JP5136066B2 - Photovoltaic element and manufacturing method thereof - Google Patents

Description

  The present invention relates to a photovoltaic device and a manufacturing method thereof.

Conventionally, a solar cell including quantum dots in a power generation layer is known (Patent Document 1). This solar cell has a pin structure formed on a substrate. The p layer is made of p-type GaAs having an impurity concentration of 1 × 10 ¹⁸ cm ⁻³ . The i layer includes a base material of GaAs and quantum dots made of GaSb. The n layer is made of n-type GaAs having an impurity concentration of 1 × 10 ¹⁸ cm ⁻³ . The substrate is made of n-type GaAs having an impurity concentration of 1 × 10 ¹⁸ cm ⁻³ .

  This solar cell is formed by sequentially laminating n-type GaAs, GaAs / GaSb, and p-type GaAs on a substrate by MBE (Molecular Beam Epitaxy) method.

  This solar cell receives sunlight from the p-type GaAs side, absorbs light by the base material (GaAs) constituting the i layer and the quantum dots (GaSb) formed in the i layer, and generates electron-hole pairs. Generate.

  Since the energy band gap of GaSb is smaller than that of GaAs, quantum dots made of GaSb absorb light on the long wavelength side that cannot be absorbed by GaAs and generate electron-hole pairs.

Therefore, this solar cell can absorb more light than the case where the i layer is made of GaAs, and the conversion efficiency is improved.
JP 2006-114815 A

  However, since the solar cell described in Patent Document 1 is formed on a semiconductor substrate using the MBE method, there is a problem that it is difficult to reduce the manufacturing cost.

  Moreover, since i layer of the solar cell described in patent document 1 has a film thickness of 1-2.5 micrometers, there exists a problem that sunlight cannot fully be absorbed and conversion efficiency is low.

  Therefore, the present invention has been made to solve such a problem, and an object thereof is to provide a photovoltaic device that can be easily manufactured at low cost.

  Another object of the present invention is to provide a photovoltaic device capable of improving the conversion efficiency.

  Furthermore, another object of the present invention is to provide a method for manufacturing a photovoltaic device that can be easily manufactured at low cost.

  Furthermore, another object of the present invention is to provide a method for manufacturing a photovoltaic device capable of improving the conversion efficiency.

  According to this invention, the photovoltaic device includes a substrate, a first semiconductor layer, a second semiconductor layer, and a third semiconductor layer. The substrate is made of a material different from that of a semiconductor that converts light into electricity. The first semiconductor layer is formed on the substrate and has the first conductivity type. The second semiconductor layer is formed on the first semiconductor layer and converts light into electricity. The third semiconductor layer is formed on the second semiconductor layer and has a second conductivity type different from the first conductivity type. The second semiconductor layer includes an amorphous phase, a crystalline phase, and a substance that increases light absorption.

  Preferably, the second semiconductor layer includes a plurality of fourth semiconductor layers, a plurality of fifth semiconductor layers, n (n is a positive integer) number of sixth semiconductor layers, and m (m is a positive number). An integer) of light absorbing materials. The plurality of fourth semiconductor layers are made of an amorphous phase. The plurality of fifth semiconductor layers are made of a crystal phase. The n sixth semiconductor layers are formed in at least one fourth semiconductor layer of the plurality of fourth semiconductor layers, and each of the sixth semiconductor layers includes nano-sized crystal grains. The m light absorbing materials are coupled to at least one of the n sixth semiconductor layers, and each absorbs light having a wavelength in a predetermined range.

  Preferably, each of the plurality of fourth semiconductor layers is made of a porous amorphous phase.

  Preferably, the second semiconductor layer includes a plurality of fourth semiconductor layers, a plurality of fifth semiconductor layers, n (n is a positive integer) number of sixth semiconductor layers, and m (m is a positive number). An integer) of light absorbing materials. The plurality of fourth semiconductor layers are made of an amorphous phase. The plurality of fifth semiconductor layers are made of a crystal phase. The n sixth semiconductor layers are arranged around at least one of the plurality of fifth semiconductor layers, and each of the sixth semiconductor layers includes nano-sized crystal grains. The m light absorbing materials are coupled to at least one of the n sixth semiconductor layers, and each absorbs light having a wavelength in a predetermined range.

  Preferably, each of the m light absorbing materials is made of a metal complex or an organic dye molecule.

  Preferably, each of the plurality of fifth semiconductor layers has one end contacting one of the first and third semiconductor layers and the other end contacting one of the first and third semiconductor layers. The columnar structure is formed in contact with and extends in the direction from the first semiconductor layer to the third semiconductor layer.

  According to the invention, in the method of manufacturing a photovoltaic device, the first semiconductor layer having the first conductivity type is formed on a substrate made of a material different from that of a semiconductor that converts light into electricity. And a second step of forming a second semiconductor layer on the first semiconductor layer including a substance that converts light into electricity and increases an amorphous phase, a crystalline phase, and a light absorption amount; And a third step of forming a third semiconductor layer having a second conductivity type different from the first conductivity type on the second semiconductor layer.

  Preferably, the second semiconductor layer includes a plurality of fourth semiconductor layers, a plurality of fifth semiconductor layers, n (n is a positive integer) number of sixth semiconductor layers, and m (m is a positive number). An integer) of light absorbing materials. The plurality of fourth semiconductor layers are made of an amorphous phase. The plurality of fifth semiconductor layers are made of a crystal phase. The n sixth semiconductor layers are formed in at least one fourth semiconductor layer of the plurality of fourth semiconductor layers, and each of the sixth semiconductor layers includes nano-sized crystal grains. The m light absorbing materials are coupled to at least one of the n sixth semiconductor layers, and each absorbs light having a wavelength in a predetermined range. The second step of the photovoltaic device manufacturing method includes a first sub-step of forming a plurality of crystal nuclei on the first semiconductor layer, and a plurality of fourth semiconductor layers on the plurality of crystal nuclei. A second sub-step for forming a plurality of fourth semiconductor layers, a plurality of fifth semiconductor layers, and n sixth semiconductor layers, and a second sub-step for forming m light-absorbing substances. 3 sub-steps.

  Preferably, the second sub-step includes a step A for depositing the fourth and fifth semiconductor layers under a condition that an amorphous phase is formed, a step B for depositing the sixth semiconductor layer, a step A and a step And step C that repeatedly executes B a predetermined number of times.

