JP4441377B2 - Photoelectric conversion device and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photoelectric conversion device and a method for manufacturing the same, and more particularly to a technology for improving the efficiency of a photoelectric conversion device.

Oil and other fossil fuels used as electric energy resources are concerned about the future supply shortage due to the problem of residual resources, and there is a problem of carbon dioxide emissions that cause global warming. Solar cells are attracting attention as an alternative energy source for fuel.
The solar cell generally uses a pn junction made of a semiconductor for a photoelectric conversion layer that converts light energy into electric energy, and silicon is most widely used as a raw material. Currently, the most popular solar cells using silicon are those using bulk crystals such as single crystal silicon and polycrystalline silicon. In recent years, the production of these bulk crystal solar cells has greatly increased. Module prices are falling and the spread of photovoltaic power generation systems is expanding rapidly. However, since bulk crystal solar cells use a silicon substrate with a thickness of several hundred μm, the silicon raw material costs account for a large portion of the solar cell price, making it difficult to significantly reduce costs. Currently.

  In addition, solar cells are known as clean energy that does not emit carbon dioxide and other emissions during power generation. However, when solar cells are manufactured, energy input is required, and the energy input involves carbon dioxide emission. Reducing carbon dioxide emissions during production is also an important issue in the spread of solar cells as a countermeasure against global warming. However, since both the single crystal silicon substrate and the polycrystalline silicon substrate used in the bulk crystal solar cell require a high temperature of 1500 ° C. or higher for melting silicon during production, a method utilizing the bulk crystal growth of silicon Therefore, it is considered difficult to significantly reduce carbon dioxide emissions during production in the future.

  On the other hand, as a next-generation solar cell technology for reducing the cost by greatly reducing the amount of silicon used for the bulk crystal solar cell, a thin-film silicon solar cell has been developed. The thin film silicon solar cell is manufactured by depositing a silicon thin film having a thickness of several μm on a glass substrate, a stainless steel substrate or the like by a plasma CVD method or the like. Therefore, not only the amount of silicon used can be reduced to about one-hundredth of the bulk crystal solar cell, but also a solar cell with a large area can be produced by a single film formation. In recent years, attention has been increasing. In addition, since the thin film silicon semiconductor layer can be manufactured by a low temperature process of 300 ° C. or lower, the input energy at the time of manufacture, and hence the carbon dioxide emission amount can be greatly reduced as compared with the bulk crystal solar cell.

The photoelectric conversion layer of the thin film silicon solar cell is generally formed of a semiconductor thin film such as hydrogenated amorphous silicon or hydrogenated microcrystalline silicon. In this specification, the term “amorphous” is used as a synonym for “amorphous” generally used in this field. Further, the term “microcrystal” includes not only a state substantially consisting of only a crystalline phase but also a state in which a crystalline phase and an amorphous phase are mixed, as generally used in the field. For example, in the Raman scattering spectrum, if even a slight peak near 520 cm ⁻¹ attributed to a silicon-silicon bond in crystalline silicon is detected, it is considered “microcrystalline silicon”. The term “microcrystalline silicon” is used in the same sense. In other words, “microcrystalline silicon” contains silicon atoms as a crystalline silicon phase and is not only in a state consisting essentially of a crystalline silicon phase, but also in a state where a crystalline silicon phase and an amorphous phase are mixed. Including. The hydrogenated microcrystalline silicon solar cell is superior to a hydrogenated amorphous silicon solar cell in that photodegradation does not occur, and has attracted attention in recent years as a thin film silicon solar cell capable of achieving higher efficiency.

  As a structure of a general thin film silicon solar cell, there are two types, a super straight type and a substrate type. The super straight type structure is a structure in which a transparent conductive layer, a photoelectric conversion layer, and an electrode layer are laminated in this order on a translucent substrate, and the translucent substrate side serves as a light incident surface. On the other hand, the substrate type structure is a structure in which an electrode layer, a photoelectric conversion layer, a transparent conductive layer, and a grid electrode are laminated on a substrate in this order, and the grid electrode side serves as a light incident surface. In any structure, the photoelectric conversion layer includes a semiconductor layer exhibiting p conductivity type (hereinafter referred to as a p layer), an intrinsic semiconductor layer (hereinafter referred to as i layer), and a semiconductor layer exhibiting an n conductivity type (hereinafter referred to as p layer). It is often provided with a pin junction composed of n layers).

  As described above, the thin-film silicon solar cell has the advantage of being able to reduce the cost by simultaneously forming a large area and can reduce carbon dioxide emissions during production, but in reality it is bulky. It has not yet reached a market expansion phase like crystalline solar cells. The main factor is considered to be the low photoelectric conversion efficiency compared with the bulk crystal solar cell. In other words, the lower the photoelectric conversion efficiency of the solar cell, the more the number of solar cell modules to cover the same power generation capacity, and the installation cost also increases. Therefore, low-cost thin-film silicon solar cells are used. Nevertheless, there is a problem that the system price is not necessarily lower than that of a bulk crystal solar cell.

  Therefore, high efficiency is an important issue for the full-scale spread of thin-film silicon solar cells. As one means, a wide band gap of a semiconductor layer (hereinafter referred to as a window layer) on the light incident surface side of the solar cell. The technology has been studied energetically. The thin-film silicon solar cell can increase the short-circuit current density by reducing the light absorption loss in the window layer and increase the open-circuit voltage by increasing the diffusion potential by widening the band gap of the window layer. Can be increased. When the amorphous silicon i layer is used as the active layer, the carrier mobility of holes is lower than that of electrons, so that the p-type semiconductor layer is used as a window layer on the light incident side to improve carrier collection efficiency. It is common to make it. Even when a microcrystalline silicon i layer is used as an active layer, this is often followed.

  As a conventional technique related to the wide band gap of the window layer as described above, there is a thin film photoelectric conversion device described in Japanese Patent Laid-Open No. 2002-16271 (Patent Document 1). The technology includes a p-type conductive p-type semiconductor layer, a substantially intrinsic i-type semiconductor layer, and a photoelectric conversion layer including at least one pin junction structure formed by laminating an n-type conductive n-type semiconductor layer; In a thin film photoelectric conversion device having a conductive and light transmissive first electrode provided on the light incident side of the photoelectric conversion layer and a second electrode provided on a surface facing the first electrode, The i-type semiconductor layer constituting the junction is made of microcrystalline silicon or microcrystalline silicon germanium, and at least one of the p-type semiconductor layer and the n-type semiconductor layer in contact therewith is a mixed crystal of microcrystalline silicon carbide and microcrystalline silicon. Consists of. According to this thin film photoelectric conversion device, the light absorption of the p-type semiconductor layer and the n-type semiconductor layer is reduced, and the band gap of the interface is increased, so that interface recombination is reduced and high photoelectric conversion efficiency is obtained. It is said. Further, in Patent Document 1, it is preferable that the carbon content of the mixed crystal of the microcrystalline silicon carbide and the microcrystalline silicon is in the range of 10 to 30% in terms of atomic ratio, and the atomic ratio is 10%. If it is less than 30%, the light absorption rate is not sufficiently lowered, and there is no effect of mixing microcrystalline silicon carbide. Conversely, if the amount of carbon exceeds 30%, the resistance increases, and a sufficient saturation current density cannot be obtained. It is stated that it is not.

  As described above, Patent Document 1 is a technology that achieves high efficiency by increasing the p-type wide band gap, but the same effect can be expected by increasing the wide band gap of the n-type semiconductor layer. As an example, there is a thin film solar cell described in, for example, JP-A-2002-9313 (Patent Document 2). The technology is a pin junction thin film solar cell in which a plurality of semiconductor layers are stacked, and has a pin structure mainly composed of amorphous silicon, and the band gap of the n layer of the pin structure is wider than that of the i layer, It is a thin film solar cell characterized by containing a trace amount of n-type impurities in the i layer. According to this thin-film solar cell, when the internal electric field at the i / n interface is weakened by a small amount of n-type impurities contained in the i layer, the n layer having a larger band gap than the i layer causes A band offset occurs, which acts in a direction to block carrier despreading, and carrier loss at the interface is greatly reduced, resulting in improved efficiency. Examples of suitable materials for the n layer having a large band gap include amorphous silicon oxide, amorphous silicon carbide, amorphous silicon oxycarbide, amorphous silicon nitride, and amorphous silicon oxynitride.

