KR101404243B1 - Solar cell including phosphors and method for manufacturing the same - Google Patents

Abstract

A solar cell including a phosphor and a method of manufacturing the same are provided. The solar cell has a structure in which a back electrode, a light absorbing layer, a buffer layer, a transparent electrode layer, and a front electrode are sequentially stacked. At least one of the buffer layer and the transparent electrode layer includes a phosphor, A light absorbing layer, a buffer layer, a transparent electrode layer, and a front electrode sequentially formed on the transparent electrode layer and / or the buffer layer, wherein the transparent electrode layer and / or the buffer layer absorb light in a wavelength band And then supplied to the light absorbing layer to increase the amount of light absorption in the visible light wavelength band of about 500 nm to 800 nm to improve the photocurrent density of the solar cell and improve the photoelectric conversion efficiency of the solar cell.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell including a phosphor and a method of manufacturing the same,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solar cell including a phosphor and a method of manufacturing the same, and more particularly, to a thin film solar cell including a transparent electrode layer or a buffer layer with a phosphor and a method of manufacturing the same.

Recently, serious environmental pollution problem and depletion of fossil energy are increasing importance for next generation clean energy development. Among these, solar cells are becoming popular as next generation energy sources that can solve energy problems because they have few pollution, have infinite resources, and can be used semi-permanently.

Solar cells are semiconductor devices that convert light energy directly into electric energy using photovoltaic effect. Such a solar cell can be classified into an inorganic solar cell, a dye-sensitized solar cell, and an organic solar cell including a silicon-based solar cell or a thin film solar cell, cell.

In order to commercialize such a solar cell, it is very important to improve the photoelectric conversion efficiency to convert incident sunlight into electric energy. As part of this, various studies have been conducted to increase the photoelectric conversion efficiency. Of these, studies have been actively made on techniques for increasing photoelectric conversion efficiency by employing a semiconductor thin film having a high light absorption coefficient in a solar cell.

In recent years, thin-film solar cells have achieved high photoelectric conversion efficiencies of about 20.3% and 16%, respectively, in the laboratory scale, and are expected to replace silicon-based solar cells that have been widely used. However, such a thin-film solar cell is less competitive in terms of power generation cost than a silicon-based solar cell, and thus it is necessary to secure a higher photoelectric conversion efficiency.

In general, a thin film solar cell has a multi-layered laminate structure including a front electrode, a transparent electrode layer, a buffer layer, a light absorbing layer, and a rear electrode, from top to bottom.

FIG. 1 is a graph showing the light absorptance according to the wavelength of a constituent material of each layer of a conventional thin-film solar cell.

Referring to FIG. 1, it can be seen that light absorption occurs in the entire region of the visible light wavelength band in the light absorbing layer. On the other hand, it can be confirmed that light absorption occurs in a wavelength band of 400 nm or less in a transparent electrode layer mainly composed of TCO. Also, it can be confirmed that the buffer layer mainly composed of CdS or ZnS has light absorption in a wavelength band of 600 nm or less.

The incident sunlight reaches the light absorbing layer via the transparent electrode layer and the buffer layer, so that there is a problem that loss occurs before the light reaches the light absorbing layer.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a solar cell including a phosphor capable of utilizing light that is lost before reaching the light absorption layer and a method of manufacturing the same.

According to an aspect of the present invention, there is provided a solar cell. The solar cell includes a rear electrode, a light absorbing layer disposed on the rear electrode, a buffer layer disposed on the light absorbing layer, a transparent electrode layer disposed on the buffer layer, and a front electrode disposed on the transparent electrode layer, And the transparent electrode layer include a phosphor.

The phosphor may be an up-conversion phosphor that absorbs light in the infrared wavelength band.

The phosphor may emit light in a wavelength band of 500 nm to 800 nm.

The phosphor _{^{YF 3: (Yb 3 +,}} Er 3 +), NaYF 4: (Yb 3 +, Er 3 +), NaLaF 4: (Yb 3 +, Er 3 +), LaF 4: (Yb 3+, Er ³⁺ ) and BaY ₂ F ₈ : (Yb ^{3 +} , Er ^{3 +} ).