  Preferably, the second semiconductor layer includes a plurality of fourth semiconductor layers, a plurality of fifth semiconductor layers, n (n is a positive integer) number of sixth semiconductor layers, and m (m is a positive number). An integer) of light absorbing materials. The plurality of fourth semiconductor layers are made of an amorphous phase. The plurality of fifth semiconductor layers are made of a crystal phase. The n sixth semiconductor layers are formed in at least one fourth semiconductor layer of the plurality of fourth semiconductor layers, and each of the sixth semiconductor layers includes nano-sized crystal grains. The m light absorbing materials are coupled to at least one of the n sixth semiconductor layers, and each absorbs light having a wavelength in a predetermined range. The second step of the photovoltaic device manufacturing method includes a first sub-step of forming a plurality of crystal nuclei on the first semiconductor layer, and a plurality of fourth semiconductor layers on the plurality of crystal nuclei. A second sub-step of forming a plurality of fourth semiconductor layers and a plurality of fifth semiconductor layers, a third sub-step of making the plurality of fourth semiconductor layers porous, and porous And a fourth sub-step of forming m light-absorbing substances in the fourth semiconductor layer.

  In the present invention, the photovoltaic element has a structure in which first to third semiconductor layers are formed on a substrate made of a material different from that of a semiconductor that converts light into electricity. The second semiconductor layer that converts light into electricity includes an amorphous phase, a crystalline phase, and a structure that increases light absorption.

  Therefore, according to this invention, the manufacturing cost of a photovoltaic device can be reduced.

  In addition, since the second semiconductor layer that converts light into electricity includes an amorphous phase, a crystalline phase, and a structure that increases the amount of light absorption, it absorbs more incident light and absorbs electrons and holes. And improves the transport properties of the photogenerated electrons and holes.

  Therefore, according to the present invention, the conversion efficiency of the photovoltaic element can be improved.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view of a photovoltaic element according to Embodiment 1 of the present invention. Referring to FIG. 1, a photovoltaic element 10 according to Embodiment 1 of the present invention includes an insulating substrate 1, a transparent conductive film 2, a p layer 3, an i layer 4, an n layer 5, and an electrode 6. With.

  The transparent conductive film 2 is formed on one main surface of the insulating substrate 1. The p layer 3 is formed in contact with the transparent conductive film 2. The i layer 4 is formed in contact with the p layer 3. N layer 5 is formed in contact with i layer 4. The electrode 6 is formed in contact with the n layer 5.

  The insulating substrate 1 is made of glass, for example. The transparent conductive film 2 is made of, for example, ITO (Indium Tin Oxide) and has a thickness in the range of 500 nm to 1000 nm. The p layer 3 is made of, for example, p-type hydrogenated amorphous silicon (p-type a-Si: H) and has a thickness of 10 nm.

  The i layer 4 has a film thickness of 300 nm to 1000 nm, and includes a plurality of amorphous thin films 41 and a plurality of crystal thin films 42. The plurality of amorphous thin films 41 and the plurality of crystal thin films 42 are stacked in the direction from the p layer 3 to the n layer 5 so that the amorphous thin films 41 and the crystal thin films 42 are in contact with each other.

  The amorphous thin film 41 has a film thickness in the range of, for example, 2 to 10 nm, and the nano-sized crystal grains 411 and the light absorbing material 412 are in i-type hydrogenated amorphous silicon (i-type a-Si: H). It consists of the structure included. The light absorbing material 412 is made of a metal complex or an organic dye molecule, and is bonded to the crystal grains 411. Specific examples of the metal complex are Mg-phthalocyanine or Ru-terpyridine, and a specific example of the organic dye molecule is merocyanine.

  Since the crystal grain 411 has a nanosize, the amorphous thin film 41 absorbs light having energy corresponding to the energy difference between the phonon in the crystal grain 411 and the phonon in the a-Si: H by the nanosize effect. And contribute to power generation. The light absorbing material 412 has a level in the forbidden band in a-Si: H, and has a wavelength that cannot be absorbed by a-Si: H constituting the amorphous thin film 41 (for example, from about 730 nm). Light having a wavelength in the range of about 800 nm) and generate electrons and holes that contribute to power generation. That is, the amorphous thin film 41 absorbs light having a wavelength that cannot be absorbed by a-Si: H and contributes to power generation. Therefore, the crystal grains 411 and the light absorbing material 412 are materials that increase the amount of light absorption.

  The crystal thin film 42 is made of i-type polycrystalline Si (i-type poly-Si) and has a thickness in the range of 2 to 10 nm.

  The n layer 5 is made of n-type hydrogenated amorphous silicon (n-type a-Si: H) and has a thickness of 20 nm. The electrode 6 is made of, for example, aluminum (Al).

  The photovoltaic element 10 receives light Lgt from the p layer 3 side, and converts the received light Lgt into electricity.

  FIG. 2 is a schematic sectional view of a plasma CVD (Chemical Vapor Deposition) apparatus. Referring to FIG. 2, plasma CVD apparatus 100 includes reaction chamber 110, transfer chamber 120, antennas 130 and 140, gas supply pipes 150 and 160, support base 170, arm 180, heater 190, A high-frequency power source 200.

  The reaction chamber 110 has a hollow cylindrical shape and has an inner diameter of 450 mmφ. The reaction chamber 110 has an exhaust pipe 111 on the side wall 110A. Moreover, the reaction chamber 110 has a hole (not shown) through which the support base 170 can pass on the bottom surface 110B. The exhaust pipe 111 has one end connected to the reaction chamber 110 and the other end connected to an exhaust device (not shown). The exhaust device includes a turbo molecular pump and a rotary pump.

  The transfer chamber 120 has a hollow cylindrical shape and is disposed in contact with the bottom surface 110 </ b> B of the reaction chamber 110. The transfer chamber 120 has an open / close door 121 on the side wall 120A.

  The antennas 130 and 140 pass through the upper surface 110C of the reaction chamber 110, and are fixed to the reaction chamber 110 so that one end thereof is in contact with the upper surface 110C of the reaction chamber 110. A part of the antennas 130 and 140 disposed in the reaction chamber 110 is curved in a substantially arc shape.

  The gas supply pipes 150 and 160 are pipes having a diameter of ¼ inch φ, one end connected to the upper surface 110C of the reaction chamber 110, and the other end connected to a gas cylinder (not shown).