  However, when the i layer does not contain any n-type impurities, and the internal electric field at the i / n interface is not weakened, the wide band gap is formed by using the wide band gap material for the n layer. There is a problem that the photoelectric conversion efficiency improvement effect equivalent to the case has not been obtained. Japanese Patent Laid-Open No. 2004-228561 discloses a technology that indicates that the high-efficiency technology obtained with the p-type semiconductor layer can also be applied to the n-type semiconductor layer. However, this technology has the following problems. To do.

  In the technique of Patent Document 1, when carbon is used as an additive element for wide band gap, a large amount of carbon of 10 atomic% or more is required to be contained in the silicon film. Accompanied by an increase in silicon dangling hands. In other words, since the impurity is added at a high concentration of 10 atomic% or more, the density of silicon dangling bonds formed in the film increases as compared with the case where the impurity concentration is low. Therefore, since the defect density of the semiconductor layer increases and the conductivity decreases, the form factor of the solar cell may decrease. Further, as the concentration of carbon, which is an impurity element, in the film increases, the activation efficiency when the conductivity determining element doped in the p-type semiconductor layer or the n-type semiconductor layer is activated as a dopant in the film decreases. It is known that the carrier concentration is lowered by adding impurities at a high concentration. Furthermore, the smaller the impurity element concentration in the film, the easier it is to crystallize, and there is a possibility that the ratio of the amorphous phase in the p-type semiconductor layer or n-type semiconductor layer will increase under the high concentration conditions. In the technique of Patent Document 1, the carbon-containing gas used in the production of the microcrystalline silicon carbide is not preferable because it ultimately causes an increase in carbon dioxide emission. More specifically, in the above plasma CVD method, most of the carbon-containing gas introduced into the CVD apparatus is exhausted without being decomposed in the plasma, so that the carbon that is not taken into the film of the photoelectric conversion layer is excluded. It will be processed via harmful devices. Therefore, the use of the carbon-containing gas causes an increase in carbon dioxide emission during the production of solar cells.

JP 2002-16271 A JP 2002-9313 A

  The present invention provides a photoelectric conversion device in which the open-circuit voltage and the short-circuit current are increased and the photoelectric conversion efficiency is improved without containing an impurity element at a high concentration in the n-type conductive semiconductor layer, and the photoelectric conversion device It is an object of the present invention to suppress carbon dioxide emissions during production by providing a conversion device.

The present inventors have found that at least one layer of the n-type semiconductor layer in the pin-type photoelectric conversion layer contains a nitrogen atom, so that a higher photoelectric conversion efficiency can be obtained than when no nitrogen atom is contained. The headline, the present invention has been completed.
Thus, according to the present invention, the p-type semiconductor layer, the i-type semiconductor layer, and one or more pin-type photoelectric conversion layers configured by laminating at least a silicon atom-containing n-type semiconductor layer, and At least one n-type semiconductor layer in the one or more pin-type photoelectric conversion layers contains nitrogen atoms, and the concentration of nitrogen atoms contained in the n-type semiconductor layer containing nitrogen atoms is 0.001. There is provided a photoelectric conversion device having a crystal silicon phase of -10 atomic% .
The present invention according to another aspect includes forming p-type semiconductor layer via a conductive film on a substrate, a photoelectric conversion layer with i-type semiconductor layer and n-type semiconductor layer of one or more, the In the step of forming the n-type semiconductor layer of the photoelectric conversion layer, nitrogen gas having a nitrogen atom concentration of 0.001 to 10 atom% with respect to the silicon atom concentration is obtained using a source gas containing silicon atoms, an n-type conductive element, and nitrogen atoms. Provided is a method for manufacturing a photoelectric conversion device that includes an atom and an n-type semiconductor layer that includes a nitrogen atom so as to have a crystalline silicon phase .

According to the photoelectric conversion device of the present invention, in particular, the n-type semiconductor layer containing nitrogen atoms has an open-circuit voltage and a short-circuit current when the concentration of nitrogen atoms contained therein is 0.01 to 10 atomic%. Can be increased, the photoelectric conversion efficiency can be improved, and high efficiency of the thin-film silicon solar cell can be realized.
In addition, according to the method for manufacturing a photoelectric conversion device of the present invention, the above highly efficient photoelectric conversion device can be manufactured while significantly reducing the input energy as compared with a bulk crystal solar cell. Carbon emissions can be greatly reduced.

The photoelectric conversion device of the present invention has one or more pin-type photoelectric conversion layers configured by laminating a p- type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer containing at least silicon atoms, and At least one n-type semiconductor layer in the one or more pin-type photoelectric conversion layers contains a nitrogen atom .

In the photoelectric conversion device of the structure, the nitrogen concentration of the n-type semiconductor layer is preferably 0.001 to 10 atomic%, more preferably 0.01 to 10 atomic%. Thereby, in addition to the increase in the open circuit voltage, the effect of increasing the short-circuit current of the photoelectric conversion device due to the increase in the transmittance of the n-type semiconductor layer can be obtained, so that the photoelectric conversion efficiency is further improved.
Further, in the photoelectric conversion device, it is further preferable that the n-type semiconductor layer containing crystalline silicon phase. In other words, the n-type semiconductor layer may be a microcrystalline silicon layer containing nitrogen atoms. By making the n-type semiconductor layer a microcrystalline silicon layer, the conductivity of the n-type semiconductor layer is improved as compared to the amorphous silicon layer, so that the series resistance can be reduced, and the form factor of the photoelectric conversion device is increased. As a result, high photoelectric conversion efficiency can be obtained. Furthermore, by setting the crystallization rate of the n-type semiconductor layer to 3 or more, since the bond with the i-type semiconductor layer is well formed, high photoelectric conversion efficiency is obtained, which is more preferable.

Further, in the photoelectric conversion device, it is further preferable that the i-type semiconductor layer containing silicon atoms as the crystalline silicon phase. In other words, the i-type semiconductor layer may be a microcrystalline silicon layer. As a result, not only an i-type semiconductor layer without photodegradation can be obtained, but also an n-type semiconductor layer made of a microcrystalline silicon layer and an i-type semiconductor layer form a good junction, whereby the i / n layer interface is regenerated. Since the coupling suppression effect is enhanced, the form factor of the photoelectric conversion device is increased, and higher photoelectric conversion efficiency can be obtained.

Further, in the photoelectric conversion device, p-type semiconductor layer further preferably contains impurities such as carbon atom, a nitrogen atom. By including these impurities, the photoelectric conversion efficiency is improved. The reasons are as follows: (1) the band gap of the p-type semiconductor layer widens and the diffusion potential increases; (2) the interface passivation at the grain boundaries due to the addition of impurities and the p-type semiconductor layer / i-type semiconductor layer interface passivation. It is conceivable that interface recombination is reduced due to the effect. Further, when the impurity concentration is low, band gap discontinuity or mismatch does not occur so much between the p-type semiconductor layer and the i-type semiconductor layer. Therefore, an interface layer or the like is provided between the two layers. Since it is not necessary, a photoelectric conversion device that is simple, inexpensive, and has high photoelectric conversion efficiency can be obtained.

Note that the photoelectric conversion device may have a super straight type structure in which light is incident from the substrate side, or may have a substrate type structure in which light is incident from the opposite side of the substrate, that is, the grid electrode side. Further, it may be a super straight type stacked photoelectric conversion device provided with two pin type photoelectric conversion layers or a substrate type stacked photoelectric conversion device. In the stacked photoelectric conversion device, three or more photoelectric conversion layers may be provided. Further, in the stacked photoelectric conversion device, a light-transmitting conductive film may be provided between the photoelectric conversion layers.

  Hereinafter, embodiments of the photoelectric conversion device of the present invention will be described in detail with reference to the drawings, but the present invention is not limited thereto.

[Embodiment 1]
As shown in FIG. 1, the photoelectric conversion device 100 of Embodiment 1 is a super straight type, and is configured by laminating a photoelectric conversion layer 10, a transparent conductive layer 15, and an electrode 16 in this order on a substrate 11. ing.