According to an aspect of the present invention, there is provided a method of manufacturing a solar cell. The manufacturing method includes forming a rear electrode on a substrate, forming a light absorbing layer on the rear electrode, forming a buffer layer on the light absorbing layer, forming a transparent electrode layer on the buffer layer, Forming a front electrode on the electrode layer, wherein at least one of the buffer layer and the transparent electrode layer includes a phosphor.

The step of forming the buffer layer including the phosphor may include a step of preparing a mixed solution of a precursor of the material forming the buffer layer and the phosphor and a step of spin coating the mixed solution on the light absorbing layer and then performing heat treatment .

The method may further include adjusting pH and viscosity of the mixed solution between the step of preparing the mixed solution and the step of performing the heat treatment after the spin coating.

The forming of the transparent electrode layer including the phosphor may include forming a mixture by ball-milling the transparent electrode material and the phosphor, drying the mixture to obtain a powder, sintering the powder, And depositing a transparent electrode layer on the buffer layer using the target.

The sintering may use a CIP (Cold Isostatic Pressure) process.

For the deposition of the transparent electrode layer, a sputtering method or a pulsed laser deposition method may be used.

According to the present invention, light having a wavelength band that is lost in the transparent electrode layer and / or the buffer layer is absorbed and then emitted to the light absorbing layer to increase the light absorption amount in the visible light wavelength band of about 500 nm to 800 nm, . As a result, the photoelectric conversion efficiency of the solar cell can be improved.

Furthermore, the photoelectric conversion efficiency can be improved by a simple and easy method of directly incorporating the fluorescent material into the transparent electrode layer and / or the buffer layer without disposing a separate layer containing the fluorescent material.

The technical effects of the present invention are not limited to those mentioned above, and other technical effects not mentioned can be clearly understood by those skilled in the art from the following description.

FIG. 1 is a graph showing the light absorptance according to the wavelength of a constituent material of each layer of a conventional thin-film solar cell.
2 is a cross-sectional view illustrating a solar cell according to an embodiment of the present invention.
3A to 3E are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.
4A and 4B are process flowcharts illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. It is to be understood, however, that the present invention is not limited to the embodiments described herein but may be embodied in other forms and includes all equivalents and alternatives falling within the spirit and scope of the present invention.

When a layer is referred to herein as being "on" another layer or substrate, it may be formed directly on another layer or substrate, or a third layer may be interposed therebetween. In the present specification, directional expressions of the upper side, upper side, upper side, and the like can be understood as meaning lower, lower, lower, and the like according to the standard. That is, the expression of the spatial direction should be understood in the relative direction and should not be construed as limiting in the absolute direction.

In the drawings, the thicknesses of the layers and regions may be exaggerated or omitted for the sake of clarity. Like reference numerals designate like elements throughout the specification.

2 is a cross-sectional view illustrating a solar cell according to an embodiment of the present invention.

Referring to FIG. 2, a rear electrode 20 is disposed on the substrate 10. The substrate 10 is used for supporting and can be removed if necessary. The substrate 10 may be a non-conductive substrate. For example, the substrate 10 may be a glass substrate, a soda-lime glass (SLG) substrate, a ceramic substrate, or the like. However, the present invention is not limited thereto, and a known non-conductive substrate can be used.

The rear electrode 20 serves as an anode for collecting holes generated in a p-n junction to be described later. The rear electrode 20 may be made of a conductive material having a low resistance. The rear electrode 20 may be made of a metal or an alloy thereof. For example, the rear electrode 20 may be formed of at least one selected from Mo, Al, Au, Cu, Pt, Ag, W, Ni, Zn, Ti, Zr, Hf, Cd and Pd. The back electrode 20 may have a thickness of 500 nm to 2000 nm.

A light absorption layer (30) is disposed on the rear electrode (20). The light absorption layer 30 may be a p-type compound semiconductor layer. The light absorbing layer 30 can form a p-n junction at the interface with the transparent electrode layer 50, which will be described later. The p-n junction forms an electron-hole pair in an excited state, that is, an exciton, using light absorbed through the light absorbing layer 40.

