JP2010267860A - Method of manufacturing stacked photoelectric conversion device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a high performance stacked photoelectric conversion device capable of increasing the production efficiency while increasing flexibility in its manufacturing step. <P>SOLUTION: The problem is solved by the method of manufacturing the stacked photoelectric conversion device which includes a plurality of photoelectric conversion units and in which a reverse-conductivity type layer 33 in a forward photoelectric conversion unit 3 which is relatively positioned on the light incident side at least partially includes a silicon composite layer. The method includes: the plasma CVD (Chemical Vapor Deposition) step; the step of forming the silicon composite layer; the step of temporarily taking out the silicon composite layer to the atmosphere and exposing its outermost surface to the atmosphere as the step which comes directly after the above step; and the step of forming a one conductivity type crystalline substance film of a backward photoelectric conversion unit 4 as the step which comes directly after the above step, wherein the power density/film-formation pressure of the step of forming the one conductivity type crystalline substance film of the backward photoelectric conversion unit is at least 0.01 times and less than 0.8 times that of the step of forming the silicon composite layer. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a stacked photoelectric conversion device, and not only to provide a high-performance photoelectric conversion device, but also to a manufacturing method that can increase the flexibility of the manufacturing process and improve the production efficiency.

In recent years, in order to achieve both cost reduction and high efficiency of a photoelectric conversion device, a thin film photoelectric conversion device that has almost no problem in terms of resources has attracted attention and has been vigorously developed. Thin film photoelectric conversion devices are expected to be applied to various applications such as solar cells, optical sensors, and displays.
An amorphous silicon photoelectric conversion device, which is one of thin film photoelectric conversion devices, can be formed on a large-area glass substrate or stainless steel substrate at a low temperature, so that cost reduction can be expected.

  A thin film photoelectric conversion device generally includes a first electrode, a surface of which is laminated in order on an insulating substrate, one or more semiconductor thin film photoelectric conversion units, and a second electrode. One thin film photoelectric conversion unit is composed of an i-type layer sandwiched between a p-type layer and an n-type layer. Here, the photoelectric conversion unit or the thin-film solar cell has an amorphous i-type photoelectric conversion layer that occupies the main part regardless of whether the p-type and n-type conductivity type layers included therein are amorphous or crystalline. Those having a high quality are referred to as amorphous photoelectric conversion units or amorphous thin film solar cells, and those having a crystalline i-type layer are referred to as crystalline photoelectric conversion units or crystalline thin film solar cells.

  As a method for improving the conversion efficiency of a photoelectric conversion device, a photoelectric conversion device employing a so-called tandem structure in which two or more photoelectric conversion units are stacked is known. In this method, a front photoelectric conversion unit including a photoelectric conversion layer having a large band gap is disposed on the light incident side of the photoelectric conversion device, and a rear photoelectric conversion unit including a photoelectric conversion layer having a small band gap is sequentially arranged behind the photoelectric conversion layer. By arranging, photoelectric conversion can be performed over a wide wavelength range of incident light, thereby improving the conversion efficiency of the entire apparatus. (In the present application, a photoelectric conversion unit disposed relatively on the light incident side is referred to as a front photoelectric conversion unit, and a photoelectric conversion unit disposed adjacent to a side farther from the light incident side than this is referred to as a rear photoelectric conversion unit. Called a conversion unit.)

  Furthermore, a stacked photoelectric conversion device having a structure in which both a light transmitting property and a light reflecting property are interposed between a plurality of stacked photoelectric conversion units and a conductive intermediate reflective layer is interposed has recently been proposed. . In this case, a part of the light reaching the intermediate reflection layer is reflected, and the amount of light absorption in the front photoelectric conversion unit located on the light incident side of the intermediate reflection layer is increased, and is generated in the front photoelectric conversion unit. The current value can be increased. For example, when an intermediate reflective layer is inserted into a hybrid photoelectric conversion device composed of an amorphous silicon photoelectric conversion unit and a crystalline silicon photoelectric conversion unit, the amorphous silicon photoelectric conversion is performed without increasing the film thickness of the amorphous silicon layer. The current generated by the unit can be increased. Alternatively, the amorphous silicon photoelectric conversion unit due to photodegradation that becomes conspicuous as the thickness of the amorphous silicon layer increases because the thickness of the amorphous silicon layer necessary to obtain the same current value can be reduced. It is possible to suppress the deterioration of characteristics.

  Patent Document 1 states that “as viewed from the light incident side, one conductive type layer, a substantially intrinsic semiconductor photoelectric conversion layer, and a reverse conductive type layer are arranged in this order and are formed by a plasma CVD method. A method of manufacturing a stacked photoelectric conversion device including a plurality of conversion units, wherein the reverse conductivity type layer in the front photoelectric conversion unit disposed on the light incident side and the rear side of the front photoelectric conversion unit are disposed adjacent to each other. Forming a conductive type layer having at least a part of a silicon composite layer in which a silicon crystal phase is mixed in an amorphous alloy of silicon and oxygen in one or both of one conductive type layer in the rear photoelectric conversion unit And after the part of the silicon composite layer is formed, the silicon composite layer is once taken out into the atmosphere, and the outermost surface of the silicon composite layer is exposed to the atmosphere, and then the remaining silicon composite layer of the same conductivity type is formed. Have steps The production method "invention is disclosed.