<Description of substrate>
The substrate 11 is manufactured by depositing a transparent conductive layer 11b on a translucent substrate 11a. As the translucent substrate 11a, a glass plate, a translucent resin plate having heat resistance such as polyimide and polyvinyl, and a laminate of them are preferably used. However, the entire photoelectric conversion device has high light transmissivity. If it can support structurally, it will not specifically limit. Further, the surface thereof may be a metal film, a transparent conductive film, an insulating film, or the like. However, when the photoelectric conversion device is applied to a substrate type structure, an opaque substrate such as stainless steel may be used instead of the transparent substrate 11a.

  The transparent conductive layer 11b is made of a transparent conductive material. For example, a single layer or a plurality of laminated layers of transparent conductive films such as ITO, tin oxide, and zinc oxide can be used. Since the transparent conductive layer 11b plays a role as an electrode, it is preferable that the electrical conductivity is high, and a layer whose electrical conductivity is improved by adding a small amount of impurities can also be used. Examples of the method for forming the transparent conductive layer 11b include known methods such as a sputtering method, a CVD method, an electron beam vapor deposition method, a sol-gel method, a spray method, and an electrodeposition method. Moreover, it is preferable that the uneven | corrugated shape is formed in the surface of the transparent conductive layer 11b. The unevenness can scatter and refract incident light incident from the translucent substrate 11a side to extend the optical path length, so that the light confinement effect in the photoelectric conversion layer 10 is enhanced and an improvement in the short circuit current can be expected. As a method for forming irregularities on the surface of the transparent conductive layer 11b, after the transparent conductive layer 11b is once deposited on the translucent substrate 11a, the irregularities are formed by mechanical processing such as etching or sand blasting, Using a method using surface irregularities formed by crystal growth of a film material when forming a transparent conductive layer, a method utilizing regular surface irregularities formed because the crystal growth surface is oriented, etc. Also good. In the present embodiment, a substrate using unevenness formed during crystal growth of a film material is obtained by depositing a tin oxide layer on a white plate glass by a CVD method (Asahi Glass Co., Ltd., trade name Asahi-U). Was used as the substrate 11. Furthermore, it is more preferable that a zinc oxide layer is deposited on the substrate 11 by a sputtering method, so that the tin oxide layer can be prevented from being damaged by plasma when the photoelectric conversion layer 10 is formed later. .

<Description of photoelectric conversion layer>
The main material of the photoelectric conversion layer 10 is silicon, and amorphous silicon, microcrystalline silicon, or the like is particularly preferably used. Here, in the present invention, the terms “amorphous silicon” and “microcrystalline silicon” include “hydrogenated amorphous silicon” and “hydrogenated microcrystalline silicon”, which are generally used in this field, respectively. In the photoelectric conversion layer 10 of the present embodiment, a p-type semiconductor layer 12, an i-type semiconductor layer 13, and an n-type semiconductor layer 14 are deposited in this order from the substrate 11 side to form a pin junction structure. The film thickness of each type of semiconductor layer is not particularly limited, but the p-type semiconductor layer 12 is 5 to 50 nm, the i-type semiconductor layer 13 is 100 to 5000 nm, and the n-type semiconductor layer 14 is 5 to 100 nm. Preferably, the p-type semiconductor layer 12 is 10 to 30 nm, and the i-type semiconductor layer 13 is 200 to 200 nm.
4000 nm, n-type semiconductor layer 14 is 10-30 nm.

  The p-type semiconductor layer 12 is a silicon layer doped with a p-type conductivity determining element. As the p-type conductivity determining element, impurity atoms such as boron, aluminum, and gallium can be used. The p-type semiconductor layer 12 may be an amorphous silicon layer or a microcrystalline silicon layer. Here, the microcrystalline silicon layer means a semiconductor layer made of a mixed phase of a fine crystalline silicon phase and an amorphous silicon phase when formed at a low temperature using a non-equilibrium process such as a plasma CVD method. When the p-type semiconductor layer 12 includes a crystalline silicon phase, high conductivity can be obtained and the series resistance of the photoelectric conversion layer can be reduced, so that the form factor can be increased and high photoelectric conversion efficiency can be obtained. The type semiconductor layer 12 preferably contains a crystalline silicon phase. Further, when the p-type semiconductor layer 12 includes a crystalline silicon phase, the p-type semiconductor layer 12 is excellent as a base layer for crystallization of the i-type semiconductor layer 13. Is easy to grow, and a high-quality i-type semiconductor layer 13 with a high crystallization rate is obtained, which is preferable because the short-circuit current density increases and high photoelectric conversion efficiency can be obtained.

  The p-type semiconductor layer 12 further preferably contains carbon atoms or nitrogen atoms as impurities. By containing the impurities, the photoelectric conversion efficiency is improved. The reasons are as follows: (1) the band gap of the p-type semiconductor layer widens and the diffusion potential increases; (2) the interface passivation at the grain boundaries due to the addition of impurities and the p-type semiconductor layer / i-type semiconductor layer interface passivation. It is conceivable that interface recombination is reduced due to the effect. In addition, when the impurity concentration is low, band gap discontinuity or mismatch does not occur between the p-type semiconductor layer 12 and the i-type semiconductor layer 13, so an interface layer or the like is present between the two layers. Therefore, it is more preferable because a photoelectric conversion device that is simple, inexpensive, and has high photoelectric conversion efficiency can be obtained.

  In addition, when the p-type semiconductor layer 12 contains a carbon atom as an impurity, the silicon carbide crystal phase is substantially not included. This state is confirmed, for example, by confirming that a peak attributed to a silicon-carbon bond constituting the silicon carbide crystal is not substantially detected when a Raman scattering spectrum of the microcrystalline silicon containing the carbon atom is observed. Can do. This state may also be confirmed by substantially not detecting a diffraction peak attributed to the silicon carbide crystal structure in the X-ray diffraction method.

  Furthermore, the p-type semiconductor layer 12 may contain impurities of both carbon atoms and nitrogen atoms.

The i-type semiconductor layer 13 is a microcrystalline silicon layer to which no impurity is added. However, a small amount of impurity elements may be included as long as it is a substantially intrinsic semiconductor. In this case, as the i-type semiconductor layer 13, amorphous silicon may be used instead of microcrystalline silicon, but microcrystalline silicon is used in that high photoelectric conversion efficiency can be obtained because no photodegradation occurs. Is more preferable .

  The n-type semiconductor layer 14 is a silicon layer doped with an n-type conductivity determining element. As the n-type conductivity determining element, impurity atoms such as phosphorus, nitrogen, and oxygen can be used. The n-type semiconductor layer 14 contains nitrogen atoms at a concentration of 0.001 to 10 atomic%, and an open circuit voltage is increased and high photoelectric conversion efficiency is obtained as compared with an n-type semiconductor layer not containing nitrogen atoms. . The reason why the open-circuit voltage increases by containing nitrogen atoms is as follows: (1) the band gap of the n-type semiconductor layer widens and the diffusion potential increases; (2) interface passivation and i of the grain boundary due to the addition of nitrogen; It is conceivable that interface recombination is reduced by the effect of / n layer interface passivation.

  Further, the n-type semiconductor layer 14 has a nitrogen concentration of 0.01 to 10 atomic%, so that in addition to the improvement of the open circuit voltage, the light transmittance is improved, so that the short-circuit current density is increased and the photoelectric conversion efficiency is increased. Is further improved. Further, as described above, when nitrogen atoms are added as an impurity element to the n-type semiconductor layer 14, the open circuit voltage is improved at a low impurity concentration of 10 atomic% or less compared to the addition of carbon atoms as in the prior art. An effect can be obtained. Therefore, in addition to the above effects (1) and (2), as an advantage of a low impurity concentration, (3) an increase in defect density due to impurity addition, and an amorphous phase in the n-type semiconductor layer 14 due to impurity addition An effect that can suppress the increase in the ratio can be expected. Further, (4) it is possible to suppress a decrease in the activation efficiency of the n-type conductivity determining element due to the addition of impurities, and (5) since carbon atoms are not used, there is an advantage that the amount of carbon dioxide emission during production does not increase.

