JP3172368B2 - Photovoltaic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photovoltaic device for converting light energy such as sunlight into electric energy.

[0002]

2. Description of the Related Art Conventionally, various types of photovoltaic devices for converting light energy such as sunlight into electric energy have been known. One of such photovoltaic devices is shown in FIG. As shown in FIG. 1, a light-transmitting conductive film 2 such as TCO is provided on an insulating light-transmitting substrate 1 such as glass, and a p-type (or n-type) is formed on the light-transmitting conductive film 2. A semiconductor layer 3a (or 3c) made of a semiconductor of the type, a photovoltaic layer 3b made of an i-type semiconductor, and a semiconductor layer 3c (or 3a) made of an n-type (or p-type) semiconductor Is provided, and the photoelectric conversion layer 3 is further provided.
Back electrode 4 made of a highly reflective metal such as Ag or Al
Was known.

In such a photovoltaic device, light is guided from the light-transmitting substrate 1 side to the photoelectric conversion layer 3 through the light-transmitting conductive film 2, and the carrier is generated in the photovoltaic layer 3b. Are generated to perform photoelectric conversion.

In recent years, in a photovoltaic device as described above, as shown in FIG.
The interface between the light-transmitting conductive film 2 and the photoelectric conversion layer 3 is textured so that the light-transmitting conductive film 2 is guided to the photoelectric conversion layer 3 through the light-transmitting conductive film 2. In addition to suppressing the reflection of light at the interface with, the light guided to the photoelectric conversion layer 3 is scattered to increase the optical path length of light passing through the photoelectric conversion layer 3. Was.

Here, when the interface between the light-transmitting conductive film 2 and the photoelectric conversion layer 3 is made uneven as in the photovoltaic device shown in FIG. 2, the light-transmitting conductive film 2 and the photoelectric conversion layer 3 The optical path length of light passing through the photovoltaic layer 3b of the photoelectric conversion layer 3 is longer than that of the photovoltaic device of FIG. The current has increased.

However, when the interface at which the light-transmitting conductive film 2 and the photoelectric conversion layer 3 are in contact with each other is made uneven, the fill factor (FF) is reduced as compared with a case where the interface is flat. However, there has been a problem that the conversion efficiency cannot be sufficiently improved.

[0007]

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems in a photovoltaic device, and an uneven interface between a light transmitting conductive film and a photoelectric conversion layer is provided. It is an object of the present invention to provide a photovoltaic device having high conversion efficiency without a decrease in fill factor even when the photovoltaic device is formed.

Here, the present inventors have found that the fill factor is reduced when the interface where the translucent conductive film 2 and the photoelectric conversion layer 3 come into contact with each other is made uneven as in the photovoltaic device shown in FIG. The cause was studied.

As a result, when the interface at which the translucent conductive film 2 and the photoelectric conversion layer 3 are in contact with each other is made uneven, as described above, the internal electric field in the photoelectric conversion layer 3 becomes non-uniform in the plane direction, As shown in FIG. 3, in the portion of the photoelectric conversion layer 3 that is in contact with the concave portion 2 a of the light-transmitting conductive film 2, which is a portion where light absorption is large, the density of the electric flux lines indicated by the broken line is higher than the light-transmitting property. The distance between the equipotential lines indicated by the alternate long and short dash line gradually increases toward the light-transmitting conductive film 2, and the distance between the equipotential lines indicated by the dashed line increases.
It was found that the internal electric field in the portion of the photoelectric conversion layer 3 in contact with the light-transmitting conductive film 2 side was weakened. Then, a large amount of carrier recombination occurs in the portion of the photoelectric conversion layer 3 in which the internal electric field has been weakened, thereby decreasing the fill factor in the photovoltaic device and hindering improvement in conversion efficiency. I understood.

