KR101411996B1

KR101411996B1 - High efficiency solar cells

Info

Publication number: KR101411996B1
Application number: KR1020080080214A
Authority: KR
Inventors: 위순임
Original assignee: 주식회사 뉴파워 프라즈마
Priority date: 2008-08-16
Filing date: 2008-08-16
Publication date: 2014-06-26
Also published as: KR20100021539A

Abstract

The present invention relates to an improved high efficiency solar cell capable of achieving high energy conversion efficiency by preventing recombination of electron-hole pairs by applying a bias voltage to a solar cell so that charges generated by light are rapidly collected and collected. The high efficiency solar cell of the present invention includes a photovoltaic power generation unit for generating charges by light absorption, first and second electrodes provided in the photovoltaic power generation unit and having polarities different from each other, And the charge generated by the photovoltaic generation unit is collected by being flowed more quickly toward the first and second electrodes by the bias voltage applied to the bias electrode, thereby preventing the recombination of the electron-hole pairs High energy conversion efficiency can be obtained.

Solar cell, efficiency, bias, recombination

Description

[0001] HIGH EFFICIENCY SOLAR CELLS [0002]

The present invention relates to a solar cell, and more particularly, to a solar cell capable of achieving high energy conversion efficiency by maximally preventing recombination of electron-hole pairs by applying a bias voltage to a solar cell so that charges generated by light are rapidly collected and collected To an improved high efficiency solar cell.

Solar power generation is an infinite clean power generation technology that produces electricity from sunlight. The photovoltaic power generation system includes a solar cell (module) that generates electricity by receiving sunlight, a power control unit that converts the generated direct current into AC, and a balance of system (BOS) such as a battery that stores the generated electricity. . A solar cell is basically a diode composed of pn junctions and is divided into various types according to the material used as the light absorbing layer. Solar cells using silicon as the light absorbing layer are classified into a crystalline substrate type solar cell and a thin film type solar cell. In addition, CdTe and CIS (CuInSe2) compound thin film solar cells, III-V solar cells, dye-sensitized solar cells, and organic solar cells are typical solar cells.

Thin film solar cells are silicon based, CuInSe2 based, and CdTe thin film solar cells, depending on the light absorption layer material used. Advantages of such thin film solar cells are that they can use low cost substrates such as glass or metal plate instead of expensive silicon substrates, It is possible to manufacture solar cells at low cost by minimizing material consumption through thin film deposition inside and outside of the micron. Another advantage is that a large-area module can be manufactured using an in-line process, thereby improving productivity and reducing manufacturing cost. The types of silicon thin film solar cells are variously classified according to the deposition temperature of the thin film, the type of substrate (glass, metal plate, ceramic, silicon substrate, etc.) used and the deposition method. Crystalline silicon thin film solar cells are classified into amorphous and crystalline silicon thin film solar cells according to the crystal characteristics of the light absorption layer, and crystal silicon thin film solar cells are classified according to the crystal size and the thickness of the light absorption layer.

The amorphous silicon (a-Si: H) thin film solar cell has a very low diffusion length of the carrier due to the characteristics of the material itself, and is very low in comparison with a single crystal (or polycrystalline) silicon substrate. The collection efficiency of electron-hole pairs is very low. In general, therefore, the amorphous silicon thin film solar cell has a light absorption layer composed of an intrinsic semiconductor layer to which no impurity is added, and a pin structure in which a p-type semiconductor layer having a high doping concentration is interposed between the n-type semiconductor layer and the p-type semiconductor layer. In this structure, the photoabsorption layer is depleted by the p-layer and the n-layer having a high doping concentration at the top and bottom, and an electric field is generated inside. Therefore, the electron-hole pairs generated from the light absorbing layer by the incident light are collected by the n layer and the p layer by the drift due to the internal electric field instead of diffusion, and the electric current is generated.

In the case of an ideal device, the electric field is generated uniformly inside and the electron-hole pair flow smoothly. However, in real devices, space charge density increases at the pi and ni interfaces due to defects existing in the light absorption layer, and electric field decreases in the light absorption layer. In general, when the solar cell is exposed to light, a characteristic degradation phenomenon (Staebler-Wronski effect) occurs. The characteristics of the solar cell decrease by up to 30% depending on the thickness and physical properties of the light absorption layer. In addition, light-soaking increases the density of dangling bonds inside the light absorbing layer and decreases the internal electric field, thereby further accelerating the recombination of the electron-hole pairs generated by the light, Deterioration occurs.

