KR20150124791A - Semiconductor compound solar cell - Google Patents

Abstract

The present invention relates to a semiconductor compound solar cell. According to the present invention, the semiconductor compound solar cell comprises; a base layer having impurities of a first conductive type; an emitter layer having impurities of a second conductive type opposite to the first conductive type; a high conductive layer located in front of the emitter layer, and having a lower resistance than an emitter portion wherein an impurity doping concentration of the second conductive type is identical to the emitter layer; an electric field formation layer located in front of the high conductive layer, forming the electric field of a positive polarization or a negative polarization on a surface; a first electrode connected to the high conductive layer; and a second electrode connected to the base layer.

Description

[0001] SEMICONDUCTOR COMPOUND SOLAR CELL [0002]

The present invention relates to semiconductor compound solar cells.

A compound semiconductor is a compound that is not a single element such as silicon or germanium but is operated as a semiconductor by combining two or more elements. Various kinds of compound semiconductors are currently being developed and used in various fields. Typically, a compound semiconductor is used for a light emitting device such as a light emitting diode or a laser diode using a photoelectric conversion effect, a solar cell, and a thermoelectric conversion device using a Peltier effect.

Environmentally friendly solar cells that do not require a separate energy source other than natural sunlight are being actively studied as a future alternative energy source. Solar cells are roughly divided into silicon solar cells that use a single element of silicon and semiconductor compound solar cells that use compound semiconductors.

Among them, a semiconductor compound solar cell uses a compound semiconductor for a light absorbing layer (PV) that absorbs sunlight to generate electron-hole pairs. The compound semiconductor includes III-V compound semiconductors such as GaAs, InP, GaAlAs and GaInAs, II-VI group compound semiconductors such as CdTe and ZnS, and I-III-VI group compound semiconductors such as CuInSe2.

An object of the present invention is to provide a semiconductor compound solar cell having improved photoelectric conversion efficiency.

A semiconductor compound solar cell according to the present invention comprises: a base layer containing an impurity of a first conductivity type; An emitter layer containing an impurity of a second conductivity type opposite to the first conductivity type; A high conductivity layer overlying the front surface of the emitter layer, the doping concentration of the impurity of the second conductivity type being equal to the emitter layer and having a lower resistance than the emitter layer; An electroluminescent layer located on the front surface of the highly conductive layer and forming a positive or negative polarization electric field on the surface; A first electrode connected to the high conductivity layer; And a second electrode connected to the base layer.

Here, the energy band gap of the electric field generating layer may be greater than the energy band gap of the emitter layer or the high-conductivity layer, and the energy band gap of the emitter layer and the high-conductivity layer may be equal to each other.

In addition, the electroluminescent layer may have an energy band gap between 5 eV and 7 eV, and the emitter layer and the high conductivity layer may have an energy band gap between 1 eV and 2 eV.

At this time, at least a part of the conduction band of the high-conductivity layer may include an energy level lower than the Fermi energy level formed between the emitter layer and the electro-depositing layer.

In addition, the electric field generating layer may be formed containing a compound containing N, and for example, the electric field generating layer may be formed of any one of AlGaN, AlN, InGaN, InAlGaN, and InN compounds.

Further, the emitter layer and the high-conductivity layer may be formed by including a GaAs compound containing an impurity of the second conductivity type.

Also, the electroluminescent layer may have a thickness between 0.5 nm and 20 nm, and the high conductivity layer may have a thickness between 0.1 nm and 5 nm.

Further, a passivation layer formed of any one of GaAs, GaN, AlGaN, and InGaP compounds may be further formed on the entire surface of the electric field generating layer, and impurities of the first conductivity type may be formed between the base layer and the second electrode, A high concentration doped backside electrical field (BSF) may be further formed.

The sheet resistance value of the emitter layer may be between 50 Ω / cm 2 and 120 Ω / cm 2, and the sheet resistance value of the high conductivity layer may be between 10 Ω / cm 2 and 30 Ω / cm 2.

The semiconductor compound solar cell according to the present invention has a high conductivity layer induced by the electric field forming layer on the front surface of the emitter layer, thereby further improving the efficiency of the solar cell.

FIG. 1 and FIG. 2 illustrate a first embodiment of a semiconductor compound solar cell according to the present invention.
3 shows an example of a band diagram of the emitter layer EL, the high-conductivity layer 160 and the field-forming layer 150 shown in Fig.
4 is a view illustrating a second embodiment in which a passivation layer 170 is further formed on a semiconductor compound solar cell according to the first embodiment of the present invention.
5 is a view for explaining the effect of the compound semiconductor 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 "entirely on another part", it means that it is formed not only on the entire surface (or the front surface) of the other part but also on the edge part.