As the n-type semiconductor layer 14, a layer in which nitrogen atoms are added to amorphous silicon can be used. However, if crystalline silicon is included, higher conductivity can be obtained and the series resistance of the photoelectric conversion layer can be reduced. It preferably contains silicon. That is, it is preferable to use a layer in which nitrogen atoms are added to microcrystalline silicon because the shape factor increases and higher photoelectric conversion efficiency can be obtained. Further, the n-type semiconductor layer 14 preferably has a crystallization ratio of 3 or more. Here, the crystallization rate is the peak of crystalline silicon at 520 cm ⁻¹ attributed to a silicon-silicon bond with respect to the peak height Ia of amorphous silicon at 480 cm ⁻¹ in the Raman scattering spectrum of a single n-type semiconductor layer. The ratio of the height Ic, that is, Ic / Ia is defined. This is not a value representing the absolute value of the crystal volume fraction, but since Ic / Ia well reflects the crystal volume fraction, it is generally used as an index indicating the proportion of crystallized components in the film in this field. used. If the crystallization rate of the n-type semiconductor layer 14 is 3 or more, a good junction with the i-type semiconductor layer 13 is formed, and the above-mentioned i / n interface recombination suppression with the i-type semiconductor layer 13 is suppressed. Since an effect is easy to be acquired and high photoelectric conversion efficiency is obtained, it is more preferable.

A typical method for forming the photoelectric conversion layer 10 is a CVD method. Examples of the CVD method include atmospheric pressure CVD, low pressure CVD, plasma CVD, thermal CVD, hot wire CVD, and MOCVD method. In this embodiment, the plasma CVD method is used. The silicon-containing gas used when forming the photoelectric conversion layer 10 by the plasma CVD method is not particularly limited as long as it contains silicon atoms such as SiH ₄ and Si ₂ H _6, but generally SiH ₄ is used. There are many cases. As the diluent gas used together with the silicon-containing gas, H ₂ , Ar, He, or the like can be used, but H ₂ is often used when forming amorphous silicon and microcrystalline silicon. Further, when forming the p-type semiconductor layer and the n-type semiconductor layer, a doping gas is used together with the silicon-containing gas and the dilution gas.
The doping gas is not particularly limited as long as it contains a target type conductivity determining element, but generally B ₂ H ₆ is determined when the p-type conductivity determining element is boron, and n-type conductivity determination is performed. When the element is phosphorus, PH ₃ is often used.

When the photoelectric conversion layer 10 is formed by the plasma CVD method, the ratio of the amorphous phase to the crystalline phase is controlled by appropriately controlling the film forming parameters such as the substrate temperature, pressure, gas flow rate, and input power to the plasma. It is possible to control. The nitrogen-containing gas used when forming the n-type semiconductor layer 14 is not particularly limited as long as it contains nitrogen atoms such as N ₂ and NH ₃ , but N ₂ is used in the present embodiment. In particular, N ₂ is preferable because it can be produced at low cost by separation from air, such as a cryogenic gas separation method, and it is a stable substance and does not require a detoxification treatment.

<Description of electrode and transparent conductive layer>
The electrode 16 only needs to have at least one conductive layer, and the higher the light reflectivity, the higher the conductivity. As materials that satisfy these requirements, metallic materials such as silver, aluminum, titanium, and palladium with high visible light reflectivity and alloys thereof are used. CVD, sputtering, vacuum deposition, electron beam deposition, spraying, screen printing It is formed on the photoelectric conversion layer 10 by a method or the like. Since the electrode 16 reflects the light that has not been absorbed by the photoelectric conversion layer 10 and returns it to the photoelectric conversion layer 10 again, it contributes to the improvement of the photoelectric conversion efficiency. Furthermore, when the transparent conductive layer 15 is formed between the photoelectric conversion layer 10 and the electrode 16, the effect of improving the light confinement and the light reflectance with respect to incident light can be obtained, and the photoelectric of the elements contained in the electrode 16 can be obtained. Diffusion to the conversion layer 10 can be suppressed. The transparent conductive layer 15 can be formed by the same material and manufacturing method as the transparent conductive layer 11b. However, when the present invention is applied to a substrate type structure, the electrode 16 preferably has a grid shape such as a comb shape that does not cover the surface uniformly.

  With the above configuration, a super straight type (or substrate type) photoelectric conversion device 100 having a large open circuit voltage, short circuit current density, and high form factor and high photoelectric conversion efficiency can be obtained.

[Embodiment 2]
Next, as a second embodiment different from the above, a superstrate stacked photoelectric conversion device 200 having two photoelectric conversion layers will be described with reference to FIG. In FIG. 2, the same components as those in the first embodiment shown in FIG.
The super straight type stacked photoelectric conversion device 200 is configured by laminating a first photoelectric conversion layer 10, a second photoelectric conversion layer 20, a transparent conductive layer 15 and an electrode 16 in this order on a substrate 11. Yes. Among these components, the substrate 11, the transparent conductive layer 15, and the electrode 16 can be the same as the super straight photoelectric conversion device 100 described above, and the function of each component is the same as that of the super straight photoelectric conversion device 100. Since it is the same, description is abbreviate | omitted.

  Since the first photoelectric conversion layer 10 is located on the light incident side, only the light transmitted through the first photoelectric conversion layer 10 is incident on the second photoelectric conversion layer 20. For this reason, advantages of the stacked structure include that the incident light spectrum region can be divided and received so that light can be used effectively and a high open-circuit voltage can be obtained. In order to enhance the above effect, if the first photoelectric conversion layer 10 on the light incident side is laminated so that the band gap is larger than the band gap of the second photoelectric conversion layer 20, short wavelength light among the incident light is reduced. Since the long wavelength light is mainly absorbed by the second photoelectric conversion layer 20 mainly in the first photoelectric conversion layer 10, each wavelength region can be used effectively.

  The first and second photoelectric conversion layers 10 and 20 may be stacked so that the bonding directions of the pins are the same, and the light incident side may be a p-type semiconductor layer. The same applies when there are three or more layers. In FIG. 2, 22 is a p-type semiconductor layer, 23 is an i-type semiconductor layer, and 24 is an n-type semiconductor layer. The thickness of each layer of the first and second photoelectric conversion layers 10 and 20 is not particularly limited, but in the first photoelectric conversion layer 10, the p-type semiconductor layer 12 is 5 to 50 nm, and the i-type semiconductor layer 13. Of the n-type semiconductor layer 14 is preferably in the range of 5 to 50 nm, preferably the p-type semiconductor layer 12 is 10 to 30 nm, the i-type semiconductor layer 13 is 200 to 400 nm, and the n-type semiconductor layer 14 is In the second photoelectric conversion layer 20, the p-type semiconductor layer 22 is 5 to 50 nm, the i-type semiconductor layer 23 is 1000 to 5000 nm, and the n-type semiconductor layer 24 is 5 to 100 nm, more preferably p. The type semiconductor layer 22 is 10 to 30 nm, the i type semiconductor layer 23 is 2000 to 4000 nm, and the n type semiconductor layer 24 is 10 to 30 nm.

  Moreover, the intermediate | middle layer may be formed between the 1st and 2nd photoelectric converting layers 10 and 20 (between each photoelectric converting layer in three layers or more). In this case, the intermediate layer is preferably a transparent conductive film. By providing the intermediate layer, a part of the light incident on the intermediate layer from the first photoelectric conversion layer 10 is reflected by the intermediate layer, and the remaining light passes through the intermediate layer and passes through the second photoelectric conversion layer. Therefore, the amount of light incident on each photoelectric conversion layer can be controlled. Thereby, the photocurrent values of the photoelectric conversion layers 10 and 20 are equalized, and the photogenerated carriers generated in the photoelectric conversion layers 10 and 20 can contribute to the short-circuit current of the stacked photoelectric conversion device almost without waste. As a result, the short circuit current of the stacked photoelectric conversion device can be increased and the photoelectric conversion efficiency can be improved.

  In this photoelectric conversion device 200, 0.001 to 10 in the n-type semiconductor layer in at least one of the first and second photoelectric conversion layers 10 and 20 (each photoelectric conversion layer in three or more layers). Nitrogen atoms are added at an atomic concentration. Thereby, the open circuit voltage of the super straight type | mold laminated photoelectric conversion apparatus 200 increases by the effect similar to the effect obtained with the above-mentioned super straight type photoelectric conversion apparatus 100. FIG. Furthermore, when the nitrogen concentration is 0.01 to 10 atomic%, in addition to improving the open circuit voltage, the light transmittance of the n-type semiconductor layer is improved, so that the short-circuit current density is increased and the photoelectric conversion efficiency is further improved.