  The support base 170 has a substantially disk shape and is fixed to one end of the arm 180. When the bottom surface of the support table 170 is in contact with the bottom surface 110B of the reaction chamber 110, the distance between the upper surface 110C of the reaction chamber 110 and the support table 170 is 400 mm.

  The arm 180 is disposed in the transfer chamber 120. The heater 190 is disposed inside the support base 170. The high frequency power source 200 is connected to the antennas 130 and 140.

  The exhaust pipe 111 exhausts the gas in the reaction chamber 110. The opening / closing door 121 is opened and closed by an operator of the plasma CVD apparatus 100.

The gas supply pipes 150 and 160 supply the source gas from the gas cylinder into the reaction chamber 110. More specifically, when the p-layer 3 is formed, the gas supply pipes 150 and 160 are made of 5% diborane (B ₂ ) diluted with silane (SiH ₄ ) gas, hydrogen (H ₂ ) gas, and H ₂ gas. H ₆ ) A gas is supplied from the gas cylinder into the reaction chamber 110. The gas supply pipes 150 and 160 supply SiH ₄ gas and H ₂ gas from the gas cylinder into the reaction chamber 110 when the i layer 4 is formed. Further, when the n layer 5 is formed, the gas supply pipes 150 and 160 are configured to supply SiH ₄ gas, H ₂ gas, and 5% phosphine (PH ₃ ) gas diluted with H ₂ gas from the gas cylinder into the reaction chamber 110. Supply.

  The support stand 170 supports the sample 300. The arm 180 moves the support base 170 in the vertical direction DR1 between the bottom surface 110B of the reaction chamber 110 and the bottom surface 120 of the transfer chamber 120. The heater 190 heats the sample 300. The high frequency power source 200 applies high frequency power of 13.56 MHz to the antennas 130 and 140.

  FIG. 3 is a plan view of the plasma CVD apparatus 100 viewed from the direction A shown in FIG. Referring to FIG. 3, antennas 130 and 140 and gas supply pipes 150 and 160 are arranged such that a line segment connecting antennas 130 and 140 is orthogonal to a line segment connecting gas supply pipes 150 and 160. The antennas 130 and 140 and the gas supply pipes 150 and 160 are disposed at a distance L1 from the side wall 110A of the reaction chamber 110. In this case, the distance L1 is set to 100 to 200 mm.

  The distance L2 between the antennas 130 and 140 and the gas supply pipes 150 and 160 is set to 100 mm or more.

  The antennas 130 and 140 have a length of 100 mm in the plan view shown in FIG. Therefore, the antennas 130 and 140 are curved along a circle having a diameter of 100 mm in the reaction chamber 110.

  In the plasma CVD apparatus 100, the high frequency power source 200 applies high frequency power to the antennas 130 and 140, so that a high frequency current flows through the antennas 130 and 140. In addition, a high-frequency electric field is generated by the generated high-frequency magnetic field. Then, plasma is generated around the antennas 130 and 140 by the high frequency magnetic field and the high frequency electric field.

  Thus, in the plasma CVD apparatus 100, a high frequency magnetic field and a high frequency electric field are induced by flowing a high frequency current through the curved antennas 130 and 140, and plasma is generated by the induced high frequency magnetic field and high frequency electric field. The plasma CVD apparatus 100 is an inductively coupled plasma (ICP) CVD apparatus.

  An operation of forming a thin film using the plasma CVD apparatus 100 will be described. When the operation of forming the thin film is started, the arm 180 moves downward so that the bottom surface of the support base 170 contacts the bottom surface 120B of the transfer chamber 120, and the door 121 is opened. Then, the sample 300 is placed on the support base 170 via the opening / closing door 121, and the opening / closing door 121 is closed.

  Thereafter, the arm 180 moves upward so that the bottom surface of the support base 170 contacts the bottom surface 110 </ b> B of the reaction chamber 110. Then, the inside of the reaction chamber 110 is evacuated through the exhaust pipe 111. The heater 190 heats the sample 300 to a predetermined temperature.

Then, the gas supply pipes 150 and 160 supply SiH ₄ gas or the like into the reaction chamber 110 from the gas cylinder. Thereby, the pressure in the reaction chamber 110 is set to a predetermined pressure. The high frequency power supply 200 applies predetermined high frequency power to the antennas 130 and 140. As a result, plasma is generated around the antennas 130 and 140, and a thin film is deposited on the sample 300.

  FIGS. 4 and 5 are first and second process diagrams respectively showing manufacturing steps of the photovoltaic element 10 shown in FIG. When the production of the photovoltaic element 10 is started, the insulating substrate 1 on which the transparent conductive film 2 is formed is cleaned and placed on the support base 170 of the plasma CVD apparatus 100 (see FIG. 4A). ).

  Then, the reaction chamber 110 is evacuated, and when the pressure in the reaction chamber 110 reaches a predetermined ultimate pressure, the p layer 3, the i layer 4, and the n layer 5 are made transparent conductive using the formation conditions shown in Table 1. Sequentially formed on the film 2.

  Hereinafter, formation of the p layer 3, the i layer 4, and the n layer 5 will be described in detail.

When the p-layer 3 is formed, the gas supply pipes 150 and 160 are provided with 5 to 10 sccm of SiH ₄ gas, 27 sccm of H ₂ gas and 0.5 sccm of 5% B ₂ H ₆ gas from the gas cylinder into the reaction chamber 110. Supply.

  Thereafter, the heater 190 heats the temperature of the insulating substrate 1 to 200 ° C., and the high frequency power source 200 applies high frequency power of 0.5 to 1.0 kW to the antennas 130 and 140. The high-frequency power supply 200 stops applying high-frequency power to the antennas 130 and 140 after one minute has elapsed since the start of applying high-frequency power to the antennas 130 and 140. Thereby, the p layer 3 is formed on the transparent conductive film 2 (see FIG. 4B).

Thereafter, the gas supply pipes 150 and 160 stop supplying 5% B ₂ H ₆ gas, and supply 5 to 10 sccm of SiH ₄ gas and 27 sccm of H ₂ gas into the reaction chamber 110. Then, the high frequency power source 200 applies 2.0 kW of high frequency power to the antennas 130 and 140 for 10 minutes. As a result, an amorphous thin film 41 of the i layer 4 is formed on the p layer 3 (see FIG. 4C).