Therefore, the present inventors conducted further research based on the above research results, and found that the photoelectric conversion layer 3 had an uneven interface at the interface between the transparent conductive film 2 and the photoelectric conversion layer 3. In the case where the internal electric field in the conversion layer 3 becomes non-uniform in the plane direction of the layer surface, this is corrected, and a means for suppressing the decrease of the fill factor in the photovoltaic device and improving the conversion efficiency has been developed. Thus, the present invention has been completed.

[0011]

According to the present invention, in order to solve the above-mentioned problems, a photovoltaic device in which a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film are in contact with each other. In the above, when the internal electric field in the photoelectric conversion layer is non-uniform in the plane direction of the layer surface, the photovoltaic layer in the portion of the photoelectric conversion layer where the internal electric field is weakened contains a ferroelectric substance.

Further, in the present invention, the interface between the photoelectric conversion layer having the photovoltaic layer provided therein and the light-transmitting conductive film is formed in an uneven shape, and the photoelectric conversion layer is in contact with the concave portion of the light-transmitting conductive film. In a photovoltaic device in which the internal electric field in the convex portion of the conversion layer is weakened, a ferroelectric substance is formed in a portion of the photoelectric conversion layer on the light-transmitting conductive film side in a portion of the photoelectric conversion layer in contact with the concave portion of the light-transmitting conductive film. It was made to contain.

Here, as the ferroelectric, for example, BaTiO ₃ , PbTiO ₃ , LiNbO ₃ , Li
A substance having a relative dielectric constant of 20 or more, such as TaO ₃ or SbSI, is used.

[0014]

According to the present invention, in a photovoltaic device in which a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film come into contact with each other, an internal electric field in the photoelectric conversion layer does not extend in a plane direction of the layer surface. In the case of uniformity, since the ferroelectric substance was included in the photovoltaic layer in the part of the photoelectric conversion layer where the internal electric field was weakened, the lines of electric force in the part of the photoelectric conversion layer where the internal electric field was weakened were , The density of the lines of electric force in this portion increases. This increases the electric field strength in the portion of the photoelectric conversion layer where the internal electric field is weakened, reduces the difference in the internal electric field from other portions, makes the internal electric field uniform, and weakens the internal electric field as in the related art. The recombination of carriers at the distorted portion is reduced, and a decrease in the fill factor in the photovoltaic device is suppressed, thereby improving the conversion efficiency.

The interface between the photoelectric conversion layer having the photovoltaic layer provided therein and the light-transmitting conductive film is formed in an uneven shape, and the portion of the photoelectric conversion layer in contact with the concave portion of the light-transmitting conductive film is formed. In a photovoltaic device in which the internal electric field is weakened, when a ferroelectric substance is contained in a portion of the photovoltaic layer on the light-transmitting conductive film side in a portion of the photoelectric conversion layer in contact with the concave portion of the light-transmitting conductive film, As described above, the electric field strength in the portion of the photoelectric conversion layer where the internal electric field is weakened increases, the difference in the internal electric field from the other portions decreases, the internal electric field becomes uniform, and the recombination of carriers in this portion decreases. As a result, a decrease in the fill factor is suppressed, and the conversion efficiency is further improved along with an increase in the short-circuit current.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a photovoltaic device according to an embodiment of the present invention will be specifically described with reference to the accompanying drawings, and the photovoltaic device of this embodiment will be superior to a conventional photovoltaic device. Make it clear.

In the photovoltaic device according to this embodiment, as shown in FIG. 4, on an insulating translucent substrate 1 made of glass or the like, a textured SnO ₂ having an uneven surface is used. A light-transmitting conductive film 2 is formed, and a photoelectric conversion layer 3 that performs photoelectric conversion on the light-transmitting conductive film 2
p-type semiconductor layer 3a made of p-type amorphous silicon carbide, photovoltaic layer 3b made of i-type amorphous silicon, and n-type semiconductor made of n-type amorphous silicon And a back electrode 4 made of a highly reflective metal such as Ag or Al on the photoelectric conversion layer 3.
Was provided.