JP 2005-277303 A

  In the method of manufacturing a photoelectric conversion device in which a plurality of power generation units are stacked, in Patent Document 1, an air exposure outermost surface layer and a layer formed immediately above the air exposure interface have an air exposure interface, but are formed under the same conditions. In the comparative example 11, when a layer different from the air exposure outermost surface layer is formed on the air exposure outermost surface layer, that is, when the air exposure surface is the power generation unit interface, the photoelectric conversion efficiency is lowered. Then it is described.

  In the first example, in the actual manufacturing method, it is possible to expose the air between the power generation units, and each power generation unit can be formed using a separate plasma CVD apparatus. The layer should be the same as the outermost surface layer exposed to the atmosphere. That is, the CVD apparatus that forms the rear unit needs equipment for forming a silicon composite layer that is the rearmost layer of the front photoelectric conversion unit that is the air-exposed surface.

  The first aspect of the present invention includes a plurality of photoelectric conversion units in which one conductivity type layer, a substantially intrinsic semiconductor photoelectric conversion layer, and a reverse conductivity type layer are arranged in this order as viewed from the light incident side. The reverse conductivity type layer in the front photoelectric conversion unit disposed relatively on the light incident side is reversely conductive having at least a part of a silicon composite layer in which a silicon crystal phase is mixed in an amorphous alloy of silicon and oxygen. A method of manufacturing a stacked photoelectric conversion device that is a mold layer, comprising a step of forming a one-conductivity-type layer, a substantially intrinsic semiconductor photoelectric-conversion layer, and a reverse-conductivity-type layer by a plasma CVD method, respectively. A step of forming at least the silicon composite layer of the reverse conductivity type layer of the front photoelectric conversion unit, and a step immediately after the step of exposing the outermost surface of the silicon composite layer to the atmosphere by taking it out into the atmosphere. Immediately after As a process, it has the process of forming the crystalline one conductivity type layer of the rear photoelectric conversion unit, and the power density / film forming pressure of the process of forming the crystalline one conductivity type layer of the rear photoelectric conversion unit is A stacked photoelectric conversion device having a power density / film-forming pressure of 0.01 to less than 0.8 times of the step of forming the silicon composite layer of the reverse conductivity type layer of the front photoelectric conversion unit It is a manufacturing method.

  The "exposure to the atmosphere" refers to the process of reducing the degree of vacuum from the previous process to atmospheric pressure, adjusting the set temperature in the previous process to bring it closer to the ambient temperature, Increase the degree of vacuum to reach the degree of vacuum in the process of forming the crystalline one-conductivity type layer of the rear photoelectric conversion unit, or the crystalline one-conductivity type layer of the rear photoelectric conversion unit from the ambient temperature exposed to the atmosphere This is a broad concept process including a process of reaching the set temperature of the process to be formed.

A second aspect of the present invention is to hydrogen flow rate / SiH ₄ gas flow rate during the silicon composite layer formed of front photoelectric conversion unit opposite conductivity type, the hydrogen flow rate at the one conductivity type layer formed in the rear unit formed thereon / SiH ₄ process gas flow, which is formed in the opposite conductivity type layer is than in hydrogen flow rate / SiH ₄ gas flow rate during the silicon composite layer formed is in the range of 1.2 times or less than 0.1 times the front photoelectric conversion unit It is a manufacturing method of the laminated photoelectric conversion apparatus of Claim 1 which has these.

  The present invention has an effect that a process of forming a continuation of the silicon composite layer of the front photoelectric conversion unit is not required in the step of forming the rear photoelectric conversion unit after exposure to the atmosphere.

  For example, in the case of using a CVD apparatus that forms one conductivity type layer, a photoelectric conversion layer, and a reverse conductivity type layer in separate film forming chambers, a rear one conductivity type layer is formed. It is not necessary to bring the substrate into the reverse conductivity type layer forming chamber before, and the productivity is greatly improved.

  In addition, for example, in the case of using a CVD apparatus that forms one conductivity type layer of the rear photoelectric conversion unit, an intrinsic semiconductor photoelectric conversion layer, and a reverse conductivity type layer all in the same film forming chamber, the rear one conductivity type layer It is no longer necessary to form the reverse conductivity type layer of the front electric conversion unit before forming the "impurity used for imparting the reverse conductivity type in the silicon composite layer that is the reverse conductivity type layer. The conventional problem itself such as “one conductive type layer of the photoelectric conversion unit and the photoelectric conversion layer further behind may be mixed” is eliminated.

  Whichever method of CVD apparatus is used, equipment for forming a silicon composite layer is not required in the CVD apparatus for forming the rear photoelectric conversion unit, and manufacturing equipment can be simplified.

  According to the present invention, it is possible to facilitate air extraction between the reverse conductivity type layer of the front photoelectric conversion unit and the one conductivity type layer of the rear photoelectric conversion unit, which is the boundary between the front photoelectric conversion unit and the rear photoelectric conversion unit. it can.

  The present invention has been completed by selecting parameters in a direction opposite to the common sense of those skilled in the art.