1 and 2 are views for explaining a first embodiment of a semiconductor compound solar cell according to the present invention. FIG. 3 is a cross-sectional view of an emitter layer EL, a high-conductivity layer 160 and an electro- 150 shown in FIG.

Here, FIG. 1 is a partial perspective view of a first embodiment of a semiconductor compound solar cell according to the present invention, and FIG. 2 is a cross-sectional view along line CS 1 -CS 1 in FIG.

A semiconductor compound solar cell according to the present invention includes a base layer BL, an emitter layer EL, a high conductivity layer 160, an electroforming layer 150, a first electrode 120 and a second electrode 140 For example, a backside electric field (BSF) and a substrate 100 may be further provided between the base layer BL and the second electrode 140, as shown in FIGS.

Here, the rear electric section BSF and the substrate 100 may be omitted. However, the case where it is provided as shown in FIGS. 1 and 2 will be described as an example.

Here, the base layer BL, the emitter layer EL, and the rear electric field portion BSF can function as a light absorbing layer PV that absorbs sunlight to generate electron-hole pairs.

The light absorbing layer PV may be formed on the entire surface of the substrate 100 by an epitaxial growth method using an organic metal chemical vapor deposition (MOCVD) method.

At this time, as the epitaxial growth method, a lattice method of growing the lattice constant of the substrate 100 and the lattice constant of the light absorption layer (PV) formed on the substrate 100 may be used . However, it is not necessarily limited to such a method.

Such a light absorbing layer (PV) may be formed including a III-V semiconductor compound. For example, an InGaP compound containing indium (In), gallium (Ga) and phosphorus (P), or a GaAs compound containing gallium (Ga) and arsenic (As). However, it is not necessarily limited to such a semiconductor compound, but may be formed by including other semiconductor compounds. Hereinafter, a case where a light absorbing layer (PV) is formed by including a GaAs compound as an example will be described as an example.

The light absorbing layer PV may be one as described in the first embodiment, but may be formed in a plurality of different ways.

The base layer BL may be doped with an impurity of the first conductivity type, and may include, for example, a GaAs compound. However, it is not necessarily limited to the GaAs compound, but other kinds of compounds may be used.

The base layer BL can generate electrons and holes, which are carriers, in response to incident light.

The emitter layer EL may be doped with an impurity of the second conductivity type that is opposite the first conductivity type and is disposed over the entire surface of the base layer BL. In addition, it may include the same GaAs compound as the base layer BL. However, it is not necessarily limited to the GaAs compound, and other kinds of compounds having a lattice constant similar to or the same as the base layer BL may be used.

Such an emitter layer EL can collect a small number of carriers in electrons and holes, which are carriers generated in the base layer BL.

Here, the case where the emitter layer EL is located on the front surface of the base layer BL has been shown and described as an example, but it is also possible that the emitter layer EL is located on the rear surface of the base layer BL.

In addition, the rear electric field BSF is located in contact with the rear surface of the base layer BL, and impurities of the first conductive type can be doped at a higher concentration than the base layer BL. For example, the base layer BL Lt; RTI ID = 0.0 > GaAs < / RTI > However, it is not necessarily limited to the GaAs compound, and other kinds of compounds having lattice constants similar to or the same as the emitter layer (EL) may be used.

The impurity of the first conductivity type may be, for example, any one of a p-type impurity and an n-type impurity. The impurity of the p-type may be boron (B), gallium (In), or the like, and the n-type impurity may be an impurity of a pentavalent element such as phosphorus (P), arsenic (As), antimony (Sb), or the like.

In addition, the impurity of the second conductivity type may be an impurity opposite to the first conductivity type. Therefore, when the impurity of the first conductivity type is a p-type impurity, the impurity of the second conductivity type may be an n-type impurity. When the impurity of the first conductivity type is an n-type impurity, May be a p-type impurity.

In the first embodiment, the case where the impurity of the first conductivity type is a p-type impurity and the impurity of the second conductivity type is an n-type impurity will be described as an example.

Therefore, the base layer BL may be formed of a p-GaAs compound doped with a p-type impurity, and the emitter layer EL may be formed of an n-GaAs compound doped with an n-type impurity, The backside electrical field (BSF) may be formed of p + -GaAs.