For example, the light absorption layer 30 may be formed of CIGS (CuIn _{1 - x} Ga _x Se ₂ , 0 < x < 1) thin film layer. The light absorption layer 30 may have a thickness of 2000 nm to 3000 nm.

A transparent electrode layer 50 is disposed on the light absorbing layer 30. The transparent electrode layer 50 may be an n-type compound semiconductor layer. For example, the transparent electrode layer 50 may be made of ZnO, TiO, SnSO _2, or ITO. The transparent electrode layer 50 may have a thickness of 500 nm to 1000 nm.

At this time, a buffer layer 40 may be further disposed between the light absorption layer 30 and the transparent electrode layer 50. The buffer layer 40 may mitigate the difference between the lattice constant and the energy band gap of the light absorbing layer 30 and the transparent electrode layer 50 to form a good p-n junction.

The buffer layer 40 may include at least one selected from ZnS, CdS, ZnMgO, Zn (OH) ₂ , ZnO, and ZnSe. The buffer layer 40 may have a thickness of 10 nm to 50 nm.

At least one of the buffer layer 40 and the transparent electrode layer 50 may include phosphors 42 and 52 capable of wavelength conversion. The phosphors 42 and 52 may be up-conversion phosphors and / or down-conversion phosphors.

That is, the phosphors 42 and 52 absorb light in the ultraviolet or visible light wavelength band or absorb light in the infrared wavelength band, and then emit light in the visible light wavelength region to the light absorbing layer 30 have. More specifically, the phosphors 42 and 52 absorb light having a wavelength band of less than 500 nm and excite the excited light to emit light having a wavelength band of 500 nm to 800 nm to the light absorbing layer 30. The phosphors 42 and 52 absorb light having a wavelength band of 900 nm to 1200 nm and excite it to emit light having a wavelength band of 500 nm to 800 nm to the light absorbing layer 30.

Accordingly, since the light absorbing layer 30 absorbs the light of the wavelength band of 500 nm to 800 nm which absorbs the most, the amount of the excitons generated in the pn junction increases, and the current density flowing in the cell increases Can be improved.

The phosphors 42 and 52 may be inorganic phosphors. The phosphors 42 and 52 may contain an inorganic material exhibiting luminescence or phosphorescence. It is preferable that the phosphors 42 and 52 have a size of 5 mu m to 30 mu m.

For example, the down-converting phosphor (42, 52) is _{(Y, Tb) 3 Al 5} O 12: Ce 3 +, (Sr, Ba, Ca) 2 Si 5 N 8: Eu 2+, CaAlSiN 3: Eu ^{_{2 +, BaMgAl 10 O 17:}} Eu 2 +, BaMgAl 10 O 17: Eu 2 +, Mn 2 +, Ca-alpha-SiAlON: Eu 2+, Beta-SiAlON: Eu 2 +, (Ca, Sr, Ba) ^{_{2 P 2 O 7: Eu 2}} +, (Ca, Sr, Ba) 2 P 2 O 7: Eu 2+, Mn 2+, (Ca, Sr, Ba) 5 (PO 4) 3Cl: Eu 2 +, Lu ^{_{2 SiO 5: Ce 3 +,}} (Ca, Sr, Ba) 3 SiO 5: Eu 2+, (Ca, Sr, Ba) 2 SiO 4: Eu 2 +, Zn 2 SiO 4: Mn 2 +, BaAl 12 O ^{_{19: Mn 2 +, BaMgAl 14}} O 23: Mn 2 +, SrAl 12 O 19: Mn 2 +, CaAl 12 O 19: Mn 2 +, YBO 3: Tb 3+, LuBO 3: Tb 3 +, Y 2 O ^{_{3: Eu 3 +, Y 2}} SiO 5: Eu 3+, Y 3 Al 5 O 12: Eu 3 +, YBO 3: Eu 3 +, Y 0 .65 Gd 0 .35 BO 3: Eu 3 +, GdBO 3 : Eu ^{3 +,} YVO _4: may be at least one selected from the group consisting of Ce ^{3 +:} Eu ^{3 +} and _{(Y, Gd) 3 (Al} , Ga) 5 O 12.