  For those skilled in the art, it has been desired that the outermost surface layer exposed to the atmosphere and the layer formed immediately after the exposure to the atmosphere should be the same conductivity type layer formed under the same conditions.

  On the other hand, in the case of a crystalline photoelectric conversion unit, those skilled in the art believe that one conductivity type layer of the photoelectric conversion unit is crystalline, and “a high power density is required to ensure sufficient crystallinity as the film quality of the one conductivity type layer. "

  In addition, there is an existing concept that “a p-type crystalline layer is harder to crystallize than an n-type crystalline layer”, and the p-type crystalline layer forming condition is set to a lower power density than the n-type crystalline layer forming condition. Never tried the direction to do.

  Further, as another common sense, since a low power density leads to a slow film forming speed, the direction of “having the disadvantage of extending the time required for the forming process” has never been tried.

  This time, when a person skilled in the art did an experimental study in a direction never performed, surprisingly, a remarkable effect appeared.

  In the CVD process, there are independent or closely related parameters such as a film forming temperature, a film forming pressure, a distance between electrodes, a gas flow rate ratio, and a power density.

  While there are a plurality of parameters to be examined, in the present invention, the parameter of power density / film forming pressure was found to be a dominant parameter over other conditions, and the present invention was completed.

  In the plasma CVD method, generally, the direction in which the film forming pressure is reduced is consistent with the direction in which the power density is increased. Therefore, when looking back after the completion of the present invention, the parameter of power density / film forming pressure of the present invention can be said to be an index that more effectively represents the magnitude of the power density.

  Although it was difficult to distinguish from the prior art only by the power density, it was possible to distinguish from the prior art by selecting the parameter of power density / film forming pressure. Thus, the parameter of power density / film forming pressure can be distinguished from the prior art, and is a valid parameter.

1 is a structural cross-sectional view of a stacked photoelectric conversion device according to an embodiment of the present invention.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. In the drawings of the present application, dimensional relationships such as thickness and length are appropriately changed for clarity and simplification of the drawings and do not represent actual dimensional relationships. Moreover, in each figure, the same referential mark represents the same part or an equivalent part.

  FIG. 1 is a cross-sectional view of a stacked photoelectric conversion device according to an example of an embodiment of the present invention. On the transparent substrate 1, the transparent electrode layer 2, the front photoelectric conversion unit 3, the rear photoelectric conversion unit 4, and the back electrode layer 5 are arranged in this order.

A plate-like member or a sheet-like member made of glass, transparent resin, or the like is used for the transparent substrate 1 used in a photoelectric conversion device of a type in which light enters from the substrate side. The transparent electrode layer 2 is preferably made of a conductive metal oxide such as SnO ₂ or ZnO, and is preferably formed using a method such as CVD, sputtering, or vapor deposition. The transparent electrode layer 2 desirably has the effect of increasing the scattering of incident light by having fine irregularities on its surface.

As the back electrode layer 5, it is preferable to form at least one metal layer made of at least one material selected from Al, Ag, Au, Cu, Pt and Cr by sputtering or vapor deposition. Between the photoelectric conversion unit and the metal electrode, ITO, may be formed a layer made of SnO 2, conductive oxides such as _ZnO (not shown).

  A photoelectric conversion semiconductor layer composed of a plurality of photoelectric conversion units is disposed behind the transparent electrode 2. In the case of a structure in which two photoelectric conversion units are stacked as shown in FIG. 1, the front photoelectric conversion unit 3 disposed on the light incident side has a relatively wide bandgap material, for example, an amorphous silicon-based material. A conversion unit or the like is used. The rear photoelectric conversion unit 4 arranged on the rear side includes a material having a relatively narrow band gap, for example, a photoelectric conversion unit made of a silicon-based material containing crystalline material, an amorphous silicon germanium photoelectric conversion unit, or the like. Used.

  Each photoelectric conversion unit is preferably configured by a pin junction including a one-conductivity type layer, an i-type layer that is a substantially intrinsic photoelectric conversion layer, and a reverse conductivity type layer. Among these, those using amorphous silicon for the i-type layer are called amorphous silicon photoelectric conversion units, and those using crystalline silicon are called crystalline silicon photoelectric conversion units. Note that the amorphous or crystalline silicon-based material is not only a case where only silicon is used as a main element constituting a semiconductor, but also an alloy material including elements such as carbon, oxygen, nitrogen, and germanium. Good.

  In the structure of FIG. 1, the one conductivity type layers 31 and 41 on the light incident side of each of the front photoelectric conversion unit and the rear photoelectric conversion unit are p-type layers, and correspondingly the opposite conductivity type layers 33 and 43 are n-type. Is a layer. The main constituent material of the conductive layer is not necessarily the same as that of the i-type layer. For example, amorphous silicon carbide can be used for the p-type (or n-type) layer of the amorphous silicon photoelectric conversion unit. In addition, a silicon layer containing crystal in an n-type (or p-type) layer (also called microcrystalline silicon) or a silicon composite layer containing a silicon crystal phase in an amorphous alloy can be used.