Here, in the photovoltaic device of this embodiment, in the photoelectric conversion layer 3 in contact with the concave portion 2a of the translucent conductive film 2, titanium is used as a ferroelectric material 5 at an appropriate position of the photovoltaic layer 3b. Barium acid (BaTiO ₃ ) particles 5
Was contained.

In manufacturing the photovoltaic device as described above, in this embodiment, first, FIG.
As shown in FIG. 2A, thermal CVD is performed on the light-transmitting substrate 1.
The light-transmitting conductive film 2 was textured by a method or the like to form an uneven surface.

Next, as shown in FIG. 5B, the boron-doped p-type semiconductor layer 3 is formed on the light transmitting conductive film 2 formed as described above by a plasma CVD method or the like.
a was formed under the film forming conditions shown in Table 1 below. The thickness of the p-type semiconductor layer 3a was set to be in the range of 50 to 200 °.

Thereafter, on the p-type semiconductor layer 3a, by the plasma CVD method or the like, under the film forming conditions shown in Table 1 below, FIG.
As shown in (C), the photovoltaic layer 3b was formed so that its thickness was about 500 ° at first.

The photovoltaic layer 3 formed as described above
On the surface of b, sputtering of BaTiO ₃ was performed under the sputtering conditions shown in Table 2 below, and FIG.
As shown in FIG. ₃ , BaTiO ₃ is formed on the surface of the photovoltaic layer 3b.
After feeding particles 5, thus by applying ultrasonic waves to that BaTiO ₃ particles 5 is supplied, the BaTiO ₃ particles 5 supplied is distributed on the surface of the photovoltaic layer 3b, FIG. 5 (E As shown in FIG.
In the photovoltaic layer 3b.

In a state where the BaTiO ₃ particles 5 are collected in the recesses of the photovoltaic layer 3b, a photovoltaic layer 3b is further formed on the photovoltaic layer 3b under the same conditions. After the total film thickness is about 1000 to 10000 °, the n-type semiconductor layer 3c is formed on the photovoltaic layer 3b under the film forming conditions shown in Table 1 below to have a film thickness of 100 to 10,000 °.
The photovoltaic device of this embodiment shown in FIG. 4 was manufactured by forming the back electrode 4 on the n-type semiconductor layer 3c.

[0024]

[Table 1]

[0025]

[Table 2]

Here, as in the photovoltaic device of this embodiment, in the portion of the photoelectric conversion layer 3 which is in contact with the concave portion 2a of the translucent conductive film 2, the photovoltaic layer 3 inside the photoelectric conversion layer 3
When the ferroelectric material 5 composed of BaTiO ₃ particles 5 is contained in the portion b of the light-transmitting conductive film 2 side, as shown in FIG. Is attracted to the ferroelectric material 5 contained in the transparent conductive film 2, and the density of the lines of electric force in this portion is increased. The interval between the equipotential lines in the portion on the side of the film 2 was narrowed, and the internal electric field in that portion was increased to be uniform with other portions.

As a result, in the photovoltaic device of this embodiment, the interface between the light-transmitting conductive film 2 and the photoelectric conversion layer 3 is textured to have an uneven shape, and light passes through the light-transmitting conductive film 2. When guided to the photoelectric conversion layer 3, the reflection of light at the interface between the translucent conductive film 2 and the photoelectric conversion layer 3 is suppressed, and the light guided to the photoelectric conversion layer 3 is scattered to perform photoelectric conversion. Even when the optical path length of the light passing through the layer 3 is increased, the internal electric field in the portion of the photoelectric conversion layer 3 that is in contact with the concave portion of the translucent conductive film 2 is weakened as in the related art. As a result, the photovoltaic device with good conversion efficiency can be obtained with less reduction of the fill factor due to recombination of carriers.