Thereafter, the gas supply pipes 130 and 140 supply 3.6 sccm of SiH ₄ gas and 27 sccm of H ₂ gas into the reaction chamber 110, and the high-frequency power source 200 supplies 3.0 kW of high-frequency power for 10 minutes to the antenna 130. , 140. As a result, the crystal thin film 42 of the i layer 4 is formed on the amorphous thin film 41 (see FIG. 4D).

  Thereafter, the steps (c) and (d) described above are repeatedly performed until the film thickness of the i layer 4 reaches 300 nm to 1000 nm. As a result, a plurality of amorphous thin films 41 and a plurality of crystal thin films 42 are formed on the p layer 3 (see FIG. 4E).

  Then, the sample is taken out from the plasma CVD apparatus 100, and the taken-out sample is immersed in a solution containing a metal complex or an organic dye molecule to perform anodization, and a light absorbing material 412 made of the metal complex or the organic dye molecule. Are formed around the crystal grains 411. As a result, the i layer 4 is formed on the p layer 3 (see FIG. 5F).

Thereafter, the sample is set in the plasma CVD apparatus 100 again. The gas supply pipes 150 and 160 supply 5 to 10 sccm of SiH ₄ gas, 27 sccm of H ₂ gas, and 1 sccm of 5% PH ₃ gas into the reaction chamber 110, and the high-frequency power source 200 is 0.5 to 1 A high frequency power of 0.0 kW is applied to the antennas 130 and 140 for 1 minute. As a result, the n layer 5 is formed on the i layer 4 (see FIG. 5G).

  Then, the sample is taken out from the plasma CVD apparatus 100, and Al is formed on the n layer 5 using a vapor deposition apparatus. Thus, the photovoltaic element 10 is completed (see (h) in FIG. 5).

  FIG. 6 is an energy band diagram of the photovoltaic element 10 shown in FIG. Although the amorphous thin film 41 of the i layer 4 includes crystal grains 411, the energy band gap of the amorphous thin film 41 is mainly determined by a-Si: H. -Indicates the energy band gap of Si: H.

Referring to FIG. 6, E _cp represents the conduction band of p layer 3, E _vp represents the valence band of p layer 3, E _cn represents the conduction band of n layer 5, and E _vn represents represents the valence band of the n layer 5, E _F represents the Fermi level.

Since the p layer 3 is made of p-type a-Si: H, it has a band gap E _gp of about 1.7 eV, and the n layer 5 is made of n-type a-Si: H, so that it is about 1.7 eV. It has a band gap E _gn . Further, since the amorphous thin film 41 of the i layer 4 is mainly made of i-type a-Si: H, it has a band gap E _gi 1 of about 1.7 eV, and the crystal thin film 42 is made of i-type poly-Si. Therefore, it has a band gap E _gi 2 of 1.1 eV. Further, since the amorphous thin film 41 includes the light absorbing material 412, the level LV formed by the light absorbing material 412 is included in the forbidden band. The gap E _gi 3 from the level LV to the conduction band edge of the amorphous thin film 41 is about 1.5 eV.

As a result, the i layer 4 has a band gap E _gi that periodically changes from the p layer 3 to the n layer 5. Since the i layer 4 is sandwiched between the p layer 3 and the n layer 5, the conduction band and valence band of the i layer 4 are inclined between the p layer 3 and the n layer 5.

  The amorphous thin film 41 absorbs light having energy of 1.7 eV or more, that is, light having a wavelength shorter than about 730 nm, and light having energy smaller than 1.7 eV (range of about 730 nm to about 800 nm). Of light having a long wavelength) to generate electron-hole pairs. The crystalline thin film 42 absorbs light having energy of 1.1 eV or more, that is, light having a wavelength shorter than about 1130 nm, and generates electron-hole pairs.

  The electron-hole pairs generated in the amorphous thin film 41 are separated by the electric field existing in the i layer 4, the electrons move to the n layer 5 side, and the holes move to the p layer 3 side. . In addition, the electron-hole pairs generated in the crystal thin film 42 are also separated by the electric field present in the i layer 4, the electrons move to the n layer 5 side through the amorphous thin film 41, and the holes are Then, it moves to the p-layer 3 side through the amorphous thin film 41. In the i layer 4, an electric field exists, and the i-type a-Si: H constituting the amorphous thin film 41 has many levels in the forbidden band. And holes can move to the n-layer 5 side or the p-layer 3 side through levels in the forbidden band of i-type a-Si: H.

  As a result, the electron-hole pairs generated in the amorphous thin film 41 and the crystalline thin film 42 are separated to the n layer 5 side and the p layer 3 side, respectively, and contribute to power generation.

  In general, since a-Si: H has a light absorption coefficient that is about an order of magnitude larger than that of poly-Si, most electron-hole pairs are generated in the amorphous thin film 41 and contribute to power generation. The electrons and holes generated in the amorphous thin film 41 pass through the thinner a-Si: H region than when the entire region of the i layer is composed of a-Si: H. Since it moves to the layer 5 side and the p layer 3 side, the proportion of the generated electron-hole pairs contributing to power generation is higher than when the entire region of the i layer is composed of a-Si: H. .

  Further, in the photovoltaic element 10, electron-hole pairs are generated in the crystal thin film 42, and the generated electron-hole pairs contribute to power generation. It can contribute to power generation by absorbing light having a longer wavelength than when the region is made of a-Si: H.

  Therefore, the photovoltaic device 10 can improve the conversion efficiency as compared with the case where the entire region of the i layer is made of a-Si: H.

  Since the photovoltaic element 10 can be formed on the insulating substrate 1 such as glass as described above, the cost can be easily reduced.

  FIG. 7 is a schematic cross-sectional view of another photovoltaic element according to the first embodiment. The photovoltaic element according to Embodiment 1 may be the photovoltaic element 10A shown in FIG. Referring to FIG. 7, a photovoltaic element 10 </ b> A is obtained by replacing the substrate 1 of the photovoltaic element 10 shown in FIG. 1 with the substrate 11 and replacing the transparent conductive film 2 with the transparent conductive film 12. This is the same as the photovoltaic element 10.

  The board | substrate 11 consists of materials other than semiconductors, such as glass, a plastic film, and stainless steel. The transparent conductive film 12 is made of, for example, ITO and is formed on the p layer 3.