The two types of conductive layers play a role of generating a diffusion potential in the photoelectric conversion unit, and the open end voltage (V _oc ), which is one of the characteristics of the thin film photoelectric conversion device, is influenced by the magnitude of the diffusion potential. . However, these conductive layers are inactive layers that do not contribute to photoelectric conversion, and light absorbed here hardly contributes to power generation. Therefore, it is preferable that the conductive layer be as thin or transparent as possible within a range that generates a sufficient diffusion potential.

  In the present invention, a silicon composite layer characterized by containing a silicon crystal phase in an amorphous alloy of silicon and oxygen is used as an intermediate reflective layer in a stacked photoelectric conversion device. In order to function as an intermediate reflection layer, it is necessary to arrange the photoelectric conversion layer 32 at any position between the photoelectric conversion layer 32 in the front photoelectric conversion unit 3 and the photoelectric conversion layer 42 in the rear photoelectric conversion unit 4.

  The silicon composite layer can also serve as part or all of the conductive layer in the photoelectric conversion unit. Therefore, at least one reverse conductivity type or one conductivity type silicon composite layer is disposed in the region from the reverse conductivity type layer 33 in the front photoelectric conversion unit 3 to the one conductivity type layer 41 in the rear photoelectric conversion unit 4. do it.

In addition, since the silicon composite layer can also serve as a conductive type layer, the simplest structure is to replace all of the conductive type layers 33 and 43 with a silicon composite layer. All may be a silicon composite layer.
Further, the present invention is not limited to this, and a multi-layer structure with a conductive material (for example, conductive microcrystalline silicon or high-refractive-index conductive silicon oxide) according to the prior art is used, and the reverse conductive layer 33 or the single conductive type is formed in the entire multilayer structure. Layer 41 can also be formed. Alternatively, a multilayer structure in which silicon composite layers having different physical properties such as a refractive index are stacked, or a silicon composite layer in which physical properties are continuously changed in the stacking direction may be used.

An example of the conditions for forming the silicon composite layer in the present invention is specifically described as follows. SiH ₄ , CO ₂ , H ₂ , PH ₃ (or B ₂ H ₆ ) is used as a reaction gas, so-called microcrystal production conditions with a large H ₂ / SiH ₄ ratio, and a CO ₂ / SiH ₄ ratio of 2 or more. It can be produced by the plasma CVD method using this range. The conditions for plasma CVD at this time are, for example, a capacitively coupled parallel plate electrode, a power frequency of 10 to 100 MHz, a power density of 50 to 500 mW / cm ² , a film forming pressure of 50 to 1500 Pa, and a substrate temperature of 150 to 250 ° C. is there. When the CO ₂ / SiH ₄ ratio is increased, the oxygen concentration in the film increases monotonously.

  The feature of the present invention is that after the formation of the silicon composite layer, the substrate is once taken out into the atmosphere, and thereafter, a step of forming one conductive type layer or more of the rear photoelectric conversion unit immediately above is formed. An example of a specific embodiment will be described below as a procedure for forming a photoelectric conversion unit in the two-layer stacked photoelectric conversion device shown in FIG.

  That is, in this photoelectric conversion device, a substrate in which a transparent electrode 2 made of a transparent conductive oxide film (TCO) is formed on a transparent insulating substrate 1 such as glass is first introduced into a first plasma CVD device. Here, after forming the one conductive type layer 31 included in the front photoelectric conversion unit 3 and the substantially intrinsic semiconductor photoelectric conversion layer 32 on the transparent electrode 2, the reverse conductive type layer 33 including the silicon composite layer is formed by the plasma CVD method. Are sequentially deposited.

  Thereafter, the substrate is taken out from the first plasma CVD apparatus to the atmosphere, whereby the surface of the reverse conductivity type silicon composite layer 33 is exposed to the atmosphere. The substrate need not be in a cooled state when exposed to the atmosphere, and may be exposed at a high temperature of, for example, a substrate temperature of 100 ° C. or higher as long as it is safe.

  The "exposure to the atmosphere" refers to the process of reducing the degree of vacuum from the previous process to atmospheric pressure, adjusting the set temperature in the previous process to bring it closer to the ambient temperature, Increase the degree of vacuum to reach the degree of vacuum in the process of forming the crystalline one-conductivity type layer of the rear photoelectric conversion unit, or the crystalline one-conductivity type layer of the rear photoelectric conversion unit from the ambient temperature exposed to the atmosphere This is a broad concept process including a process of reaching the set temperature of the process to be formed. As described above, in the case where the substrate is not cooled when exposed to the atmosphere, the step of exposing to the atmosphere does not include a step of bringing the temperature close to the ambient temperature.

  Further, the phrase “as the immediately following process” means immediately after the order of the processes, and does not particularly limit the time interval between the processes.