The electrons generated in the base layer BL can be collected into the first electrode 120 through the emitter layer EL and the electrons generated in the base layer BL can be collected by the rear electric field portion BSF, May be collected into the second electrode 140 through the first electrode 100.

Here, the thickness of the base layer BL may be, for example, between 1 mu m and 3 mu m, and the thickness of the emitter layer EL may be between 0.1 mu m and 1 mu m in a range smaller than the thickness of the base layer BL. .

In addition, the thickness of the rear electric field BSF may be between 0.5 μm and 2 μm, and the energy band gap of the rear electric field BSF may be equal to or lower than the energy band gap of the base layer BL have.

The substrate 100 may be positioned between the light absorbing layer PV and the second electrode 140 and may include a III-V semiconductor compound. For example, gallium (Ga) and arsenic (As) May be formed.

In FIG. 1, the substrate 100 is provided between the light absorbing layer PV and the second electrode 140. However, the substrate 100 may be omitted.

The antireflection film 130 may be disposed on the front surface of the light absorbing layer PV and on a part of the first electrode 120.

Specifically, the antireflection film 130 may be formed on the plurality of finger electrodes 120F, but not on the bus bar electrode 120B, as shown in FIG.

The first electrode 120 may be positioned on the front surface of the light absorbing layer (PV).

2 (a), the first electrode 120 may include a plurality of finger electrodes 120F formed in a first direction and a plurality of finger electrodes 120F in a second direction And a bus bar electrode 120B formed thereon.

The bus bar electrode 120B may be electrically and physically connected to the ends of the plurality of finger electrodes 120F. The plurality of finger electrodes 120F may be spaced apart from each other and may be formed in a stripe shape in a predetermined first direction. So that they can be formed in a stripe shape in the second direction.

Here, each of the plurality of finger electrodes 120F serves to collect carriers, and the bus bar electrode 120B collects all the carriers collected by each of the plurality of finger electrodes 120F and supplies them to an external electric circuit do. For this purpose, a ribbon (not shown) electrically connected to an external electric circuit may be formed on the bus bar electrode 120B.

At this time, the width WF of each finger electrode 120F may be smaller than the width WB of the bus bar electrode 120B. For example, the width WB of the bus bar electrode 120B may be several tens times greater than the width WF of the finger electrode 120F.

The first electrode 120 may include an electrically conductive material. The first electrode 120 may include at least one of gold (Au), germanium (Ge), and nickel (Ni).

1, the second electrode 140 may be positioned entirely on the rear surface of the light absorbing layer PV. When the substrate 100 is positioned on the rear surface of the light absorbing layer PV, Lt; RTI ID = 0.0 > a < / RTI >

On the other hand, the high-conductivity layer 160 is located on the front surface of the emitter layer EL, and the doping concentration of the impurity of the second conductivity type is the same as the emitter layer EL and has a lower resistance than the emitter layer EL. The high-conductivity layer 160 may be formed by an electric field, which is positive or negative, formed by the electric field generating layer 150.

The electroluminescent layer 150 is located on the front surface of the highly conductive layer 160 and forms a positive or negative polarization electric field on the surface. The electroless-formed layer 150 may form a positive or negative electric field to form the high-conductivity layer 160 and perform a surface passivation function.

More specifically, the BSF, the base layer BL and the emitter layer EL are sequentially formed on the entire surface of the substrate 100. The present invention can be applied to the emitter layer 150 EL) formed on the front surface.

At this time, the electro-forming layer 150 may be formed using MOCVD, and the electro-depositing layer 150 may be formed of a compound having a dipole moment.

At this time, the electroluminescence layer 150 may include a compound containing N, and the electroluminescence layer 150 may be formed of any one of AlGaN, AlN, InGaN, InAlGaN, and InN compounds .

For example, when the field-generating layer 150 is formed of AlGaN, a metal-organic chemical vapor deposition (MOCVD) apparatus first forms a nitrogen (N) element layer on the surface of the emitter layer EL on the front surface of the emitter layer EL The nitrogen (N) and the gallium (Ga) are chemically combined and formed into a compound having a dipole moment when the emitter layer (EL) is formed on the surface of the emitter layer (EL) A positive (+) electric field may be formed on the surface of the electric field generating layer 150 which is in contact with the electrode.

Alternatively, if a gallium (Ga) element layer is first formed on the surface of the emitter layer EL and then a nitrogen (N) element layer is formed on the surface of the gallium (Ga) element layer, A negative (-) electric field may be formed on the surface of the electric field generating layer 150.