Next, as described above, the interface between the light-transmitting conductive film 2 and the photoelectric conversion layer 3 is formed in an uneven shape, and the light in the photoelectric conversion layer 3 contacting the concave portion 2a of the light-transmitting conductive film 2 is formed. The photovoltaic device of this embodiment in which the power generation layer 3b contains the ferroelectric material 5 and the concave portion 2 of the translucent conductive film 2 as shown in FIG.
a photovoltaic device of Comparative Example 1 in which the photovoltaic layer 3b in the photoelectric conversion layer 3 in contact with a did not contain the ferroelectric substance 5,
As shown in FIG. 1, in the photovoltaic device of Comparative Example 2 in which the interface at which the translucent conductive film 2 and the photoelectric conversion layer 3 are in contact with each other is flat, the photovoltaic layer 3b and the p-type semiconductor layer 3a are respectively It was investigated how the electric field intensity in the photovoltaic layer 3b changes as it proceeds from the contacting interface to the inside of the photovoltaic layer 3b, and the results are shown in FIG. In the figure,
The changes in the respective electric field intensities are shown by the solid line in the above-described embodiment, by the one-dot chain line in the comparative example 1, and by the broken line in the comparative example 2.

As a result, the translucent conductive film 2 and the photoelectric conversion layer 3
In the photovoltaic device of Comparative Example 2 in which the interface in contact with was flat, the electric field intensity in the photovoltaic layer 3b hardly changed even when the distance from the interface in contact with the p-type semiconductor layer 3a changed. However, in the photovoltaic device of Comparative Example 1 in which the interface at which the translucent conductive film 2 and the photoelectric conversion layer 3 are in contact has an uneven shape, the electric field intensity is within a range of about 2000 ° from the interface of the p-type semiconductor layer 3a. It was significantly weaker. On the other hand, in the photovoltaic device of this embodiment, Comparative Example 1
Transparent conductive film 2 and photoelectric conversion layer 3 as in the photovoltaic device of FIG.
Despite the fact that the interface in contact with is formed in an uneven shape, the decrease in the electric field strength in the range of about 2000 ° from the interface of the p-type semiconductor layer 3a is considerably reduced, and the light-transmitting conductive film 2 and the photoelectric conversion layer 3 The contacting interface became flat and approached the photovoltaic device of Comparative Example 2.

In the case of the photovoltaic device of Comparative Example 2, p
Although the electric field intensity in the photovoltaic layer 3b hardly changed even when the distance from the interface in contact with the type semiconductor layer 3a changed, the photovoltaic device of Comparative Example 2 The effect when the interface in contact with the photoelectric conversion layer 3 is formed in an uneven shape, for example, when light is guided to the photoelectric conversion layer 3 through the light-transmitting conductive film 2, the light-transmitting conductive film 2 and the photoelectric conversion layer 3 The amount of light guided to the photoelectric conversion layer 3 is increased by suppressing the reflection of light at the interface with the light, or the light guided to the photoelectric conversion layer 3 is scattered and passes through the inside of the photoelectric conversion layer 3. Since there is no effect such as an increase in the short-circuit current due to an increase in the optical path length, light is not used effectively and the conversion efficiency is deteriorated as compared with the embodiment.

Next, as described above, the photovoltaic layer 3b in the photoelectric conversion layer 3 in contact with the concave portion 2a of the translucent conductive film 2 has B
When the aTiO ₃ particles 5 are contained, the photovoltaic layer 3
The average particle diameter of the BaTiO ₃ particles 5 contained in b was changed. And B contained in the photovoltaic layer 3b.
The relationship between the average particle size of the aTiO ₃ particles 5 and the open-circuit voltage (Voc), short-circuit current (Isc), fill factor (FF), and conversion efficiency (η) in the photovoltaic device was determined, and the results were plotted. 8 is shown.

As a result, when BaTiO ₃ particles 5 having an average particle diameter in the range of 10 to 80 ° are contained, the fill factor (FF) and the conversion efficiency (η) in the photovoltaic device are improved. And BaTiO ₃ particles 5 having a particle size in this range.
Was preferred.