In addition, each of the up-converting phosphor (42, 52) is _{^{YF 3: (Yb 3 +,}} Er 3 +), NaYF 4: (Yb 3 +, Er 3 +), NaLaF 4: (Yb 3+, Er 3+ ), LaF ₄ : (Yb ^{3 +} , Er ^{3 +} ), and BaY ₂ F ₈ : (Yb ^{3 +} , Er ^{3 +} ). However, the present invention is not limited thereto.

A front electrode 60 is disposed on the transparent electrode layer 50. The front electrode 60 serves as a cathode for collecting electrons generated at the p-n junction. The front electrode 60 may be made of a conductive material. The front electrode 60 may be made of a metal having a small work function or an alloy thereof. For example, the front electrode 60 may be formed of at least one selected from Al, Au, Cu, Pt, Ag, W, Ni, Zn, Ti, Zr, Hf, Cd and Pd.

3A to 3E are cross-sectional views illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

4A and 4B are process flowcharts illustrating a method of manufacturing a solar cell according to an embodiment of the present invention.

Referring to FIG. 3A, a back electrode 20 is formed on a substrate 10. For example, the rear electrode 20 may be formed by sputtering, evaporation, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or the like. As shown in FIG. The rear electrode 20 may have a thickness of 500 nm to 2000 nm.

The substrate 10 may be a non-conductive substrate. For example, the substrate 10 may be a glass substrate, a soda-lime glass (SLG) substrate, a ceramic substrate, or the like.

The rear electrode 20 may be formed using a metal or an alloy thereof. For example, the rear electrode 20 may be formed of at least one metal selected from Mo, Al, Au, Cu, Pt, Ag, W, Ni, Zn, Ti, Zr, Hf, Cd and Pd.

Referring to FIG. 3B, a light absorbing layer 30 is formed on the rear electrode 20. For example, the light absorbing layer 30 may be formed by a sputtering method, a vacuum deposition method, or a rapid thermal annealing method. The light absorption layer 30 is formed of CIGS (CuIn _{1 - x} Ga _x Se ₂ , 0 < x < 1) thin film layer. The light absorption layer 30 may have a thickness of 2000 nm to 3000 nm.

Referring to FIGS. 3C and 4A, a buffer layer 40 is formed on the light absorbing layer 30. The buffer layer 40 may be formed using at least one selected from ZnS, CdS, ZnMgO, Zn (OH) ₂ , ZnO, and ZnSe. The buffer layer 40 may include a phosphor 42. The phosphor 42 may be an inorganic phosphor. The phosphor 42 may contain an inorganic material exhibiting light emission or phosphorescence. The buffer layer 40 may have a thickness of 10 nm to 50 nm.

For example, the buffer layer 40 including the phosphor 42 may be formed by a sol-gel method or a spin coating method. More specifically, a mixed solution containing the precursor of the buffer layer 40 and the phosphor 42 may be prepared (S100).

The precursor may be a salt containing Cd or Zn. The phosphor may be a down conversion phosphor and / or an up conversion manganese phosphor. At this time, the pH of the mixed solution can be adjusted to 9 to 12 by adding ammonia or the like. The viscosity of the mixed solution may be controlled by adding TEA, hydrazine hydrate, Na ₂ EDTA or tri-citrate (S200). Thereafter, the mixed solution is spin-coated on the light absorbing layer 30 (S300), and the buffer layer 40 including the phosphor 42 is formed by heat treatment (S400) on the hot plate. For example, the spin coating may be performed at 500 to 300 rpm for 10 to 30 seconds. The heat treatment may be performed at 200 to 300 ° C for 1 to 10 minutes.