  In addition, when the n-type semiconductor layer is a microcrystalline silicon layer containing a nitrogen atom, it is preferable because the conductivity is high, the series resistance of the photoelectric conversion layer is reduced, and the shape factor is improved. Further, when the n-type semiconductor layer includes a second n-type semiconductor layer and a first n-type semiconductor layer between the second n-type semiconductor layer and the i-type semiconductor layer, the first n-type semiconductor layer Nitrogen atoms are not actively added to the layer, the nitrogen concentration of the second n-type semiconductor layer can be 4 to 10 atomic%, the open circuit voltage, the short circuit current density, and the form factor increase, This is preferable because the conversion efficiency is further improved.

  More preferably, if the i layer adjacent to the first n-type semiconductor layer is a microcrystalline silicon layer, not only does the i layer not deteriorate, but also the i / n of the first n-type semiconductor layer has. Since the layer interface recombination reduction effect is further enhanced and the form factor is increased, higher photoelectric conversion efficiency can be obtained. Similarly to Embodiment 1, it is preferable that the p-type semiconductor layer of the first and second photoelectric conversion layers is a layer containing at least one of carbon atoms and nitrogen atoms as impurities from the viewpoint of improving photoelectric conversion efficiency. .

  When the second embodiment is applied to a substrate type structure, the electrode 16 is on the light incident side unlike the super straight type stacked photoelectric conversion device 200, and therefore the first photoelectric conversion in the above description. The point where the positions of the layer 10 and the second photoelectric conversion layer 20 interchange with each other, the point where each photoelectric conversion layer 10, 20 is in the joining order of the pins from the electrode 16 side (light incident side), and the surface as the electrode 16 is uniform. It is necessary to pay attention to the grid shape that is not covered with, but all the obtained effects are the same as those of the super straight type structure.

As described above, according to the present invention, in the photoelectric conversion device and the stacked photoelectric conversion device, the open-circuit voltage, the short-circuit current density, and the form factor are increased without using a material that increases the carbon dioxide emission during production. The photoelectric conversion efficiency can be improved.
Examples of the present invention and comparative examples will be described below.

(Examples 1-8)
In the present Examples 1-8, the super straight type photoelectric conversion apparatus 100 shown in FIG. 1 was produced as follows.
As the substrate 11, a white plate glass (Asahi Glass Co., Ltd., trade name: Asahi-U) having a length of 127 mm × width 127 mm × thickness 1.8 mm in which a transparent conductive film 11 b is formed on the surface of a light-transmitting substrate 11 a was used. . A zinc oxide layer having a thickness of 50 nm is formed on the substrate 11 by a magnetron sputtering method, and then the photoelectric conversion layer 10 is formed by a plasma CVD method under the conditions described later, the p-type semiconductor layer 12, the i-type semiconductor layer 13, and the n-type semiconductor. Layer 14 was deposited in that order. The plasma CVD apparatus used for film formation of the photoelectric conversion layer 10 is an ultra-high vacuum apparatus, and a high-quality photoelectric conversion layer with little mixing of impurity elements can be manufactured. Subsequently, a 50 nm-thickness zinc oxide layer as the transparent conductive layer 15 and a 500 nm-thickness silver layer as the electrode 16 are sequentially deposited on the photoelectric conversion layer 10 by the magnetron sputtering method. 100 was obtained.

Each layer of the photoelectric conversion layer 10 was formed under the following conditions.
The p-type semiconductor layer 12 uses SiH ₄ , H ₂ , and B ₂ H ₆ as source gases. The H ₂ / SiH ₄ gas flow rate ratio was 150 times, and the B ₂ H ₆ / SiH ₄ gas flow rate ratio was 0.003. The p-type semiconductor layer 12 is desirably thin as long as it does not impair the function as the p-type layer in order to increase the amount of light incident on the i-type semiconductor layer, which is a photoactive layer. In this embodiment, the p-type semiconductor layer 12 has a thickness of 20 nm. did.
The i-type semiconductor layer 13 uses SiH ₄ and H ₂ as source gases. The H ₂ / SiH ₄ gas flow rate ratio was 80 times, and the film was formed to a film thickness of 2500 nm.
The n-type semiconductor layer 14 uses SiH ₄ , H ₂ , PH ₃ and N ₂ as source gases. The H ₂ / SiH ₄ gas flow rate ratio was 100 times, and the PH ₃ / SiH ₄ gas flow rate ratio was changed as shown in Table 1. N ₂ / SiH ₄ also gas flow rate was varied as described in Table 1 were also shown the membrane in a nitrogen concentration at the time shown in Table 1. The nitrogen concentration in the film is a value (atomic%) obtained as a result of performing highly sensitive secondary ion mass spectrometry for the n-type semiconductor layer 14. Further, in the Raman scattering spectrum of the single layer of the n-type semiconductor layer 14 of this example, a peak of crystalline silicon near 520 cm ⁻¹ attributed to the silicon-silicon bond was observed, and thus the n-type semiconductor of this example It was confirmed that the layer had a crystalline silicon phase. Further, the ratio Ic / Ia of the peak height Ic of the crystalline silicon with respect to the peak height Ia of amorphous silicon near 480 cm ⁻¹ was 3 or more. The n-type semiconductor layer 14 is desirably thin so as not to impair the function as the n-type layer in order to increase the amount of reflected light that reenters the i-type semiconductor layer 13 that is the photoactive layer from the back electrode 16. Thickness.
In addition, when forming each semiconductor layer 12, 13, and 14 by plasma CVD, the substrate temperature at the time of film-forming was 170 degreeC, 180 degreeC, and 160 degreeC, respectively.

The photoelectric conversion devices of Examples 1 to 8 thus obtained were measured for current-voltage characteristics with a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions. The results are summarized in Table 1. In particular, FIG. 3 shows the nitrogen concentration dependency of the open circuit voltage, FIG. 4 shows the nitrogen concentration dependency of the short circuit current density, and FIG. 5 shows the nitrogen concentration dependency of the photoelectric conversion efficiency. It was.

(Example (reference example) 9-11)
In Examples 9-11, except for the n-type semiconductor layer 14, the super straight type photoelectric conversion device 100 was manufactured as follows under the same conditions as in Examples 6-8.
The n-type semiconductor layer 14 was formed by forming a first n-type semiconductor layer to which nitrogen was not added and depositing a second n-type semiconductor layer having the same nitrogen concentration as in Examples 6 to 8 thereon. The first n-type semiconductor layer used SiH ₄ , H ₂ and PH ₃ as source gases. The H ₂ / SiH ₄ gas flow rate ratio was 70 times, and the PH ₃ / SiH ₄ gas flow rate ratio was 0.001. In the Raman scattering spectrum of the first n-type semiconductor layer single layer, the peak of crystalline silicon near 520 cm ⁻¹ was observed. Therefore, the first n-type semiconductor layers of Examples 9 to 11 have crystalline silicon phases. It was confirmed that it had. As shown in Table 1, the second n-type semiconductor layer was formed under the same conditions as in Examples 6-8. The film thicknesses of the first and second n-type semiconductor layers were 10 nm and 15 nm, respectively.

The photoelectric conversion devices of Examples 9 to 11 thus obtained were measured for current-voltage characteristics with a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions. The results are shown in Table 1 and FIGS. 3 to 5 in the same manner as in Examples 1-8.

(Example 12)
In Example 12, except that the H ₂ / SiH ₄ flow rate ratio at the time of forming the n-type semiconductor layer 14 was increased by 20 times, the super straight type photoelectric conversion device 100 was prepared as follows under the same conditions as in Example 6. Produced. That is, as shown in Table 1, the nitrogen concentration of the n-type semiconductor layer of Example 12 is 2 atomic%. In the Raman scattering spectrum of the single n-type semiconductor layer of this example, no crystalline silicon peak near 520 cm ⁻¹ was observed, confirming that the n-type semiconductor layer 14 of this example was made of amorphous silicon. It was.

The photoelectric conversion device of Example 12 obtained in this manner was measured for current-voltage characteristics with a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions. The results are shown in Table 1 and FIGS. 3 to 5 in the same manner as in Examples 1-8.