On the other hand, nanocrystal (nc-Si: H) silicon thin film solar cell is a boundary material between amorphous and monocrystalline silicon. Nanocrystalline silicon, which is often called microcrystalline silicon (μc-Si: H) do. Nanocrystalline silicon has a crystal size of several tens of nanometers to several hundreds of nanometers depending on the deposition method. Amorphous phases are often present at grain boundaries, and most of the carrier recombination occurs at crystal boundaries due to the high bonding density. However, the amorphous silicon thin film solar cell has no deterioration phenomenon. Such a nanocrystalline silicon thin film solar cell is manufactured in the same pin structure as an amorphous silicon thin film solar cell because the grain size of the nanocrystalline silicon is small and contains a large amount of amorphous matrix, Although it is larger than silicon, np structure alone is not sufficient for carrier collection by diffusion.

As for the price of each component of solar power system, it is known that the module occupies the largest portion of total system price with module (60%), peripheral (25%) and installation cost (15%). Module prices, which account for 60% of the total system price, consist of board (40%, silicon), solar cell manufacturing (25%) and module assembly (35%). Considering that the market share of silicon solar cells is very high, the high price of solar power generation systems is due to the high price of solar modules, ie, the high proportion of silicon substrates that make up solar cells. The biggest problem that PV technology is currently sitting on is the high price of the system, which is a major obstacle to the massive supply of photovoltaic power generation. Therefore, energy conversion efficiency is very important for solar cells.

An object of the present invention is to provide an improved high efficiency solar cell capable of achieving a high energy conversion efficiency by preventing the recombination of electron-hole pairs as much as possible by applying a bias voltage to the solar cell so that the charge generated by light is rapidly collected and collected have.

According to an aspect of the present invention, there is provided a high-efficiency solar cell. The high-efficiency solar cell of the present invention comprises: a photovoltaic power generating unit for generating a charge by light absorption; First and second electrodes having different polarities for outputting the photovoltaic power generated by the photovoltaic generation unit to an external load; And a bias electrode for applying an electric field added to the photovoltaic power generator, wherein charges generated in the photovoltaic generator are applied to the first and second electrodes due to an electric field applied by an internal electric field and a bias voltage applied to the bias electrode, The second electrode is collected and flows more quickly toward the second electrode so that recombination of the electron-hole pairs is prevented, and high energy conversion efficiency can be obtained.

In one embodiment, the semiconductor device includes an insulating layer for electrically insulating the bias electrode.

In one embodiment, the photovoltaic power generation part includes a multi-layered light absorbing layer in which an intrinsic amorphous semiconductor film and an intrinsic microcrystalline semiconductor film are alternately repeated.

In one embodiment, the photovoltaic generator includes a heterojunction with intrinsic thin-layer (HIT) structure having an intrinsic thin film.

In one embodiment, the first and second electrodes have an integrated backside contact (IBC) structure.

In one embodiment, the photovoltaic generator includes a multi-layered antireflection film having a porous antireflection film or two or more porous antireflection films stacked.

According to the high efficiency solar cell of the present invention, the charge generated by the bias voltage applied to the bias electrode swiftly collects and collects, so that the recombination of the electron-hole pairs is prevented as much as possible and high energy conversion efficiency can be obtained. The high-efficiency solar cell of the present invention can be applied to various types of amorphous or crystalline silicon thin film type solar cells, and substrate type solar cells using single crystal or polycrystalline silicon substrates. In addition, a high efficiency solar cell can be realized by adding a bias electrode to a compound thin film solar cell of CdTe or CIS (CuInSe2), a III-V solar cell, a dye sensitized solar cell, or an organic solar cell.

For a better understanding of the present invention, a preferred embodiment of the present invention will be described with reference to the accompanying drawings. The embodiments of the present invention may be modified into various forms, and the scope of the present invention should not be construed as being limited to the embodiments described in detail below. The present embodiments are provided to enable those skilled in the art to more fully understand the present invention. Therefore, the shapes and the like of the elements in the drawings can be exaggeratedly expressed to emphasize a clearer description. It should be noted that in the drawings, the same members are denoted by the same reference numerals. Detailed descriptions of well-known functions and constructions which may be unnecessarily obscured by the gist of the present invention are omitted.

1, a general solar cell 10 is mainly composed of first and second electrodes 14 and 16 having different polarities from the photovoltaic generator 12. The photovoltaic power generating unit 12 generates photovoltaic power in response to an optical input, and the generated electromotive force is provided to the external load 18 through the first and second electrodes 14 and 16. [ The external load 18 is, for example, an accumulative charging device for storing the generated photovoltaic power or a power consumption device consuming photovoltaic power. The electron-hole pairs generated in the photovoltaic power generating unit 12 in response to the optical input are mostly connected to the first and second electrodes 14 and 16 by an internal electric field (an electric field generated by the depletion of the p layer and the n layer) And are collected.