The positive or negative polarity electric field affects the electric field inside the surface of the emitter layer (EL) contacting the electric field generating layer (150), the energy level of the conduction band of the emitter layer (EL) can be greatly lowered, have.

1 and 2, between the electric field generating layer 150 and the emitter layer EL, a high conductivity layer having the same impurity concentration as the emitter layer EL and having a significantly reduced energy level and sheet resistance of the conduction band, (160) may be formed.

As a result, impurities of the second conductivity type are contained in the same manner as the emitter layer EL, but the highly conductive layer 160, which has a lower resistance than the emitter layer EL due to the electric field of the electric field generating layer 150, Is positioned on the front surface of the emitter layer (EL).

At this time, the doping concentrations of the high-conductivity layer 160 and the emitter layer (EL) may be formed to be between 1018 / cm 3 and 1021 / cm 3. That is, the high-conductivity layer 160 and the emitter layer EL may be formed of the same semiconductor compound, and the impurity doping concentrations may be equal to each other.

Here, the energy band gap Eg1 of the electric field generating layer 150 may be larger than the energy band gap Eg2 of the emitter layer EL or the high conductivity layer 160, as shown in Fig. In addition, the high-conductivity layer 160 and the emitter layer EL have the same doping concentration as the same compound and therefore can have the same energy band gap (Eg2).

For example, the energy band gap Eg1 of the electroluminescence layer 150 may be between 5 eV and 7 eV, and a band off set voltage may be applied to the interface between the electroluminescence layer 150 and the high- , BOS) can be formed. In addition, the energy band gap of the high-conductivity layer 160 and the emitter layer EL can be formed between 1 eV and 2 eV.

In addition, the thickness of the electroluminescent layer 150 may be greater than the thickness of the highly conductive layer 160 induced by the electroluminescent layer 150. For example, the electroluminescent layer 150 may have a thickness between 0.5 nm and 20 nm, and the thickness of the high conductivity layer 160 may be between 0.1 nm and 5 nm.

At least a portion of the conduction band of the high-conductivity layer 160 may have an energy level lower than the Fermi energy level formed between the emitter layer EL and the field-forming layer 150.

Accordingly, the sheet resistance of the high-conductivity layer 160 is in the range of 10 Ω / cm 2 to 30 Ω / cm 2, which is much lower than the sheet resistance value of 50 Ω / cm 2 to 120 Ω / cm 2 of the emitter layer EL due to the influence of the electric field formed by the electric field generating layer 150. Cm < 2 >.

3, electrons are collected at the interface between the high-conductivity layer 160 and the electro-depositing layer 150, which have a relatively low energy level of the conduction band, and the high-conductivity layer 160 And the electroluminescent layer 150 in the horizontal direction, thereby making it easier to move toward the first electrode 120.

The present invention as described above can be applied to the emitter layer EL without increasing the impurity concentration of the emitter layer EL and by forming the high conductivity layer 160 having the same impurity concentration as the emitter layer EL and having a relatively low resistance on the surface of the emitter layer EL The carrier can be more easily moved.

In addition, since the concentration of the impurity is not increased to lower the resistance, the ratio of recombination of carriers by impurities during movement can be remarkably lowered, and since the electric field generating layer 150 performs a passivation function, It may not form a layer.

Therefore, the solar cell according to the present invention can further improve the efficiency of the solar cell, and it is not necessary to form a separate passivation layer, thereby shortening the manufacturing time of the solar cell.

1 and 2, a case where a passivation layer is not formed has been described as an example, but it is also possible to form a passivation layer.

4 is a view illustrating a second embodiment in which a passivation layer 170 is further formed on a semiconductor compound solar cell according to the first embodiment of the present invention.

4, the description of the components other than the passivation layer 170 is the same as that described above with reference to FIGS. 1 to 3, so that a description thereof will be omitted.

As shown in FIG. 4, the semiconductor compound solar cell according to the second embodiment of the present invention may further include a passivation layer 170 between the antireflection film and the electro-depositing layer 150.

The passivation as shown in FIG. 4 may be formed in order to compensate the passivation function when the electro-forming layer 150 is excessively thin so that the electro-forming layer 150 does not perform a sufficient passivation function.

For example, when the electroluminescent layer 150 is formed of an AlN compound, a sufficient positive or negative electric field may be formed even if the thickness is made extremely thin.