  The silicon composite layer 33 before being exposed to the air preferably has a refractive index of 2.5 or less, or an oxygen concentration in the film of 25 atomic% or more with respect to light having a wavelength of 600 nm. The relationship between the refractive index and the oxygen concentration in the film has a relatively high correlation. It goes without saying that the lower the refractive index, the higher the function and effect of the intermediate reflection layer described above. The reason why the value of light having a wavelength of 600 nm is used as an index as the refractive index of the silicon composite layer is as follows. Spectral sensitivity of the amorphous silicon photoelectric conversion unit is one of the stacked photoelectric conversion devices in a hybrid photoelectric conversion device in which an amorphous silicon photoelectric conversion unit and a crystalline silicon photoelectric conversion unit are stacked in two stages. The fall of the current and the rise of the spectral sensitivity current of the crystalline silicon photoelectric conversion unit intersect at a wavelength near 600 nm. A film that reflects light in the vicinity of 600 nm well, that is, a film having a small refractive index for light of 600 nm is suitable for increasing the power generation current of the front photoelectric conversion unit. The refractive index can be evaluated using, for example, a spectroscopic ellipsometry method.

  On the other hand, by using a film having a high oxygen concentration in the film, the influence of the photoelectric conversion characteristics is reduced even after the atmospheric exposure process, which is a feature of the present invention. This is because, as already described, the silicon composite layer is an oxygen-containing film, so that the influence of surface alteration such as oxidation due to atmospheric exposure is small. Note that the oxygen concentration in the silicon composite layer can be analyzed by SIMS, ESCA, EPMA, Auger electron spectroscopy, etc. while changing the depth detected by wet etching, plasma etching, ion sputtering, or the like. .

  Moreover, it is preferable that the film thickness of the entire silicon composite layer be 20 nm or more and 130 nm or less because functions and effects as the intermediate reflection layer are increased.

  Thereafter, the substrate is introduced into the second plasma CVD apparatus, and one conductive type layer 41, a substantially intrinsic semiconductor photoelectric conversion layer 42 and a reverse conductive type layer 43 included in the rear photoelectric conversion unit 4 are sequentially formed by the plasma CVD method. Is deposited. Here, the first plasma CVD apparatus and the second plasma CVD apparatus may be the same apparatus, but separate apparatuses are more preferable in terms of increasing production efficiency.

  One conductivity type layer of the rear photoelectric conversion unit formed by the second plasma CVD apparatus is 0.01 to 0.8 times the power density / film forming pressure at the time of forming the silicon composite layer formed by the first CVD apparatus. By forming in a range, even if one conductivity type layer of the rear photoelectric conversion unit is formed immediately above the silicon composite layer, a good connection between the front photoelectric conversion unit and the rear photoelectric conversion unit is possible. When it exceeds 0.8 times, the silicon composite layer, the silicon composite layer that is the reverse conductivity type layer of the front photoelectric conversion unit, and the one conductivity type layer of the rear photoelectric conversion unit cannot be connected well. Further, when the power density / film forming pressure is less than 0.01 times, the crystallization of one conductivity type layer does not proceed sufficiently, and the performance of the rear photoelectric conversion unit is deteriorated.

  In addition, a low power density / film forming pressure is equivalent to a low film forming speed, and in terms of increasing production efficiency, one conductivity type layer of the rear photoelectric conversion unit is a reverse conductivity type of the front photoelectric conversion unit. More preferably, the layer is formed in the range of power density / film forming pressure of 0.1 to 0.8 times that of the silicon composite layer.

  The photoelectric conversion device shown in FIG. 1 is a relatively simple photoelectric conversion device in which two photoelectric conversion units 3 and 4 are stacked, but the present invention is a tandem photoelectric conversion device in which three or more photoelectric conversion units are stacked. Can also be applied. For example, in the three-stage stacked photoelectric conversion device arranged in the order of the first photoelectric conversion unit, the second photoelectric conversion unit, and the third photoelectric conversion unit from the light incident side, the first photoelectric conversion unit and the second photoelectric conversion unit are respectively Considering the front photoelectric conversion unit and the rear photoelectric conversion unit, a conductive silicon composite layer may be provided in the vicinity of the boundary between the two. Alternatively, the second photoelectric conversion unit and the third photoelectric conversion unit may be regarded as a front photoelectric conversion unit and a rear photoelectric conversion unit, respectively, and a conductive silicon composite layer may be provided in the vicinity of the boundary between them. Of course, a structure in which a silicon composite layer is provided both near the boundary between the first photoelectric conversion unit and the second photoelectric conversion unit and near the boundary between the second photoelectric conversion unit and the third photoelectric conversion unit may be used. As the three-stage stacked photoelectric conversion device, for example, the first photoelectric conversion unit is an amorphous silicon photoelectric conversion unit, the second photoelectric conversion unit is an amorphous silicon germanium or crystalline silicon-based photoelectric conversion unit, and a third photoelectric conversion unit. In the case of using amorphous silicon germanium or crystalline silicon photoelectric conversion unit, the combination is not limited to this.

  Furthermore, although the embodiment using a transparent substrate is shown in the example of FIG. 1, the present invention has a back electrode layer, a rear photoelectric conversion unit, a front photoelectric conversion unit, a transparent electrode layer on an arbitrary substrate including a non-transparent substrate. Can also be applied to stacked photoelectric conversion devices of the type in which light is incident from the opposite direction of the substrate, and the conductive silicon composite layer is intermediately reflected near the boundary between the rear and front photoelectric conversion units. Similar effects can be obtained by arranging the layers.