(Comparative Example 1)
In this comparative example 1, except for the n-type semiconductor layer 14, the super straight type photoelectric conversion device 100 was manufactured as follows under the same conditions as in Examples 1 to 8.
The n-type semiconductor layer 14 uses SiH ₄ , H ₂ , and PH ₃ as source gases, the H ₂ / SiH ₄ gas flow rate ratio is 20 times, and the PH ₃ / SiH ₄ gas flow rate ratio is such that the phosphorus concentration in the film is 0. All were prepared under the same conditions as in Examples 1 to 8, except that the concentration was adjusted to 0.01 atomic%. Since the peak of crystalline silicon near 520 cm ⁻¹ was not observed in the Raman scattering spectrum of the single n-type semiconductor layer of Comparative Example 1, the n-type semiconductor layer 14 of Comparative Example 1 may be made of amorphous silicon. confirmed.

The photoelectric conversion device of Comparative Example 1 thus obtained was measured for current-voltage characteristics with a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions. The results are shown in Table 1 and FIGS. 3 to 5 in the same manner as in Examples 1-8.

(Comparative Example 2)
In Comparative Example 2, a super straight photoelectric conversion device 100 was manufactured as follows under the same conditions as in Examples 1 to 8 except for the n-type semiconductor layer 14.
The n-type semiconductor layer 14 was produced under the same conditions as in Examples 1 to 8 except that the PH ₃ / SiH ₄ gas flow rate ratio and the N ₂ / SiH ₄ gas flow rate ratio were as shown in Table 1.

The photoelectric conversion device of Comparative Example 2 thus obtained was measured for current-voltage characteristics with a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions. The results are shown in Table 1. However, since the open circuit voltage, the short circuit current density, and the photoelectric conversion efficiency of Comparative Example 2 were all extremely low, they are shown in Table 1 but not shown in FIGS.

(Consideration about Examples 1 to 11 and Comparative Examples 1 and 2)
Hereinafter, the comparison results of Examples 1 to 11 and Comparative Examples 1 and 2 will be considered based on Table 1 and FIG.
Since the n-type semiconductor layer of Comparative Example 1 that did not use N ₂ gas at the time of forming the n-type semiconductor layer contains 0.0002 atomic% of nitrogen, the plasma CVD apparatus used in Examples 1 to 8 It is shown that nitrogen impurities present as degassed or residual gas in the vacuum chamber are very slightly mixed into the n-type semiconductor layer during film formation. However, since the plasma CVD apparatus is an ultra-high vacuum apparatus, the comparative example 1 is compared with other examples or comparative examples on the assumption that the amount of impurity nitrogen in the n-type semiconductor layer is the smallest.

  Since Example 1 in which the nitrogen concentration is lower than 0.001 atomic% is a nitrogen concentration at which neither the increase of the band gap due to the addition of nitrogen nor the passivation effect of the crystal grain boundary or the i / n layer interface can be obtained so much. It is considered that the open circuit voltage did not change much from 1. In Comparative Example 1, the open-circuit voltage is 0.500 V, whereas in Examples 2 to 8 in which the n-type semiconductor layer is formed so that the nitrogen concentration is 0.001 atomic% or more, this value is all A higher open circuit voltage was obtained. In particular, in Example 6, the effect of improving the open circuit voltage was maximized, and an open circuit voltage of 0.543 V was obtained. That is, in order to greatly improve the open circuit voltage, the nitrogen concentration in the n-type semiconductor layer is preferably 0.001 atomic% or more.

  In Comparative Example 2 where the nitrogen concentration is 13 atomic%, the open circuit voltage is 0.464 V, which is much lower than the open circuit voltage of Comparative Example 1. In addition, the short circuit current density and the shape factor are also greatly reduced and the photoelectric conversion efficiency is reduced to near zero. Therefore, by adding excessive nitrogen to the n-type semiconductor layer, the silicon nitride phase that is an insulator is added. It is considered that the electrical conductivity is decreased due to the increase in the ratio of the photogenerated carriers, and the collection efficiency of the photogenerated carriers is extremely decreased.

In Examples 1 to 8 and Comparative Example 1, the PH ₃ / SiH ₄ gas flow ratio was controlled so that the conductivity of the n-type semiconductor layer was 1 to 2 × 10 ⁻³ [S / cm]. The n-type semiconductor layer of Comparative Example 2 had a conductivity of 1 × 10 ⁻⁶ [S / cm], and the conductivity was lower than the others. Further, in Examples 4 to 8, since the PH ₃ / SiH ₄ gas flow rate ratio necessary for maintaining the same conductivity is increased, the activation efficiency of phosphorus as a dopant decreases with an increase in nitrogen concentration. In particular, it was found that in the comparative example 2 in a region higher than 10 atomic%, it was extremely lowered. For comparison, an n-type semiconductor layer single film was formed under a high concentration condition of 20 atomic% where the nitrogen concentration was higher than that of Comparative Example 2, and the PH ₃ / SiH ₄ gas flow ratio at that time was 10 times that of Comparative Example 2. However, the electrical conductivity was 1 × 10 ⁻⁷ [S / cm] or less, which was almost an insulator. From the above, in the region where the nitrogen concentration in the n-type semiconductor layer is higher than 10 atomic%, activation of phosphorus as a dopant is considered to be extremely difficult due to the increase in the silicon nitride phase as described above. It was found that the photoelectric conversion efficiency is greatly reduced when the necessary electrical conductivity is not obtained. That is, in order for the n-type semiconductor layer to have an appropriate conductivity and obtain an effect of improving the open-circuit voltage by adding nitrogen, it is preferable that the nitrogen concentration in the n-type semiconductor layer be 10 atomic% or less.
According to the above considerations, the present invention has a wide band gap, a crystal grain boundary and an i / n layer in the n-type semiconductor layer, particularly in the nitrogen concentration range of 0.001 to 10 atomic% in the n-type semiconductor layer. It is considered that a photoelectric conversion device with high open-circuit voltage and high photoelectric conversion efficiency can be obtained due to the passivation effect of the interface.

In addition, in Examples 7 and 8, the reason why the open-circuit voltage and the form factor are sequentially decreased as the nitrogen concentration is increased as compared with Example 6 in which the open-circuit voltage is maximized will be discussed below. As the nitrogen concentration in the n-type semiconductor layer approaches the high concentration region of 10 atomic% from the low concentration side, the band gap of the n-type semiconductor layer increases, and the valence band caused by the difference in the band gap at the interface of the i / n layer. It is thought that the discontinuity of becomes remarkable. Here, if recombination through i / n layer interface defects is negligibly small, if there is a barrier that blocks the discontinuity of the valence band, that is, diffusion of holes from the i layer to the n layer, Since the probability of hole existence near the interface of the i / n layer is reduced, a recombination reduction effect can be obtained accordingly. However, as is generally known, in actual microcrystalline solar cells or amorphous solar cells, defects exist at the interface of the p / i layer or i / n layer. It is believed that the recombination through i / n interface defects increases with increasing valence band discontinuity, which reduces the open circuit voltage and form factor. Therefore, in order to reduce recombination through interface defects, it is considered that the presence of an internal electric field is important in order to efficiently collect photocarriers in the vicinity of the interface so that they are not easily trapped by defects. As a means for realizing this, by inserting a layer having a band gap that relaxes the discontinuity of the valence band from the i layer to the n layer at the i / n layer interface, an internal electric field is applied to the entire inserted interface layer. Since it is applied, it is considered that the collection of photocarriers can be improved. 3 and 4, the open-circuit voltage and the short-circuit current density of Examples 9 to 11 in which the first n-type semiconductor layer to which nitrogen is not added is provided at the i / n layer interface correspond to the corresponding nitrogen concentrations. This is also supported by the fact that it is higher than Examples 6-8. That is, in the region where the nitrogen concentration in the second n-type semiconductor layer is 4 atomic% or more, the first n-type semiconductor layer made of microcrystalline silicon is inserted into the i / n layer interface, whereby the i / n layer Since the discontinuity of the valence band generated at the interface is relaxed, it is considered that the interface recombination is reduced and the open-circuit voltage, the short-circuit current density, and the form factor are increased to improve the photoelectric conversion efficiency. Further, when a second n-type semiconductor layer containing 13 atom% nitrogen corresponding to Comparative Example 2 was formed on the first n-type semiconductor layer to which nitrogen was not added, a photoelectric conversion device was manufactured. Comparative Example 2, the electrical conductivity of the second n-type semiconductor layer was extremely small, so that the open-circuit voltage, the short-circuit current density, and the form factor were greatly reduced, and the photoelectric conversion efficiency was reduced to nearly zero. From this, in the range of nitrogen concentration of 10 atomic% or less where the electric conductivity of the second n-type semiconductor layer is appropriate, by providing the first n-type semiconductor layer, the open circuit voltage, the short-circuit current density, and It became clear that the form factor increased.
According to the above consideration, when the nitrogen concentration in the second n-type semiconductor layer is in the range of 4 to 10 atomic%, the i / n layer interface is formed by forming the first n-type semiconductor layer to which nitrogen is not added. It is considered that the recombination is reduced and the shape factor is improved, and the open-circuit voltage and the short-circuit current density are increased to further improve the photoelectric conversion efficiency.