For example, when the electroconductive layer 150 is formed of an AlN compound, the electroconductive layer 150 may have a thickness of 0.5 nm to 1 nm. At this time, the passivation function of the electroconductive layer 150 may not be sufficient. Accordingly, a passivation layer 170 may be further formed on the entire surface of the electric field generating layer 150 in order to compensate for this.

Thus, when the passivation layer 170 is formed, the energy band gap of the passivation layer 170 may be smaller than the energy band gap of the field-generating layer 150.

For example, the energy band gap of the passivation layer 170 may be between 1.4 eV and 2.1 eV, but the energy band gap of the electroluminescent layer 150 may be higher than the energy band gap of the passivation layer 170, 5 eV to 7 eV.

For example, when the electroluminescent layer 150 is formed of an AlGaN compound, the energy band gap can be formed to be 5.5 eV, and when it is formed of an AlN compound, it can be formed to be 6.2 eV.

The passivation layer 170 may be formed of any one of GaAs, GaN, AlGaN, and InGaP.

5 is a view for explaining the effect of the compound semiconductor according to the present invention.

5A is a graph for explaining the quantum efficiency (QE) of the comparative example in which the electroluminescent layer 150 and the high-conductivity layer 160 are provided, and FIG. Is a view for explaining a fill factor of a comparative example in which the electric field generating layer 150 and the high conductivity layer 160 are provided and the comparative example.

The numerical values shown in FIG. 5 are only examples for illustrating the effect of the present invention compared with the comparative example, and they are not absolute values and can be changed by other components of the solar cell.

As shown in FIG. 5A, the present invention including the electroluminescence layer 150 and the high-conductivity layer 160 can confirm that the quantum efficiency is further improved in the wavelength band between approximately 300 nm and 500 nm as compared with the comparative example .

More specifically, when the present invention is applied, it can be seen that the short-circuit current Jsc is 28.4 mA, which is more improved than the comparative example of 27.0 mA.

In addition, the fill factor (FF) and the efficiency (Eff) are also improved from 80.1 to 83.8 and the efficiency (Eff) from 23.9% to 25.0% .

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 (13)

A base layer containing an impurity of the first conductivity type;
An emitter layer containing an impurity of a second conductivity type opposite to the first conductivity type;
A highly conductive layer located on the front surface of the emitter layer and having a doping concentration of impurities of the second conductivity type equal to that of the emitter layer and lower than that of the emitter layer;
An electric field generating layer located on the front surface of the high conductivity layer and forming a positive polarization or negative polarization electric field on the surface;
A first electrode coupled to the highly conductive layer; And
A second electrode connected to the base layer;
A semiconductor compound solar cell. The method according to claim 1,
Wherein the energy band gap of the electroluminescence layer is larger than the energy band gap of the emitter layer or the high conductivity layer. 3. The method of claim 2,
Wherein the emitter layer and the high-conductivity layer have the same energy bandgap. 3. The method of claim 2,
Wherein the field-generating layer has an energy band gap between 5 eV and 7 eV,
Wherein the emitter layer and the high conductivity layer have an energy bandgap between 1 eV and 2 eV. The method according to claim 1,
Wherein the electric field generating layer has a thickness between 0.5 nm and 20 nm. The method according to claim 1,
Wherein the electric field generating layer comprises a compound containing N. The method according to claim 1,
Wherein the electroluminescence layer is formed of any one of AlGaN, AlN, InGaN, InAlGaN, and InN compounds. The method according to claim 1,
At least a portion of the conduction band of the high conductivity layer
And an energy level lower than a Fermi energy level formed between the emitter layer and the electroluminescence layer. The method according to claim 1,
Wherein the highly conductive layer has a thickness between 0.1 nm and 5 nm. The method according to claim 1,
Wherein the emitter layer and the highly conductive layer comprise a GaAs compound containing an impurity of a second conductivity type. The method according to claim 1,
And a passivation layer formed on the entire surface of the electroluminescent layer, the passivation layer including any one of GaAs, GaN, AlGaN, and InGaP compounds. The method according to claim 1,
And a rear electric field portion (BSF) doped with impurities of the first conductivity type at a higher concentration than the base layer is further formed between the base layer and the second electrode. The method according to claim 1,
Wherein a surface resistance value of the emitter layer is between 50 Ω / cm 2 and 120 Ω / cm 2, and a surface resistance value of the high conductivity layer is between 10 Ω / cm 2 and 30 Ω / cm 2.

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