  In the photovoltaic element 10A, the substrate 11 is prepared in the step (a) shown in FIG. 4, and the n layer 5 is formed on the substrate 11 in the step (b) shown in FIG. In steps (c) to (f) shown in FIG. 5, the i layer 4 is formed on the n layer 5, and in the step (g) shown in FIG. 5, the p layer 3 is formed on the i layer 4 and shown in FIG. In (h), the transparent conductive film 12 is manufactured according to a process in which the transparent conductive film 12 is formed on the p layer 3 by sputtering.

  In the above description, it has been described that the p layer 3 and the n layer 5 of the photovoltaic elements 10 and 10A are made of a-Si: H. However, the present invention is not limited to this, and the photovoltaic elements 10 and 10A The p layer 3 and the n layer 5 may be made of poly-Si. In this case, p-type poly-Si and n-type poly-Si are formed using the conditions shown in Table 2.

  The p layer 3 and the n layer 5 of the photovoltaic elements 10 and 10A are made of a-Si such as hydrogenated amorphous silicon carbide (a-SiC: H) and hydrogenated amorphous silicon nitride (a-SiN: H). : It may be made of a material having a band gap larger than H.

When the p-layer 3 and the n-layer 5 are made of a-SiC: H, the p-layer 3 and the n-layer 5 are formed by forming conditions in which the flow rate of methane (CH ₄ ) gas is added to the forming conditions shown in Table 1. . In addition, when the p layer 3 and the n layer 5 are made of a-SiN: H, the p layer 3 and the n layer 5 are formed under the formation conditions in which the flow rate of ammonia (NH ₃ ) gas is added to the formation conditions shown in Table 1. Is done.

  In the above description, the photovoltaic elements 10 and 10A have been described as having a structure in which the p layer 3 is in contact with the transparent conductive films 2 and 12. However, in the present invention, the photovoltaic elements are not limited thereto. 10 and 10A may have a structure in which the n layer 5 is in contact with the transparent conductive films 2 and 12.

  Further, in the above description, it has been described that the crystal grains 411 and the light absorbing material 412 are formed on all of the plurality of amorphous thin films 41. The material 412 may be formed on at least one amorphous thin film 41 of the plurality of amorphous thin films 41.

  The number of crystal grains 411 formed on at least one amorphous thin film 41 of the plurality of amorphous thin films 41 may be n (n is a positive integer), and the number of crystal grains 411 may be one. The number of light absorbing materials 412 to be combined may be m (m is a positive integer).

[Embodiment 2]
FIG. 8 is a schematic cross-sectional view of the photovoltaic element according to the second embodiment. Referring to FIG. 8, the photovoltaic element 10B according to the second embodiment is obtained by replacing the i layer 4 of the photovoltaic element 10 shown in FIG. 1 with the i layer 40, and the others are photovoltaic elements. 10 is the same.

  i layer 40 is arranged between p layer 3 and n layer 5 in contact with p layer 3 and n layer 5. And i layer 40 has a film thickness of 300-1000 nm.

  The i layer 40 includes a plurality of amorphous regions 401 and a plurality of crystal regions 402. The plurality of amorphous regions 401 and the plurality of crystal regions 402 are arranged so that the amorphous regions 401 and the crystal regions 402 are in contact with each other in the in-plane direction of the insulating substrate 1. Each of the plurality of amorphous regions 401 and each of the plurality of crystal regions 402 has one end in contact with p layer 3 and the other end in contact with n layer 5.

  The amorphous region 401 has a width W1 of 10 to 20 nm, and has a structure in which crystal grains 411 and a light absorbing material 412 are formed in i-type a-Si: H. The crystal region 402 is made of i-type poly-Si and has a width W2 of 10 to 20 nm.

  FIGS. 9 and 10 are first and second process diagrams respectively showing manufacturing steps of the photovoltaic element 10B shown in FIG. Referring to FIG. 9, photovoltaic element 10 </ b> B is manufactured using the formation conditions shown in Table 3.

  More specifically, the photovoltaic element 10B is manufactured as follows. When the production of the photovoltaic element 10B is started, the steps (a) and (b) described above are sequentially performed using the plasma CVD apparatus 100, and the p layer 3 is formed on the transparent conductive film 2 of the insulating substrate 1. It is formed.

  Thereafter, the base layer 401 </ b> A is formed on the p-layer 3 using the uppermost formation conditions of the i-layer in Table 3. The underlayer 401A has a thickness of 10 to 20 nm and has a structure in which a plurality of crystal nuclei 413 made of Si are formed in i-type a-Si: H (see (c1) in FIG. 9).

In this case, the base layer 401A is formed using a forming condition in which the dilution ratio of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )) is in the range of 15.6% to 27.0%. Is done.

When 10 minutes have elapsed from the start of the formation of the base layer 401A, 5 to 10 sccm of SiH ₄ gas and 27 sccm of H ₂ gas are continuously supplied to the reaction chamber 110 from the gas supply pipes 150 and 160 and applied to the antennas 130 and 140. The high frequency power is reduced from 3.0 kW to 0.5 to 1.0 kW, and a thin film is grown on the base layer 401A for 10 minutes (see the middle stage of the i layer in Table 3). That is, a thin film is deposited on the base layer 401A under the condition that a-Si: H is formed. Thus, a thin film 4011 including a part of the amorphous region 401 and a part of the crystal region 402 is formed on the base layer 401A (see (d1) in FIG. 9).

Thereafter, the high frequency power applied to the antennas 130 and 140 is increased from 0.5 to 1.0 kW to 2.0 kW while maintaining the flow rates of SiH ₄ gas and H ₂ gas, and a thin film is deposited (i in Table 3). See bottom of layer). Thus, a thin film 4012 including crystal grains 411 is formed (see (e1) in FIG. 9).

  Then, steps (d1) and (e1) shown in FIG. 9 are repeatedly executed until the total film thickness reaches 300 to 1000 nm, and an i layer including an amorphous region 401 including crystal grains 411 and a crystal region 402 is formed. 40 is formed on the p-layer 3 (see (f1) in FIG. 10).

  After that, the sample is taken out from the plasma CVD apparatus 100, and the taken-out sample is immersed in a solution containing a metal complex or an organic dye molecule to perform anodization, and the light absorbing material 412 made of the metal complex or the organic dye molecule is crystal grains 411. To join. As a result, the i layer 40 is formed on the p layer 3 (see (g1) in FIG. 10).