However, the electron-hole pairs flowing by the internal electric field are recombined due to various causes in the course of flowing. The higher the recombination ratio, the lower the energy conversion efficiency. In order to overcome such a problem, the high efficiency solar cell of the present invention applies the added electric field by the bias voltage to the solar cell so that the charge generated by the light swiftly flows and collects, thereby preventing the recombination of the electron- The conversion efficiency can be obtained.

2 is a schematic diagram of a high-efficiency solar cell having a bias electrode according to the present invention.

2, a high efficiency solar cell 20 having a bias electrode according to the present invention includes first and second electrodes 24 and 26 having polarities different from those of the photovoltaic power generating unit 22, and a bias electrode 34 ). An insulating film 32 for electrical insulation is provided between the bias electrode 34 and the second electrode 26. The photovoltaic power generating unit 22 generates photovoltaic power in response to the optical input and provides the photovoltaic power to the external load 36. At this time, the bias electrode 34 is driven by receiving a bias voltage from the bias power source 30, and applies a bias voltage to the photovoltaic power generation unit 22. [ The electron-hole pairs generated in the photovoltaic power generating unit 22 are rapidly flown and collected by the electric field formed by the internal electric field and the applied bias voltage, thereby preventing the recombination of the electron-hole pairs to the utmost. The bias power supply 30 basically applies a constant voltage using a DC power supply. Alternatively, the AC voltage can be turned on or the pulse voltage can be applied using an AC power source.

FIG. 3 through FIG. 6 are views showing various embodiments of a high efficiency solar cell.

Referring to FIG. 3, a thin film solar cell 40 having a pin superstrate structure includes a bias electrode 34 as one embodiment of the present invention, thereby realizing a high efficiency solar cell. The thin film solar cell 40 deposits a bias electrode 34 on a substrate 47 and deposits an insulating film 32 thereon. The photovoltaic power generating portion 41 is formed above the insulating film 32. The photovoltaic power generating portion 41 is formed by stacking a light absorbing layer 42 (for example, an intrinsic amorphous silicon film) and a first conductive semiconductor film 43 (for example, p-type) Type semiconductor film 44 (for example, n-type). The first and second conductivity type semiconductor films 43 and 44 may be selected from, for example, a-Si or mc-Si or a-Si / mc-Si. The light absorption layer 42 may be composed of a single film made of an intrinsic amorphous semiconductor film, but it may be composed of a multi-layer structure in which an intrinsic amorphous semiconductor film and an intrinsic microcrystalline semiconductor film are alternately repeated. A transparent conductive film 45 is formed as a first electrode on the first conductive type semiconductor film 43 and a back reflector 46 is formed on the rear surface of the second conductive type semiconductor film 44, And a material having high conductivity and reflectance so as to function as a second electrode, and has a textured structure such as an embossing or a curved shape so as to increase the reflection area.

When light is incident on the light absorbing layer 42 through the transparent electrode 45 and the first conductive type semiconductor film 43, electron-hole pairs are generated, and the first conductive type semiconductor film 43 and the second conductive type semiconductor film 43, (44). At this time, the bias electrode 34 is driven by receiving a voltage from the bias power source 30 and adds an electric field by a bias voltage to an internal electric field generated between the first and second conductive type semiconductor films 43 and 44 . Therefore, the generated electron-hole pairs are rapidly separated and collected by the electric field added by the internal electric field and the bias voltage, thereby preventing the recombination of the electron-hole pairs to the utmost.

Referring to FIG. 4, in another embodiment of the present invention, a thin film solar cell 50 having a nip substrate structure is provided with a bias electrode 34 to realize a high efficiency solar cell. The thin film solar cell 50 having the nip substrate structure has basically the same structure and operating characteristics as the thin film solar cell 40 having the pin super straight structure described above. However, since the thin film solar cell 50 having the nip substrate structure is made incident through the back surface of the substrate 57, the stacking order of the semiconductor films constituting the photovoltaic power generating unit 51 is reversed. That is, a transparent conductive film 55 is laminated on a substrate 57 (the substrate is made of glass, for example, as a light transmitting substrate), and a first conductive type semiconductor film 53 and a light absorbing layer 52 are formed thereon, And the second conductive type semiconductor film 54 are sequentially stacked. Then, the rear reflective film 56 is laminated. The insulating film 32 and the bias electrode 34 are successively laminated.

