiO ₂ ) Cadmium sulfide (CdS) adsorbed, and may include organic or polymeric materials.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, Of the right.

Claims (20)

Board;
A first electrode disposed on the substrate, the first electrode including a plurality of irregularities;
A second electrode disposed on the first electrode; And
And a photoelectric conversion unit disposed between the first electrode and the second electrode, for converting incident light into electric power,
Wherein the second electrode comprises a plurality of microlenses spaced apart from the substrate,
Wherein the microlens includes a first surface located on the side of the photoelectric conversion portion and a second surface opposite to the first surface,
Wherein the first surface of the microlens includes an irregular surface corresponding to the plurality of irregularities,
Wherein the second surface of the microlens is formed of a lens surface having a shape different from that of the plurality of irregularities and different sizes. The method according to claim 1,
Wherein the second electrode includes a transparent electrode layer containing a light-transmitting conductive material and a metal electrode layer containing a light-permeable conductive material,
Wherein the plurality of microlenses are disposed between the transparent electrode layer and the metal electrode layer and include a light-transmitting nonconductive material. 3. The method of claim 2,
Wherein the transparent electrode layer is in contact with the photoelectric conversion portion, and the metal electrode layer is in contact with the transparent electrode layer and the plurality of microlenses. The method according to claim 1,
Wherein the plurality of microlenses comprise resin-based materials. 5. The method of claim 4,
Wherein the resin-based material comprises at least one of a polymer or monomer-based carbon polymer or unit or glycerin. 3. The method of claim 2,
The first surface of the microlens being in contact with the transparent electrode layer, the second surface being in contact with the metal electrode layer,
And the second surface includes a curved surface. delete The method according to claim 1,
Wherein a thickness of the edge portion of the plurality of microlenses is smaller than a thickness of the center portion. The method according to claim 1,
Wherein a diameter of at least one of the plurality of microlenses is larger than a distance between protrusions of the concave and convex included in the first electrode. The method according to claim 1,
Wherein a maximum thickness of at least one of the plurality of microlenses is larger than a projecting height of the concavo-convex included in the first electrode. The method according to claim 1,
Wherein the diameter of each of the plurality of microlenses is between 1 탆 and 15 탆. The method according to claim 1,
Wherein a ratio of a maximum thickness of each of the plurality of lenses to a diameter of each of the plurality of microlenses is within a range of 1: 0.2 to 0.5. The method according to claim 6,
Wherein the ratio of the total area occupied by the first surface of the plurality of microlenses to the total area of the transparent electrode layer is 1: 0.25 to 0.75. The method according to claim 1,
Wherein two microlenses located in adjacent rows of the plurality of microlenses are located in the same column or in different columns. The method according to claim 1,
Wherein the plurality of microlenses comprises a first lens formed with a first diameter and a second lens formed with a second diameter smaller than the first diameter. 16. The method of claim 15,
And the second lens is located between the first lens. 16. The method of claim 15,
Wherein the first diameter is between 1.5 and 2.5 times the second diameter. The method according to claim 1,
Wherein the photoelectric conversion portion has at least one pin structure including a P-type semiconductor layer, an intrinsic (i) semiconductor layer, and an n-type semiconductor layer. 3. The method of claim 2,
The transparent electrode layer may be formed of one of zinc oxide (ZnOx), tin oxide (SnOx), indium oxide (InOx), silicon oxide (SiOx), zinc boron oxide (ZnO: B, BZO) and aluminum zinc oxide A thin film solar cell comprising at least any one material. 3. The method of claim 2,
Wherein the transparent electrode layer has a thickness of 50 nm to 1.5 占 퐉.

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