Then, the sample is set in the plasma CVD apparatus 100 again. The gas supply pipes 150 and 160 supply 5 to 10 sccm of SiH ₄ gas, 27 sccm of H ₂ gas and 1 sccm of 5% PH ₃ gas into the reaction chamber 110, and the high-frequency power source 200 has 0.5 to 1.0 kW. Are applied to the antennas 130 and 140 for 1 minute. As a result, the n layer 5 is formed on the i layer 40.

  Then, the sample is taken out from the plasma CVD apparatus 100, and Al is formed on the n layer 5 using a vapor deposition apparatus. Thus, the photovoltaic element 10B is completed (see (h1) in FIG. 10).

In the above, the i layer 40 is formed by setting the dilution rate of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )) in the range of 15.6% to 27.0%. In the present invention, the i layer 40 is not limited to this, but generally, the i layer 40 has a dilution ratio of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )). It is set to a value of 50% or less.

When the i layer 40 having a relatively large number of crystal regions 402 is formed, the dilution rate of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )) is relatively high. When the i layer 40 is formed with a relatively small number of crystal regions 402, the dilution ratio of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )) is relatively low. Is set.

When the dilution ratio of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )) is relatively high, a plurality of crystal nuclei 413 having a relatively small size and a relatively high density are obtained. A plurality of crystals that are formed and have a relatively low size and a relatively low density when the dilution ratio of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )) is relatively low. This is because the nucleus 413 is formed.

As described above, in the present invention, by controlling the dilution rate of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ ), the amorphous material including crystal grains 411 and light absorbing material 412 is obtained. The i layer 40 including the region 401 and a plurality of crystal regions 402 grown in a columnar shape in a direction substantially perpendicular to the insulating substrate 1 is formed.

  FIG. 11 is an energy band diagram in the in-plane direction of the insulating substrate 1 of the i layer 40 shown in FIG. Note that although the amorphous region 401 of the i layer 40 includes crystal grains 411 and a light absorbing material 412, the energy band gap of the amorphous region 401 is mainly determined by a-Si: H. 8 shows the energy band gap of a-Si: H.

Referring to FIG. 11, amorphous region 401 is mainly made of i-type a-Si: H, and thus has an E _gi 1 band gap, and crystal region 402 is made of i-type poly-Si. , Having a band gap E _gi 2 smaller than the band gap E _gi 1. In addition, since the amorphous region 401 includes the light absorption material 412, the level LV formed by the light absorption material 412 is included in the forbidden band. The gap E _gi 3 from the level LV to the conduction band edge of the amorphous region 401 is about 1.5 eV.

  Therefore, in the i layer 40 of the photovoltaic element 10B, the energy levels of the conduction band and the valence band periodically change in the in-plane direction of the insulating substrate 1.

  Since the i layer 40 is sandwiched between the p layer 3 and the n layer 5, the amorphous region 401 and the crystal region 402 are, for example, in the direction from the near side to the far side on the paper surface of FIG. There is an electric field.

The amorphous region 401 absorbs light having an energy larger than the band gap E _gi 1 out of incident light incident on the photovoltaic device 10B, and is formed in the forbidden band of a-Si: H. The level LV absorbs light having energy smaller than the band gap E _gi 1 (light having a wavelength up to 800 nm) and generates an electron-hole pair. Then, electrons and holes generated in the amorphous region 401 move to the crystal region 402.

  The crystal region 402 also absorbs incident light incident on the photovoltaic element 10B, and generates electron-hole pairs.

  As a result, electrons and holes generated in the amorphous region 401 and the crystal region 402 move in the crystal region 402 by an electric field applied to the crystal region 402. More specifically, electrons generated in the amorphous region 401 and the crystal region 402 are moved from the p layer 3 side to the n layer 5 side by an electric field applied to the crystal region 402, and the amorphous region 401 and The holes generated in the crystal region 402 are moved from the n layer 5 side to the p layer 3 side by the electric field applied to the crystal region 402.

  Since the plurality of crystal regions 402 are in contact with both the p layer 3 and the n layer 5, most of the electrons and holes generated in the i layer 40 are not recombined, respectively. And reaches the p-layer 3 and contributes to power generation.

  As described above, i-type a-Si: H constituting the amorphous region 401 has a light absorption coefficient larger than that of i-type poly-Si constituting the crystalline region 402, and the amorphous region 401 is composed of crystal grains. 411 and the light absorbing material 412, in the photovoltaic element 10B, the amorphous region 401 mainly serves to absorb light and generate electron-hole pairs, and the crystal region 402 includes Mainly, it plays a role of causing photogenerated electrons and holes to travel to the n layer 5 side and the p layer 3 side while suppressing recombination, respectively.

  As a result, the photogenerated electrons and holes are difficult to recombine, and the conversion efficiency is improved.

  In addition, the electrons and holes generated in the amorphous region 401 do not necessarily move to the same crystal region 402. As shown in FIG. In some cases, the holes move to the crystal region 402 arranged on one side of 401, and the holes generated in the amorphous region 401 move to the crystal region 402 arranged on the other side of the amorphous region 401. As a result, the electrons and holes generated in the amorphous region 401 are spatially separated in the in-plane direction of the insulating substrate 1, and thus are difficult to recombine. Therefore, in the photovoltaic device 10B, the ratio of the photogenerated electrons and holes contributing to power generation is increased, and the conversion efficiency of the photovoltaic device 10B can be improved.

  In the photovoltaic element 10B, electrons and holes generated in the amorphous region 401 are moved in the amorphous region 401 to the n layer 5 side and the p layer 3 side by an electric field existing in the i layer 40, respectively. Sometimes it moves and contributes to power generation.

  FIG. 12 is a schematic cross-sectional view of another photovoltaic element according to the second embodiment. The photovoltaic element according to Embodiment 2 may be the photovoltaic element 10C shown in FIG. Referring to FIG. 12, photovoltaic element 10C is the same as photovoltaic element 10B except that i layer 40 of photovoltaic element 10B shown in FIG. 8 is replaced by i layer 40A. .

  The i layer 40A is obtained by replacing the amorphous region 401, the crystal grain 411, and the light absorbing material 412 of the i layer 40 shown in FIG. 8 with the amorphous region 403, the crystal grain 414, and the light absorbing material 415, respectively. Others are the same as the i layer 40.