5, in another embodiment of the present invention, a bias electrode 34 is provided in a crystalline substrate type solar cell 60 having a heterojunction with intrinsic thin-layer (HIT) structure having an intrinsic thin film, Solar cells are implemented. The HIT-structured substrate type solar cell 60 includes an intrinsic semiconductor film 69 (for example, an intrinsic amorphous silicon film) on the surface of the crystal semiconductor substrate 68 (for example, an n-type single crystal silicon substrate) Film and an antireflection film 80 thereon are sequentially formed. In order to increase the light absorption rate, the antireflection film 80 is made of porous silicon having a porous structure on the textured surface of the pyramid structure. The antireflection film 80 may be formed of a single porous antireflection film, but may have a multi-layer structure in which two or more porous antireflection films having the same refractive index or different from each other are overlapped to increase the light absorption rate.

As the back surface of the substrate 68, the photovoltaic generation portion 61 and the semiconductor films for constituting the first and second electrodes are provided adjacent to each other with a gap therebetween. An intrinsic semiconductor film 63 (for example, an intrinsic amorphous silicon film) and a first conductive type semiconductor film 65 (for example, an amorphous silicon film) are sequentially formed on one surface of the substrate 68 in order to constitute the first electrode, a p-type amorphous silicon film) and a conductive film 67 (for example, a transparent conductive film) functioning as a first electrode are laminated. An intrinsic semiconductor film 62 (for example, an intrinsic amorphous silicon film) and a second conductive type semiconductor film 64 (for example, an amorphous silicon film) are sequentially formed on another area on the back surface of the substrate 68, an n-type amorphous silicon film) and a conductive film 66 (for example, a transparent conductive film) functioning as a second electrode are laminated. The conductive films 67 and 66 functioning as the first and second electrodes may be formed of, for example, a transparent conductive oxide film (TCO) such as ITO, SnO2, ZnO, or the like. Although not shown in the drawing, each of the conductive films 67 and 66 may be a metal electrode such as Al or Ag as a collector electrode.

In order to improve the pn junction property, the substrate type solar cell 60 having the HIT structure has a structure in which a substrate 68 made of n-type single crystal silicon and a first conductivity type semiconductor film 65 made of a p-type amorphous silicon film (HIT) structure in which an intrinsic semiconductor film 63 composed of an intrinsic amorphous silicon film is provided. Type semiconductor film 64 composed of an intrinsic semiconductor film 62 composed of an intrinsic amorphous silicon film and an n-type amorphous silicon film on the back surface of a substrate 68 made of n-type single crystal silicon, (Back Surface Field) structure. And an insulating film 32 and a bias electrode 34 are sequentially stacked thereon.

When light is incident on the substrate 68 through the antireflection film 80 and the intrinsic semiconductor layer 69, electron-hole pairs are generated and the first and second conductivity type semiconductor films 65 and 64 And flows separately. At this time, the bias electrode 34 is driven by receiving a voltage from the bias power source 30 and adds an electric field by a bias voltage to an internal electric field generated between the first and second conductive type semiconductor films 65 and 64 . Therefore, the generated electron-hole pairs are rapidly separated and collected by the electric field added by the internal electric field and the bias voltage, thereby preventing the recombination of the electron-hole pairs to the utmost.

6, a bias electrode 34 is provided in a crystalline substrate type solar cell 70 having an integrated backside contact (IBC) structure integrated as another embodiment of the present invention to realize a high efficiency solar cell do. The substrate-type solar cell 70 of the IBC structure is provided with a crystalline semiconductor substrate 78 (for example, an n-type single crystal silicon substrate). A via hole 77 is formed in the substrate 78 so as to extend from one surface to the other surface. An intrinsic semiconductor film 72 (for example, an intrinsic amorphous silicon film) is stacked on one surface and back surface of the substrate 78 and on the side surface of the via hole 77 and the intrinsic semiconductor film 72 A first conductive semiconductor film 74 (for example, a p-type amorphous silicon film) is formed so as to reach the back surface of the substrate 78 through the upper portion of the via hole 77 and the via hole 77. The second conductivity type semiconductor film 73 (for example, an n-type amorphous silicon film) is formed on the back surface of the substrate 78 with an interval around the via hole 77 as a center. An antireflection film 80 is formed on the first conductive type semiconductor film 74 formed on one surface of the substrate 78. The antireflection films 75 and 76 are formed below the second conductive type semiconductor film 73 formed on the back surface of the substrate 78 and below the first conductive type semiconductor film 78 extending to the lower portion of the via hole 77, ). The antireflection film 76 laminated below the first conductive type semiconductor film 74 in the lower portion of the substrate 78 serves as the first electrode and the antireflection film 76 stacked below the second conductive type semiconductor film 73 (75) functions as a second electrode. Although not shown in the figure, each of the antireflection films 76 and 75 may be a metal electrode such as Al or Ag. An insulating film 32 and a bias electrode 34 are sequentially stacked under the antireflection film 75 functioning as the second electrode.