Next, the short-circuit current densities of Examples 1 to 8 and Comparative Examples 1 and 2 will be considered based on FIG. According to FIG. 4, it can be seen that there is almost no difference in short-circuit current density in Comparative Example 1, Example 1, and Example 2. In Comparative Example 1, the short-circuit current density is 21.80 mA / cm ² , whereas in Examples 3 to 8 in which the n-type semiconductor layer is formed so that the nitrogen concentration is 0.01 atomic% or more, all are A short-circuit current density exceeding this value was obtained, and the short-circuit current density continued to increase with increasing nitrogen concentration up to a nitrogen concentration of 10 atomic%. Therefore, by increasing the nitrogen concentration in the n-type semiconductor layer, the light transmittance of the n-type semiconductor layer is improved in the region where the nitrogen concentration is 0.01 atomic% or more, and the electrode 16 provided on the back surface is improved. Since the number of photogenerated carriers increases because the amount of light that is reflected and re-enters the i-type semiconductor layer 13 increases, it is considered that the short-circuit current density increases. Further, when the light transmittances of the n-type semiconductor layer single films of Examples 1 to 8 and Comparative Examples 1 and 2 were measured and compared, the light transmittance at wavelengths of 600 nm to 1150 nm was improved as the nitrogen concentration increased. This is considered to be because the ratio of the silicon nitride phase having a high light transmittance increases as the nitrogen concentration in the n-type semiconductor layer increases. In Comparative Example 2, the short-circuit current density decreases due to the decrease in electrical conductivity that occurs accompanying the increase in the silicon nitride phase having a high light transmittance in the n-type semiconductor layer, but as in Examples 3-8. It was revealed that a high short-circuit current density can be obtained in a region where the nitrogen concentration is 10 atomic% or less.
According to the above consideration, in the range where the nitrogen concentration in the n-type semiconductor layer is 0.01 to 10 atomic%, in addition to the improvement of the open-circuit voltage described above, the short-circuit current density is improved by the improvement of the light transmittance of the n-type semiconductor layer. Since it increases, it is thought that a photoelectric conversion apparatus with higher photoelectric conversion efficiency can be obtained.

(Comparison with Example 6 and Example 12)
Next, the comparison results of Examples 6 and 12 will be considered. Example 12 is an amorphous silicon n-type semiconductor layer doped with nitrogen because the amount of hydrogen dilution during the deposition of the n-type semiconductor layer is small, whereas Example 6 has a large amount of hydrogen dilution and nitrogen. The difference is that it is an added microcrystalline silicon n-type semiconductor layer. This indicates that when the Raman scattering spectra of the n-type semiconductor layers of Examples 6 and 12 were measured, a peak near 520 cm ⁻¹ indicating the presence of a crystalline silicon phase was found in the n-type semiconductor layer of Example 6. Although observed, it was confirmed that the peak was not observed in the n-type semiconductor layer of Example 12.
As shown in Table 1, the shape factor of Example 12 is 0.681, whereas the shape factor of Example 6 is 0.720, and the shape factor is greatly improved. Therefore, by making the n-type semiconductor layer a layer containing crystalline silicon, the electrical conductivity is improved, and the series resistance loss of the photoelectric conversion device is reduced, so that the open-circuit voltage, the short-circuit current density, and the form factor increase. It is thought that high photoelectric conversion efficiency could be obtained.

(Examples 13 to 15)
In Examples 13 to 15, a super straight type photoelectric conversion device 100 was manufactured as follows under the same conditions as Example 6 except for the p-type semiconductor layer 12.
The p-type semiconductor layer 12 uses SiH ₄ , H ₂ , B ₂ H ₆ , N _2, and CH ₄ as source gases, the H ₂ / SiH ₄ gas flow rate ratio is 150 times, and B ₂ H ₆ / SiH ₄ The gas flow rate ratio, CH ₄ / SiH ₄ gas flow rate ratio, and N ₂ / SiH ₄ flow rate ratio are as shown in Table 2. All other conditions were the same as in Example 6. Therefore, the nitrogen concentration of the n-type semiconductor layer 14 of Examples 13 to 15 is 2 atomic%. The carbon concentration and nitrogen concentration in the film of the p-type semiconductor layer 12 at this time are shown in Table 2.

For the photoelectric conversion device of Example 13 to 15 obtained in this manner, AM1.5 (100mW / cm ²⁾ cell area 1 cm ² of current under the irradiation condition - voltage characteristics were measured. The results are summarized in Table 2.

(Consideration about Example 6 and Examples 13-15)
Consider the comparison results of Example 6 and Examples 13-15. In Examples 13 to 15, higher open-circuit voltage and short-circuit current density were obtained than in Example 6, and thus higher photoelectric conversion efficiency was obtained. As in Examples 13 and 14, the reason why the short-circuit current increases when the p-type semiconductor layer 12 contains carbon atoms or nitrogen atoms is that the p-type semiconductor layer 12 contains the impurity atoms, so that the band gap is This is thought to be due to an increase in light transmittance.
From the above, it is preferable to use a carbon-containing p-type semiconductor layer or a nitrogen-containing p-type semiconductor layer for the p-type semiconductor layer 12 because the photoelectric conversion efficiency of the photoelectric conversion device 100 is further improved.
Further, as in Example 15, when both the carbon atom and the nitrogen atom are contained as impurities in the p-type semiconductor layer 12, the open-circuit voltage is further increased as compared with the case where only one of the carbon atom or the nitrogen atom is contained. The photoelectric conversion efficiency was improved by improving the short-circuit current density.

(Example 16)
In Example 16, the super straight stacked photoelectric conversion device shown in FIG. 2 was produced as follows.
As the substrate 11, the same white glass having a transparent conductive film formed on the surface thereof as used in the above Examples 1 to 15 was used. A 50 nm zinc oxide layer is formed on the substrate 11 by a magnetron sputtering method, and then the first photoelectric conversion layer 10 is formed by a plasma CVD method under the conditions described later, the p-type semiconductor layer 12, the i-type semiconductor layer 13, and the n-type semiconductor layer. The semiconductor layers 14 were deposited in this order. A second photoelectric conversion layer 20 is further deposited on the p-type semiconductor layer 22, the i-type semiconductor layer 23, and the n-type semiconductor layer 24 in this order under the conditions described later, and then the film is formed as the transparent conductive layer 15 by magnetron sputtering. A 50 nm thick zinc oxide layer was deposited as an electrode 16 and a 500 nm thick silver layer was deposited to obtain a super straight stacked photoelectric conversion device 200.

The first photoelectric conversion layer 10 did not use N ₂ gas when the n-type semiconductor layer 14 was formed, and the second photoelectric conversion layer 20 used N ₂ gas when the n-type semiconductor layer 24 was formed. The p-type semiconductor layer 12 uses SiH ₄ , H ₂ , and B ₂ H ₆ as source gases, the H ₂ / SiH ₄ gas flow ratio is 5 times, and the B ₂ H ₆ / SiH ₄ gas flow ratio is a film. The medium boron concentration was adjusted to 0.1 atomic%. The film thickness of the p-type semiconductor layer 12 was 15 nm.
The i-type semiconductor layer 13 uses SiH ₄ and H ₂ as source gases. The H ₂ / SiH ₄ gas flow rate ratio was 20 times and the film thickness was 300 nm.
The n-type semiconductor layer 14 used SiH ₄ , H ₂ , and PH ₃ as source gases. The H ₂ / SiH ₄ gas flow rate ratio was 5 times, and the PH ₃ / SiH ₄ gas flow rate ratio was adjusted so that the phosphorus concentration in the film was 0.01 atomic%. The film thickness of the n-type semiconductor layer 14 was 20 nm.
In addition, when forming each semiconductor layer 12, 13, and 14 by plasma CVD, all the substrate temperatures at the time of film-forming were 200 degreeC.
The film forming conditions and film thicknesses of the p-type semiconductor layer 22, the i-type semiconductor layer 23, and the n-type semiconductor layer 24 of the second photoelectric conversion layer 20 are respectively the p-type semiconductor layer 12 and the i-type semiconductor layer 13 of Example 6. And the same as the n-type semiconductor layer 14. Therefore, the nitrogen concentration in the n-type semiconductor layer 24 is 2 atomic%.
For the photoelectric conversion device of Example 16 obtained in this manner, the current-voltage characteristics of a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions were measured in the same manner as in the above example. Are shown in Table 3.