  The amorphous region 403 is made of porous silicon. The crystal grain 414 is made of nano-sized crystalline silicon and is formed at the interface between the amorphous region 403 and the crystalline region 402. The light absorbing material 415 is made of the same material as the light absorbing material 412 described above, and is bonded around the crystal grains 414.

  FIGS. 13 and 14 are first and second process diagrams respectively showing manufacturing steps of the photovoltaic element 10C shown in FIG.

  Referring to FIG. 13, photovoltaic element 10 </ b> C is manufactured using the formation conditions shown in Table 4.

  More specifically, the photovoltaic element 10C is manufactured as follows. When the production of the photovoltaic element 10C is started, the steps (a), (b), and (c1) described above are sequentially performed using the plasma CVD apparatus 100, and the p layer 3 and the base layer 401A are insulated substrates. The first transparent conductive film 2 is sequentially formed. In this case, the base layer 401A is formed using the upper formation conditions of the i layer in Table 4.

When 10 minutes have elapsed from the start of the formation of the underlayer 401A, the flow rate of SiH ₄ gas is reduced to 3.6 sccm while continuing to apply high-frequency power of 3.0 kW from the high-frequency power source 200 to the antennas 130 and 140, and the underlayer 401A A thin film is grown on it for 150-500 minutes (see bottom of i layer in Table 4). In this case, the dilution rate of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ ) is 11.8%.

  Then, a plurality of crystal regions 402 grow using a plurality of crystal nuclei 413 as seeds, and a thin film 410 in which amorphous regions 401 and crystal regions 402 are alternately arranged in the in-plane direction of the insulating substrate 1 is formed on the p layer 3. (See (d2) of FIG. 13).

Thus, the thin film 410 first forms the underlying layer 401A with a relatively high dilution ratio of SiH ₄ gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )), and then SiH ₄ It is formed by growing the thin film by reducing the dilution ratio of the gas with H ₂ gas (= SiH ₄ / (SiH ₄ + H ₂ )).

Thereafter, the sample is taken out from the plasma CVD apparatus 100, and the taken-out sample is immersed in a mixed solution of hydrofluoric acid and ethanol to change the amorphous region 401 into the amorphous region 403, and then subjected to electrochemical treatment (anodization). ) To form crystal grains 414 at the interface between the amorphous thin film 403 and the crystalline thin film 402 (see (e2) in FIG. 14). In this case, the electrochemical treatment is 1-50 wt. In a solution containing 1% hydrofluoric acid (HF), a current having a current density of 10 to 100 mA / cm ² is passed.

  Subsequently, the sample is immersed in a solution containing a metal complex or an organic dye molecule, and a light absorbing material 415 is formed around the crystal grains 414 by anodic oxidation. Thus, the i layer 40A is formed on the p layer 3 (see (f2) in FIG. 14).

  Thereafter, the sample is set again in the plasma CVD apparatus 100, and the above-described n layer 5 and electrode 6 are sequentially formed on the i layer 40A. Thus, the photovoltaic element 100C is completed (see (g2) in FIG. 14).

  In the photovoltaic device 10 </ b> C, the amorphous region 403 mainly plays a role of absorbing light to generate electron-hole pairs, and the crystal region 402 is generated by the amorphous region 403. It plays the role of suppressing the recombination and moving the pair to the n layer 5 side and the p layer side 3 respectively.

  Since the amorphous region 403 is made of porous silicon as described above, it absorbs light incident from the transparent conductive film 2 side while performing multiple reflection. As a result, the light absorption amount in the amorphous region 403 is larger than the light absorption amount in the amorphous region 401.

  In addition, since the i layer 40A includes the crystal grains 414 and the light absorbing material 415 at the interface between the amorphous region 403 and the crystalline region 402, the i-layer 40A is made of porous silicon (a-Si: H) constituting the amorphous region 403. It also absorbs light having a wavelength in the range of about 730 nm to 800 nm that cannot be absorbed.

  Therefore, the photovoltaic element 10C absorbs more light than the photovoltaic element 10B.

  Further, since the crystal grain 414 and the light absorbing material 415 are formed at the interface between the amorphous region 403 and the crystalline region 402, the electron-hole pair generated by the light absorption by the crystal grain 414 and the light absorbing material 415 is performed. Moves to the crystal region 402 with little recombination and contributes to power generation.

  Therefore, the conversion efficiency of the photovoltaic element 10C can be made higher than the conversion efficiency of the photovoltaic element 10B.

  FIG. 15 is a configuration diagram of still another photovoltaic element according to the second embodiment. The photovoltaic element according to Embodiment 2 may be the photovoltaic element 10D shown in FIG. Referring to FIG. 15, a photovoltaic element 10D is the same as the photovoltaic element 10B except that the i layer 40 of the photovoltaic element 10B shown in FIG. 8 is replaced with an i layer 40B. .

  The i layer 40 </ b> B has a film thickness D <b> 1 of 300 to 1000 nm and includes a plurality of crystal regions 402 </ b> A and amorphous regions 404. Each of the plurality of crystal regions 402 </ b> A has a substantially columnar structure grown in a direction substantially perpendicular to the insulating substrate 1, and has one end in contact with the p layer 3 and the other end in contact with the amorphous region 404. Each of the plurality of crystal regions 402 </ b> A has a width W <b> 2 and a length L <b> 3 in a direction substantially perpendicular to the insulating substrate 1. As a result, the distance between the other end of each crystal region 402A and n layer 5 is set to L4. The distance between two adjacent crystal regions 402A is W1. Each of the plurality of crystal regions 402A is made of i-type poly-Si.

  The amorphous region 404 is made of i-type a-Si: H and includes crystal grains 411 and a light absorbing material 412. The amorphous region 404 is formed between the p layer 3 and the n layer 5 in contact with the p layer 3, the n layer 5, and the plurality of crystal regions 402A.

  The length L3 of the crystal region 402A is determined according to the film thickness D1 of the i layer 40B. More specifically, the length L3 of the crystal region 402A is relatively longer when the film thickness D1 of the i layer 40B is relatively thick, and the film thickness D1 of the i layer 40B is relatively thin. , Relatively short.

  For example, the length L3 of the crystal region 402A is set to a range of 100 nm to 200 nm when the film thickness D1 of the i layer 40B is 300 nm, and is 850 nm to 950 nm when the film thickness D1 of the i layer 40B is 1000 nm. Set to range.