In the portion of the photoelectric conversion layer 3 which is in contact with the concave portion 2a of the light transmitting conductive film 2 as described above, the photovoltaic layer 3
Upon incorporating the BaTiO ₃ particles 5 in b, then change the position of incorporating the BaTiO ₃ particles 5, obtains the relationship between the conversion efficiency at a distance and the photovoltaic device from the surface in contact with the p-type semiconductor layer 3a, The result is shown in FIG. Here, the total thickness of the photovoltaic layer 3b is set to about 500
0 °.

[0034] BaTiO ₃ result, the distance from the surface in contact with the p-type semiconductor layer 3a is in the range of 1000~1200Å
When the particles 5 were contained, the conversion efficiency in the photovoltaic device was improved by about 5%.

In the photovoltaic device of this embodiment, the BaTiO ₃ particles 5 are contained at a position of about 500 ° from the surface in contact with the p-type semiconductor layer 3a based on such a result. _The position at which the _three particles 5 are contained can be freely adjusted by changing the thickness of the photovoltaic layer 3b to be deposited first. For example, the position of the interface where the translucent conductive film 2 and the photoelectric conversion layer 3 are in contact with each other can be adjusted. The unevenness and the thickness of the entire photovoltaic layer 3b change, and the photoelectric conversion layer 3
When the position where the internal electric field is weak in the inside changes, the thickness of the first photovoltaic layer 3b is changed to change the position where the BaTiO ₃ particles 5 are contained.

In this embodiment, the ferroelectric 5
As an example, only an example in which the BaTiO ₃ particles 5 are used is shown, but instead of the BaTiO ₃ particles 5, PbTiO ₃ is used.
Almost the same effects can be obtained when a transparent ferroelectric material 5 having a relative dielectric constant of 20 or more such as ₃ , LiNbO ₃ , LiTaO ₃ , SbSI or the like is used.

In this embodiment, a p-type semiconductor layer 3a, a photovoltaic layer 3b, and an n-type semiconductor layer 3c are sequentially formed as a photoelectric conversion layer 3 on a light-transmitting conductive film 2 having an uneven shape. Although the structure having the laminated structure is shown, the light-transmitting conductive film 2
May have a structure in which the photoelectric conversion layer 3 formed thereon is stacked in the order of the n-type semiconductor layer 3c, the photovoltaic layer 3b, and the p-type semiconductor layer 3a. In this case, the n-type The ferroelectric 5 as described above is contained in the portion on the semiconductor layer 3c side.

Further, in the photovoltaic device of this embodiment, the interface at which the photoelectric conversion layer 3 and the translucent conductive film 2 are joined is formed in an uneven shape, and the internal electric field in the photoelectric conversion layer 3 is reduced by the surface of the layer. Although only an example in which the non-uniformity is obtained in the plane direction of the layer is shown, even if the internal electric field in the photoelectric conversion layer 3 becomes non-uniform in the plane direction of the layer surface due to other causes, As described above, the ferroelectric material 5 is contained in the photovoltaic layer 3b of the photoelectric conversion layer 3 having a weak internal electric field, thereby making the internal electric field in the photoelectric conversion layer 3 uniform to some extent, and The fill factor in the device can be improved.

[0039]

As described in detail above, according to the present invention, in a photovoltaic device in which a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film are in contact with each other, When the electric field is non-uniform in the plane direction of the layer surface, the photovoltaic layer in the portion of the photoelectric conversion layer where the internal electric field has weakened contains a ferroelectric substance, so that the electric field strength in the portion where the internal electric field is weak increases. In the photovoltaic device, the reduction of the fill factor is suppressed, and the photovoltaic device with high conversion efficiency is suppressed. A power device was obtained.