Note that the following parameters are used to explain the effects of the present invention. The following units are used in the “table” shown below.
Film forming pressure in CVD method (unit of Pa).
The dilution rate at the time of film formation in the CVD method is a value by which the silane gas at the time of film formation is diluted with hydrogen gas, and is a value obtained by dividing (dividing) the flow rate of H ₂ by SiH ₄ . For example, H ₂ / SiH ₄ = 300/1 is represented as 300. Although the silane gas may be written first and expressed, the meaning of the dilution ratio is the same, and (SiH ₄ / H ₂ = 1/300) is expressed as 300.
Power density in CVD method (unit of W / cm ² ).
The power density / film forming pressure is indicated by a value obtained by dividing (dividing) W / cm ² by Pa.

  In the following, as an example of a manufacturing method of a stacked photoelectric conversion device including a stacked structure corresponding to the above-described embodiment, two stacks in which an amorphous silicon photoelectric conversion unit and a crystalline silicon photoelectric conversion unit are stacked A stacked type superconducting photoelectric conversion device will be given and will be described in detail in comparison with a comparative example according to the prior art. In the drawings, the same members are denoted by the same reference numerals, and redundant description is omitted. Moreover, this invention is not limited to a following example, unless the meaning is exceeded.

  First, in Tables 1 and 2, the silicon composite layer, which is the reverse photoelectric type layer of the front photoelectric conversion unit, which is the main element of the comparative example and the embodiment using the present invention, is formed adjacent to this after exposure to the atmosphere. The main film forming conditions of one conductivity type layer of the rear photoelectric conversion unit are shown. Table 3 shows relative values of photoelectric conversion characteristics of the photoelectric conversion devices created using the comparative examples and the examples. A relative value is a relative value of each comparative example and example when Example 1 is set to 1.

(Comparative Example 1)
A stacked photoelectric conversion device similar to that shown in FIG. 1 was produced. First, the transparent electrode layer 2 containing SnO 2 as a main component was formed on the transparent glass substrate 1. Thereafter, the substrate with the transparent electrode layer is introduced into the first plasma CVD apparatus and heated, and then the p-type amorphous silicon carbide layer 31 and the i-type amorphous silicon in the amorphous silicon photoelectric conversion unit 3 are used. The photoelectric conversion layer 32 and the n-type silicon composite layer 33 were formed with thicknesses of 15 nm, 300 nm, and 50 nm, respectively.

The n-type silicon composite layer 33 was formed under the following conditions.
The flow rate ratio of the gas during film formation was SiH ₄ / CO ₂ / PH ₃ / H ₂ = ¼ / 0.028 / 300, and the film formation pressure was 850 Pa. The film was formed at a power frequency of 13.56 MHz, a power density of 111 mW / cm ² , and a substrate temperature of 180 ° C.
At this time, the refractive index of the n-type silicon composite layer 33 with respect to light of 600 nm was 2.0.

  After the film formation of the n-type silicon composite layer 33 was completed and evacuation was performed, the substrate 1 was immediately transferred to the unload chamber of the first plasma CVD apparatus, quickly filled with nitrogen gas, and taken out into the atmosphere. .

Then, after being left in the atmosphere for about 24 hours, in the second plasma CVD apparatus, the p-type microcrystalline silicon layer 41 of the crystalline silicon photoelectric conversion unit 4 which is the rear photoelectric conversion unit is formed at a gas flow rate ratio of SiH ₄ / B ₂ H ₆ / H ₂ = 1 / 0.0028 / 222, and the film forming pressure was 850 Pa. The film was formed at a power frequency of 13.56 MHz, a power density of 111 mW / cm ² , and a substrate temperature of 180 ° C.

  Thereafter, the non-doped i-type crystalline silicon photoelectric conversion layer 42 and the n-type microcrystalline silicon layer 43 are respectively formed at a thickness of 15 nm, 2.5 μm, and 15 nm without taking the substrate out of the second plasma CVD apparatus. Formed. Thereafter, Al-doped ZnO with a thickness of 90 nm and Ag with a thickness of 300 nm were sequentially formed as the back electrode layer 5 by sputtering.

  Through the above film formation process, a two-stack type stacked photoelectric conversion device in which an amorphous silicon unit and a crystalline silicon unit are stacked is formed. In order to complete the element of the photoelectric conversion device, it is necessary to perform other processes such as element separation and electrode extraction part formation, but since the contents are not directly related to the present invention, details are here. I will omit it.

  The results are summarized in Table 1.

The film formation pressure of the silicon composite layer is 850 Pa, and the dilution ratio (the gas flow rate ratio during film formation (SiH ₄ / H ₂ = 1/300) is represented by 300). The power density 111 mW / cm ² is 0. It is shown in the table at 111 W / cm ² . The power density / film forming pressure is a value obtained by dividing (dividing) 0.111 W / cm ² by 850 Pa, and is expressed as 0.111 / 850 = 0.001331 = 1.31E-4.
The p-type microcrystalline silicon layer 41 of the crystalline silicon photoelectric conversion unit 4 which is the rear photoelectric conversion unit has a film forming pressure of 850 Pa and a dilution ratio (a gas flow rate ratio during film formation (SiH ₄ / H ₂ = 1 / 222) is represented as 222.) The power density 111 mW / cm ² is represented in the table as 0.111 W / cm ² . The power density / film forming pressure is a value obtained by dividing (dividing) 0.111 W / cm ² by 850 Pa, and is expressed as 0.111 / 850 = 0.001331 = 1.31E-4.
In the following examples and comparative examples, the contents described in the tables are the same as described above.