Referring to FIGS. 3D and 4B, a transparent electrode layer 50 is formed on the buffer layer 40. The transparent electrode layer 50 may be formed of ZnO, TiO ₂ , SnSO ₂ Or ITO. The transparent electrode layer 50 may include a phosphor 52. The phosphor 52 may be an inorganic phosphor. The phosphor 52 may contain an inorganic material that exhibits luminescence or phosphorescence. The transparent electrode layer 50 may be formed to have a thickness of 500 nm to 1000 nm.

For example, the transparent electrode layer 50 including the phosphor 52 may be formed using a ball-milling method and a deposition method. More specifically, first, a transparent electrode material, a fluorescent material, a zirconia ball and a solvent are put into a certain container, sealed, and then ball-milling is performed for mixing them (S100). Thereafter, the mixture may be dried and pulverized to form a powder (S200). Thereafter, the powder can be sintered (S300). For example, the powder may be sintered using a CIP (Cold Isostatic Pressure) process. At this time, the sintering may be performed at 800 to 1200 ° C for 2 to 5 hours using a mold of a certain type. Thereafter, the transparent electrode layer 50 can be formed by depositing a thin film on the buffer layer 40 using the sintered mold as a target (S400). At this time, the deposition can be performed using a sputtering method or a pulsed laser deposition (PLD) method.

Referring to FIG. 3E, a front electrode 60 is formed on the transparent electrode layer 50. For example, the front electrode 60 may be formed by sputtering, evaporation, metal organic chemical vapor deposition (MOCVD), molecular beam epitaxy (MBE), or the like. As shown in FIG.

At this time, the front electrode 60 may be formed using a metal having a small work function or an alloy thereof. At least one of Al, Au, Cu, Pt, Ag, W, Ni, Zn, Ti, Zr, Hf, Cd and Pd may be selected as a single metal or alloy .

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, but, on the contrary, This is possible.

10: substrate 20: rear electrode
30: light absorbing layer 40: buffer layer
50: window layer 42, 52: phosphor layer
60: front electrode

Claims (10)

Rear electrode;
A light absorbing layer disposed on the rear electrode;
A buffer layer disposed on the light absorbing layer;
A transparent electrode layer disposed on the buffer layer; And
And a front electrode disposed on the transparent electrode layer,
Wherein at least one of the buffer layer and the transparent electrode layer comprises a phosphor. The method according to claim 1,
Wherein the phosphor is an up-conversion phosphor that absorbs light in an infrared wavelength band. The method according to claim 1,
Wherein the phosphor emits light in a wavelength band of 500 nm to 800 nm. The method according to claim 1,
The phosphor _{^{YF 3: (Yb 3 +,}} Er 3 +), NaYF 4: (Yb 3 +, Er 3 +), NaLaF 4: (Yb 3 +, Er 3 +), LaF 4: (Yb 3+, Er ³⁺ ) and BaY ₂ F ₈ : (Yb ^{3 +} , Er ^{3 +} ). Forming a back electrode on the substrate;
Forming a light absorption layer on the rear electrode;
Forming a buffer layer on the light absorbing layer;
Forming a transparent electrode layer on the buffer layer; And
And forming a front electrode on the transparent electrode layer,
Wherein at least one of the buffer layer and the transparent electrode layer includes a phosphor. 6. The method of claim 5,
The step of forming the buffer layer containing the phosphor may include:
Preparing a mixed solution of a precursor of a material forming the buffer layer and a phosphor; And
And spin-coating the mixed solution on the light absorbing layer, followed by heat treatment. The method according to claim 6,
Further comprising the step of adjusting the pH and viscosity of the mixed solution between the step of preparing the mixed solution and the step of performing the heat treatment after the spin coating. 6. The method of claim 5,
The forming of the transparent electrode layer including the phosphor may include:
Ball-milling the transparent electrode material and the phosphor to form a mixture;
Drying and pulverizing the mixture to obtain a powder;
Sintering the powder to produce a target; And
And depositing a transparent electrode layer on the buffer layer using the target. 9. The method of claim 8,
Wherein the sintering is performed using a CIP (Cold Isostatic Pressure) process. 9. The method of claim 8,
Wherein the transparent electrode layer is deposited using a sputtering method or a pulse laser deposition method.

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