Further, according to the present invention, there is provided a photovoltaic device in which an interface at which a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film come into contact with each other is formed in an uneven shape. Since the ferroelectric material is contained in the portion of the photoelectric conversion layer on the light-transmitting conductive film side in the portion of the photoelectric conversion layer in contact with the concave portion of the film, the internal electric field in contact with the concave portion of the light-transmitting conductive film is reduced by this ferroelectric material. In the portion of the weak photoelectric conversion layer on the side of the light-transmitting conductive film, the electric field strength increases, the difference in the internal electric field from the other portions is reduced, and the internal electric field is made uniform. Recombination is less likely.

As a result, the interface where the light-transmitting conductive film and the photoelectric conversion layer are in contact with each other is made uneven, and when light is guided to the photoelectric conversion layer through the light-transmitting conductive film, the light-transmitting conductive film and the photoelectric conversion layer Suppresses the reflection of light at the interface with and increases the amount of light guided to the photoelectric conversion layer, or scatters the light guided to the photoelectric conversion layer and scatters the light to pass through the photoelectric conversion layer. In the photovoltaic device in which the short-circuit current is increased by increasing the length, the reduction of the fill factor can be suppressed, and the conversion efficiency can be further improved.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view of a conventional photovoltaic device in which a contact interface between a light-transmitting conductive film and a photoelectric conversion layer is flattened.

FIG. 2 is a schematic cross-sectional view of a conventional photovoltaic device in which an interface between a light-transmitting conductive film and a photoelectric conversion layer has an uneven shape.

FIG. 3 is a schematic explanatory view showing states of electric lines of force and equipotential lines in a photoelectric conversion layer of the photovoltaic device shown in FIG.

FIG. 4 is a schematic sectional view showing a structure of a photovoltaic device according to one embodiment of the present invention.

FIG. 5 is a schematic explanatory view showing a step of manufacturing the photovoltaic device of the embodiment.

FIG. 6 shows a photovoltaic device according to the embodiment, in which BaTiO 3 is used.
FIG. 3 is a schematic explanatory view showing states of electric lines of force and equipotential lines in a photoelectric conversion layer containing _three particles.

FIG. 7 is a diagram showing a state of an electric field strength inside each photovoltaic layer in each of the photovoltaic devices of the example and comparative examples 1 and 2.

FIG. 8 is a diagram showing the relationship between the average particle size of BaTiO ₃ particles contained in the photoelectric conversion layer and the open voltage, short circuit current, fill factor, and conversion efficiency in the photovoltaic device.

FIG. 9 is a diagram showing the relationship between the position where BaTiO ₃ particles are contained in the photoelectric conversion layer and the conversion efficiency of the photovoltaic device.

[Description of Signs] 1 translucent substrate 2 translucent conductive film 2a concave portion of translucent conductive film 3 photoelectric conversion layer 3a p-type semiconductor layer 3b photovoltaic layer 3c n-type semiconductor layer 5 ferroelectric (BaTiO ₃ particles) )

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01L 31/04-31/078

Claims (3)

(57) [Claims] In a photovoltaic device in which a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film are in contact with each other, an internal electric field in the photoelectric conversion layer is non-uniform in a plane direction of the layer surface. A photovoltaic device, wherein the photovoltaic layer at the portion of the photoelectric conversion layer where the internal electric field has weakened contains a ferroelectric substance. 2. A photovoltaic device in which an interface between a photoelectric conversion layer having a photovoltaic layer provided therein and a light-transmitting conductive film has an uneven shape, wherein the photoelectric contacting a concave portion of the light-transmitting conductive film. A photovoltaic device, wherein a ferroelectric substance is contained in a portion of the photovoltaic layer on the light-transmitting conductive film side in the portion of the conversion layer. 3. The photovoltaic device according to claim 1, wherein said ferroelectric material is BaTiO ₃ , PbT.
A photovoltaic device using any one of iO ₃ , LiNbO ₃ , LiTaO ₃ , and SbSI.