In Table 2, (power density of rear one conductivity type layer / film formation pressure) / (power density of reverse reverse conductivity type layer / film formation pressure) means (power density of rear photoelectric conversion unit one conductivity type layer / The value obtained by dividing (dividing) the (film forming pressure) by (power density of the reverse photoelectric conversion layer of the front photoelectric conversion unit / film forming pressure).
The dilution ratio in Table 2 is (dilution ratio of the rear photoelectric conversion unit one conductivity type layer) / (dilution ratio of the front photoelectric conversion unit reverse conductivity type layer), that is, (dilution ratio of the rear photoelectric conversion unit one conductivity type layer). ) Is divided (divided) by (dilution ratio of the front photoelectric conversion unit reverse conductivity type layer).
In the following examples and comparative examples, the contents described in the tables are the same as described above.

V _oc listed in Table 3 is a relative value of the open-circuit voltage with the open-circuit voltage of Example 1 being 1. J _sc is a relative value of the short-circuit current density with the short-circuit current density of Example 1 being 1. FF is a relative value of the curvature factor with the curvature factor of Example 1 as 1. Eff is a relative value of the conversion efficiency with the conversion efficiency of Example 1 as 1.
In the following examples and comparative examples, the contents described in the tables are the same as described above.

Example 1
Similarly, the stacked photoelectric conversion device shown in FIG. 1 was produced. The difference from Comparative Example 1 is that the gas flow rate ratio during the formation of the n-type silicon composite layer 33 is SiH ₄ / CO ₂ / PH ₃ / H ₂ = 1 / 2.5 / 0.025 / 300, and the film forming pressure is The power density is 221 mW / cm ^{2 at} 750 Pa.
At this time, the refractive index of the n-type silicon composite layer 33 with respect to light of 600 nm was 2.0.

The difference from the embodiment of CO2 flow rate ratio, when changing the power density, in order to compensate for this because the optimum ratio of SiH ₄ and CO ₂ flow rate ratio is changed. Other than that, the manufacturing method is the same as that of Comparative Example 1, including the conditions for forming the p-type microcrystalline silicon layer 41 of the crystalline silicon photoelectric conversion unit 4 which is the rear photoelectric conversion unit.

In the photoelectric conversion devices manufactured in Comparative Example 1 and Example 1, photoelectric conversion characteristics were measured by irradiating AM1.5 light with a light amount of 100 mW / cm ² at 25 ° C. using a solar simulator. . Table 3 shows relative values when the photoelectric conversion efficiency of Example 1 is 1. When the conversion efficiency of Example 1 was 1, the relative value of the conversion efficiency of Comparative Example 1 was as large as 0.05, and the conversion efficiency was greatly reduced.

In Example 2, the flow rate ratio of gas at the time of forming the n-type silicon composite layer 3 is SiH ₄ / CO ₂ / PH ₃ / H ₂ = 1 / 2.2.6 / 0.013 / 300, and the film forming pressure is 750 Pa. It was. The film was formed at a power frequency of 27.12 MHz, a power density of 232 mW / cm ² , and a substrate temperature of 200 ° C. After the n-type silicon composite layer 33 is formed, it is quickly taken out into the atmosphere as in the first embodiment, and then exposed to the atmosphere for 24 hours or more in the same manner as in the first embodiment. Then, in the second plasma CVD apparatus, the rear photoelectric conversion unit 4 The p-type microcrystalline silicon layer 41 has a gas flow rate ratio of SiH ₄ / B ₂ H ₆ / H ₂ = 1 / 0.0029 / 225, a film forming pressure of 850 Pa, and a power supply frequency of 13.56 MHz. The film was formed at a power density of 89 mW / cm ² and a substrate temperature of 160 ° C.
The subsequent steps are the same as those in Example 1 including the photoelectric conversion performance measurement. Also in this case, good photoelectric conversion efficiency was obtained, and the same conversion efficiency as in Example 1 was obtained.

In Example 3, the formation conditions of the p-type microcrystalline silicon layer 41 of the rear photoelectric conversion unit 4 in the second plasma CVD apparatus of Example 2 are set, and the gas flow rate ratio during film formation is SiH ₄ / B ₂ H. _{The only difference is that 6} / H ₂ = 1 / 0.0031 / 194, the film forming pressure is 1200 Pa, the power frequency is 13.56 MHz, the power density is 89 mW / cm ² , and the substrate temperature is 160 ° C. Even in this case, the photoelectric conversion efficiency was the same as that in Example 1.