(Example 17)
A super straight stacked photoelectric conversion device 200 was manufactured under the same conditions as in Example 16 except for the n-type semiconductor layer 14. In this example, N ₂ gas was used when the n-type semiconductor layers 14 and 24 of the first and second photoelectric conversion layers 10 and 20 were formed. The H ₂ / SiH ₄ gas flow rate ratio at the time of forming the n-type semiconductor layer 14 is adjusted to 5 times, and the PH ₃ / SiH ₄ gas flow rate ratio is adjusted so that the phosphorus concentration in the film is 0.01 atomic%, and N ₂ / The SiH ₄ gas flow rate ratio was adjusted so that the nitrogen concentration in the film was 2 atomic%.
For the photoelectric conversion device of Example 17 obtained in this way, the current-voltage characteristics of a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions were measured in the same manner as in the above example. Are shown in Table 3.

(Comparative Example 3)
A super straight stacked photoelectric conversion device 200 was manufactured under the same conditions as in Example 16 except for the n-type semiconductor layer 24. In Comparative Example 3, N ₂ gas was not used when the n-type semiconductor layers 14 and 24 of the first and second photoelectric conversion layers 10 and 22 were formed. The H ₂ / SiH ₄ gas flow rate ratio during the formation of the n-type semiconductor layer 24 was adjusted to 20 times, and the PH ₃ / SiH ₄ gas flow rate ratio was adjusted so that the phosphorus concentration in the film was 0.01 atomic%.
Similarly to the above example, the current-voltage characteristics of a cell area of 1 cm ² under AM1.5 (100 mW / cm ² ) irradiation conditions were measured, and the results are shown in Table 3.

(Consideration on Examples 16 and 17 and Comparative Example 3)
Hereinafter, the comparison results of Examples 16 and 17 and Comparative Example 3 will be considered based on Table 3.
Compared with Comparative Example 3 in which the n-type semiconductor layers of the first and second photoelectric conversion layers hardly contain nitrogen atoms, the n-type semiconductor layer of the second photoelectric conversion layer contains 2 atom% of nitrogen atoms. In Example 16, the open circuit voltage and the short circuit current density were large, and high conversion efficiency was obtained. This is considered to be because in the second photoelectric conversion layer 20, the same open-circuit voltage improvement effect as in Examples 2 to 8 and the same short-circuit current density improvement effect as in Examples 3 to 8 were obtained.
Furthermore, in Example 17 in which the n-type semiconductor layers of the first and second photoelectric conversion layers both contain 2 atomic% of nitrogen atoms, the first photoelectric conversion layer is also open-circuited in addition to the second photoelectric conversion layer. Since the effect of improving the short circuit current density was obtained, a higher conversion efficiency than that of Example 16 was obtained.
According to the above consideration, if the present invention is applied to at least one n-type semiconductor layer in a stacked photoelectric conversion device, the photoelectric conversion efficiency is increased by increasing the open-circuit voltage and the short-circuit current density as in the single-layer photoelectric conversion device. Can be improved.

In addition, this invention is not limited to the said Example, Various parameters in a photoelectric conversion apparatus, for example, a p-type semiconductor layer, an i-type semiconductor layer, an n-type semiconductor layer (or 1st, 2nd photoelectric conversion layer) ), The film thickness of the transparent conductive layer and the electrode, the nitrogen concentration and / or the impurity concentration in the p-type semiconductor layer and the n-type semiconductor layer (or the first and second photoelectric conversion layers) can be appropriately changed, and Various parameters at the time of manufacturing the photoelectric conversion device, for example, N ₂ / SiH ₄ flow rate ratio, B ₂ H ₆ / SiH ₄ flow rate ratio, CH ₄ / SiH ₄ flow rate ratio, PH ₃ / SiH ₄ flow rate ratio, H ₂ / The SiH ₄ flow rate ratio, the film formation method of each layer, the film formation temperature, and the like can be changed as appropriate.

  The photoelectric conversion device of the present invention is suitable as a super straight type or substrate type thin film solar cell.

It is a schematic sectional drawing of the super straight type photoelectric conversion apparatus of Embodiment 1 of this invention. It is a schematic sectional drawing of the super straight type | mold laminated photoelectric conversion apparatus of Embodiment 2 of this invention. It is a graph which shows the nitrogen concentration dependence in the n-type semiconductor layer film of the open circuit voltage in Examples 1-12 and Comparative Example 1. It is a graph which shows the nitrogen concentration dependence in the n-type semiconductor layer film of the short circuit current density in Examples 1-12 and Comparative Example 1. It is a graph which shows the nitrogen concentration dependence in the n-type semiconductor layer film of the photoelectric conversion efficiency in Examples 1-12 and Comparative Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 20 Photoelectric conversion layer 11 Substrate 11a Translucent substrate 11b Transparent conductive layer 12, 22 p-type semiconductor layer 13, 23 i-type semiconductor layer 14, 24 n-type semiconductor layer 15 Transparent conductive layer 16 Electrode 100 Super straight type photoelectric conversion Device 200 Super straight type stacked photoelectric conversion device

Claims (11)

a p-type semiconductor layer; an i-type semiconductor layer; and an n-type semiconductor layer containing at least silicon atoms, the at least one pin-type photoelectric conversion layer, and the one or more pin-type photoelectric layers At least one of the n-type semiconductor layers in the conversion layer contains nitrogen atoms ;
The n-type semiconductor layer containing a nitrogen atom has a concentration of nitrogen atoms contained in the n-type semiconductor layer of 0.001 to 10 atom% and has a crystalline silicon phase . 2. The photoelectric conversion device according to claim 1 , wherein the n-type semiconductor layer containing nitrogen atoms has a concentration of nitrogen atoms contained in the n-type semiconductor layer of 0.01 to 10 atomic%. The photoelectric conversion device according to claim 1 or 2 , wherein the n-type semiconductor layer containing a nitrogen atom has a crystallization ratio of 3 or more. i-type semiconductor layer, the photoelectric conversion device according to any one of claims 1 to 3 containing silicon atoms as the crystalline silicon phase. p-type semiconductor layer, the photoelectric conversion device according to any one of claims 1-4 containing carbon atoms and / or nitrogen atoms. The photoelectric conversion device according to any one of claims 1 to 5 , wherein two or more pin-type photoelectric conversion layers are provided. The photoelectric conversion apparatus of Claim 6 which has a translucent electrically conductive film between two or more pin type photoelectric conversion layers. Forming one or more photoelectric conversion layers including a p-type semiconductor layer, an i-type semiconductor layer, and an n-type semiconductor layer via a conductive film on a substrate;
In the step of forming the n-type semiconductor layer of the photoelectric conversion layer, a nitrogen atom concentration with respect to the silicon atom concentration is 0.001 to 10 atomic% using a source gas containing silicon atoms, an n-type conductive element, and nitrogen atoms. A method for manufacturing a photoelectric conversion device , comprising forming a nitrogen atom so that an n-type semiconductor layer containing a nitrogen atom has a crystalline silicon phase . The source gas for forming the n-type semiconductor layer containing nitrogen atoms is N ₂ The manufacturing method of the photoelectric conversion apparatus of Claim 8 containing this. Raw material gas for forming the n-type semiconductor layer containing nitrogen atoms comprises N ₂ and SiH _4, N ₂ / claim 8 or 9, the gas flow ratio of SiH ₄ is controlled to a range of 0.0002 to 2 The manufacturing method of the photoelectric conversion apparatus of description. Raw material gas for forming the n-type semiconductor layer containing nitrogen atoms further comprises a PH _3, claim 10 for controlling the gas flow rate ratio of PH ₃ / SiH ₄ in the range of 0.0125 to 0.025 Method for manufacturing a photoelectric conversion device.

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