When light is incident on the substrate 78 through the antireflection film 80 and the first conductivity type semiconductor layer 74, electron-hole pairs are generated, and the first conductivity type semiconductor film 74 and the second conductivity type semi- 73). At this time, the bias electrode 34 is driven by receiving a voltage from the bias power source 30 and adds an electric field by a bias voltage to an internal electric field generated between the first and second conductivity type semiconductor films 74 and 73 . Therefore, the generated electron-hole pairs are rapidly separated and collected by the electric field added by the internal electric field and the bias voltage, thereby preventing the recombination of the electron-hole pairs to the utmost.

The above-described high efficiency solar cell of the present invention can be applied to various types of amorphous or crystalline silicon thin film type solar cells, substrate type solar cells using monocrystalline or polycrystalline silicon substrates, as well as the above embodiments. In addition, a high efficiency solar cell can be realized by adding a bias electrode to a compound thin film solar cell of CdTe or CIS (CuInSe2), a III-V solar cell, a dye sensitized solar cell, or an organic solar cell.

The embodiments of the high efficiency solar cell of the present invention described above are merely illustrative and those skilled in the art will appreciate that various modifications and equivalent embodiments are possible without departing from the scope of the present invention. It will be possible. Accordingly, it is to be understood that the present invention is not limited to the above-described embodiments. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims. It is also to be understood that the invention includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.

1 is a schematic diagram of a general solar cell.

Description of the Related Art [0002]

10: solar cell 12: photovoltaic power generation unit

14: first electrode 16: second electrode

18: load 20: solar cell

22: photovoltaic power generation unit 24: first electrode

26: second electrode 30: bias power source

32: insulating film 34: bias electrode

36: load 40: solar cell

41: photovoltaic power generation unit 42: light absorbing layer

43: first conductivity type semiconductor film 44: second conductivity type semiconductor film

45: transparent conductive film 46: rear reflective film

47: substrate 50: solar cell

51: photovoltaic power generation unit 52: light absorbing layer

53: first conductivity type semiconductor film 54: second conductivity type semiconductor film

55: transparent conductive film 56: rear reflective film

57: substrate 60: solar cell

61: photovoltaic power generation unit 62: intrinsic semiconductor film

63: intrinsic semiconductor film 64: second conductivity type semiconductor film

65: first conductivity type semiconductor film 66: conductive film

67: conductive film 68: crystalline semiconductor substrate

69: intrinsic semiconductor film 70: solar cell

71: photovoltaic power generation unit 72: intrinsic semiconductor layer

73: second conductivity type semiconductor film 74: first conductivity type semiconductor film

75: Antireflection film 76: Antireflection film

78: crystal semiconductor substrate 80: antireflection film

Claims

A photovoltaic power generation unit for generating charges by light absorption;

First and second electrodes having different polarities for outputting the photovoltaic power generated by the photovoltaic generation unit to an external load; And

And a bias electrode for applying an electric field added to the photovoltaic power generation unit,

The electric charges generated in the photovoltaic power generating unit are collected and flowed more quickly toward the first and second electrodes due to the electric field added by the internal electric field and the bias voltage applied to the bias electrode so that the recombination of the electron- And a high energy conversion efficiency can be obtained.

The method according to claim 1,

And an insulating layer for electrically insulating the bias electrode.

The method according to claim 1,

The photovoltaic power generation unit

Layer structure in which an intrinsic amorphous semiconductor film and an intrinsic microcrystalline semiconductor film are alternately repeated.

The method according to claim 1,

The photovoltaic power generation unit

And a heterojunction with intrinsic thin-layer (HIT) structure having an intrinsic thin film.

The method according to claim 1,

Wherein the first and second electrodes have an integrated backside contact (IBC) structure.

The method according to claim 1,

Wherein the photovoltaic power generator comprises a multi-layered antireflection film having a porous antireflection film or two or more porous antireflection films superimposed thereon.