In Comparative Example 2, the film-forming pressure when forming the n-type silicon composite layer 3 in Example 2 was set to 1260 Pa, and the p-type microcrystalline silicon layer 41 of the rear photoelectric conversion unit 4 in the second plasma CVD apparatus was used. The formation conditions are as follows: the gas flow rate ratio during film formation is SiH ₄ / B ₂ H ₆ / H ₂ = 1 / 0.013 / 400, the film formation pressure is 1260 Pa, the power supply frequency is 13.56 MHz, and the power density is 185 mW / It is different in that it is cm ² . In this case, good photoelectric conversion efficiency was not obtained, and when the conversion efficiency of Examples 1, 2, and 3 was set to 1, the relative value of the conversion efficiency of Comparative Example 2 was as large as 0.04. A decline occurred.

  The difference between Comparative Examples 1 and 2 and Examples 1, 2 and 3 is that the formation conditions of the composite silicon layer, which is the reverse conductivity type layer of the front photoelectric conversion unit, and the one type conductivity layer of the rear photoelectric conversion unit are different. Mainly different parameters are the power density and the deposition pressure when forming the silicon composite layer.

  Table 2 shows the ratio of the reverse conductivity type silicon composite layer and the back photoelectric conversion unit one conductivity type layer power density / film forming pressure under the conditions used in each of the examples and comparative examples.

  In Comparative Example 1, the power density and the film forming pressure of the reverse conductivity type silicon composite layer adjacent to the air exposure surface and the back photoelectric conversion unit one conductivity type layer are the same. This is based on the concept of those skilled in the art that “the outermost layer exposed to the atmosphere and the layer formed immediately after exposure to the atmosphere are preferably formed under the same conditions”.

  On the other hand, in Examples 1, 2 and 3, the power density / film formation pressure of the reverse conductivity type silicon composite layer and the back photoelectric conversion unit one conductivity type layer adjacent to each other with the air exposure surface as a boundary are greatly changed. In this case, the pressure is set to reverse conductivity type silicon composite layer> rear photoelectric conversion unit one conductivity type layer.

  Comparative Example 2 is a case where the power density / film-forming pressure is set to the reverse conductive layer silicon composite layer> the rear photoelectric conversion unit one conductive type layer, while the rear photoelectric conversion unit one conductive type layer / the reverse conductive layer silicon composite. This is a case where the layer and the rear photoelectric conversion unit = about 0.8. Even in this case, good photoelectric conversion efficiency cannot be obtained.

Therefore, the reverse conductivity type silicon composite layer adjacent to the air exposure surface and the back photoelectric conversion unit one conductivity type layer have the same and close conditions (power density / film forming pressure ratio of about 0.8). ) That good photoelectric conversion efficiency cannot be obtained,
When the back photoelectric conversion unit is formed with one conductivity type layer at a power density / film forming pressure of 0.2 to 0.5 times that of the reverse conductivity type silicon composite layer, good photoelectric conversion efficiency can be obtained. I can tell you.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent electrode layer 3 The amorphous silicon photoelectric conversion unit 31 which is a front photoelectric conversion unit 31 The p-type amorphous silicon carbide layer 32 which is one conductivity type layer in a front photoelectric conversion unit in a front photoelectric conversion unit An i-type amorphous silicon photoelectric conversion layer 33 which is a photoelectric conversion layer, an n-type layer including a silicon composite layer which is a reverse conductivity type layer in the front photoelectric conversion unit, a crystalline silicon photoelectric conversion unit which is a rear photoelectric conversion unit 41 p-type layer 42 which is one conductivity type layer in the back photoelectric conversion unit, non-doped i-type crystalline photoelectric conversion layer 43 reverse conductivity type layer in the back photoelectric conversion unit, which is a photoelectric conversion layer in the back photoelectric conversion unit N-type layer 5 back electrode layer

Claims (2)

Seen from the light incident side
One conductivity type layer;
A reverse-conductivity type in a front photoelectric conversion unit that includes a plurality of photoelectric conversion units in which a substantially intrinsic semiconductor photoelectric conversion layer and a reverse-conductivity type layer are arranged in this order, and are relatively disposed on the light incident side. The layer is a method of manufacturing a stacked photoelectric conversion device which is a reverse conductivity type layer having at least a part of a silicon composite layer in which a silicon crystal phase is mixed in an amorphous alloy of silicon and oxygen. And forming a substantially intrinsic semiconductor photoelectric conversion layer and a reverse conductivity type layer by plasma CVD, respectively, and forming at least a silicon composite layer of the reverse conductivity type layer of the front photoelectric conversion unit. And a step immediately after that, the step of exposing the outermost surface of the silicon composite layer to the atmosphere by taking it out to the atmosphere once. A step of forming a mold layer, and a step of forming a crystalline one-conductivity-type layer of the rear photoelectric conversion unit is a power density / film forming pressure of a silicon composite layer of a reverse-conductivity type layer of the front photoelectric conversion unit A method of manufacturing a stacked photoelectric conversion device, characterized in that the power density is in a range of 0.01 times to less than 0.8 times the power density / film forming pressure in the step of forming the film. To hydrogen flow rate / SiH ₄ gas flow rate during the front photoelectric conversion unit opposite conductivity type silicon composite layer formed, hydrogen flow rate / SiH ₄ gas flow rate during one conductivity type layer formed in the rear unit formed thereon, 0 The method for producing a stacked photoelectric conversion device according to claim 1, comprising a step of being formed in a range of 1 to 1.2 times.

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