  Further, the length L3 of the crystal region 402A may be determined such that the distance L4 is substantially constant even when the film thickness D1 of the i layer 40B changes.

  16, FIG. 17, and FIG. 18 are first, second, and third process diagrams showing the manufacturing process of the photovoltaic element 10D shown in FIG. 15, respectively. 16, FIG. 17, and FIG. 18, the manufacturing process of the photovoltaic device 10D will be described on the assumption that the film thickness D1 of the i layer 40B is 300 nm and the length L3 of the crystal region 402A is 200 nm.

  Referring to FIG. 16, photovoltaic element 10 </ b> D is manufactured using the formation conditions shown in Table 5.

  More specifically, the photovoltaic element 10D is manufactured as follows. When the production of the photovoltaic element 10D is started, the steps (a), (b), and (c1) described above are sequentially performed using the plasma CVD apparatus 100, and the p layer 3 and the base layer 401A are insulated substrates. The first transparent conductive film 2 is sequentially formed. In this case, the base layer 401A is formed using the uppermost condition of the i layer in Table 5.

Then, after 10 minutes have passed since the formation of the underlayer 401A, the high frequency power supply 200 is applied to the antennas 130 and 140 while maintaining the flow rates of the SiH ₄ gas and H ₂ gas supplied from the gas supply pipes 150 and 160. The high frequency power is reduced to 0.5 to 1.0 kW, and a thin film is grown on the base layer 401A for 10 minutes (see the second stage of the i layer in Table 5). As a result, a thin film 4013 including a part of the amorphous region 404 and the crystal region 402A is formed on the p layer 3 (see (d3) in FIG. 16).

Thereafter, the high-frequency power applied from the high-frequency power source 200 to the antennas 130 and 140 is increased to 2.0 kW while maintaining the flow rates of the SiH ₄ gas and H ₂ gas supplied from the gas supply pipes 150 and 160, and the thin film is formed. Grow for 10 minutes (see third stage of i layer in Table 5). Thus, a thin film 4014 including a part of the amorphous region 404 including the crystal grains 411 and the crystal region 402A is formed over the thin film 4013 (see (e3) in FIG. 16).

  Then, the step (d3) and the step (e3) are repeatedly performed until the length L3 of the crystal region 402A reaches 200 nm, and the amorphous regions 404 and the crystal regions 402A are alternately arranged in the in-plane direction of the substrate 1. A part of the i layer 40B is formed on the p layer 3 (see (f3) in FIG. 17).

Subsequently, 20 to 30 sccm of SiH ₄ gas and 27 sccm of H ₂ gas are supplied from the gas supply pipes 150 and 160, and the high frequency power applied from the high frequency power source 200 to the antennas 130 and 140 is 0.1 to 0.3 kW. The thin film is allowed to grow for 10 minutes (see the fourth stage of the i layer in Table 5). Thereby, a thin film 4015 made of a-Si: H is formed on the amorphous region 404 and the crystalline region 402A (see (g3) in FIG. 17).

Thereafter, 5 to 10 sccm SiH ₄ gas and 27 sccm H ₂ gas are supplied from the gas supply pipes 150 and 160, the high frequency power applied from the high frequency power source 200 to the antennas 130 and 140 is increased to 2.0 kW, and the thin film For 10 minutes (see the bottom of the i layer in Table 5). Thus, a thin film 4016 made of a-Si: H containing crystal grains 411 is formed (see (h3) in FIG. 17).

  Then, the step (g3) and the step (h3) are repeatedly performed until the film thickness of the i layer 40B reaches 300 nm, and the amorphous region 404 and the crystal region 402A including the crystal grains 411 are formed on the p layer 3. (See (j1) in FIG. 18).

  Then, the sample is taken out from the plasma CVD apparatus 100, the taken-out sample is immersed in a solution containing a metal complex or an organic dye molecule, and anodization is performed, and the light absorbing material 412 is bonded around the crystal grains 411. Thereby, the i layer 40B is formed (see (k1) in FIG. 18).

  Thereafter, the n layer 5 and the electrode 6 described above are sequentially formed on the i layer 40B to complete the photovoltaic device 10D (see (m1) in FIG. 18).

  The energy band diagram of the region in which the crystal regions 402A and the amorphous regions 404 are alternately arranged in the in-plane direction of the insulating substrate 1 in the i layer 40B of the photovoltaic element 10D is the energy band diagram shown in FIG. Therefore, the electrons and holes generated in this region travel mainly in the crystal region 402A and contribute to power generation as described above.

  As a result, in the photovoltaic device 10D, the transport characteristics of the photogenerated electrons and holes are improved as compared with the case where the i layer is entirely composed of a-Si: H.

  Therefore, the conversion efficiency of the photovoltaic element 10D can be made higher than that of the photovoltaic element in which all i layers are made of a-Si: H.

  FIG. 19 is a schematic cross-sectional view of still another photovoltaic device according to the second embodiment. The photovoltaic element according to Embodiment 2 may be the photovoltaic element 10E shown in FIG. Referring to FIG. 19, a photovoltaic element 10E is the same as the photovoltaic element 10B except that the i layer 40 of the photovoltaic element 10B shown in FIG. 8 is replaced with an i layer 40C. .

  The i layer 40C has a film thickness D1 of 300 to 1000 nm, and includes a plurality of crystal regions 402B and an amorphous region 405. Each of the plurality of crystal regions 402B has a substantially columnar structure grown in a direction substantially perpendicular to the insulating substrate 1, and has one end in contact with the n layer 5 and the other end in contact with the amorphous region 405. Each of the plurality of crystal regions 402B has a width W2 and a length L5 in a direction substantially perpendicular to the insulating substrate 1. As a result, the distance between the other end of each crystal region 402B and p layer 3 is set to L6. The distance between two adjacent crystal regions 402B is W1. Each of the plurality of crystal regions 402B is made of i-type poly-Si.

  The amorphous region 405 is made of i-type a-Si: H and includes crystal grains 411 and a light absorbing material 412. The amorphous region 405 is formed between the p layer 3 and the n layer 5 in contact with the p layer 3, the n layer 5, and the plurality of crystal regions 402B.

  The length L5 of the crystal region 402B is determined according to the film thickness D1 of the i layer 40C. More specifically, the length L5 of the crystal region 402C is relatively longer when the film thickness D1 of the i layer 40C is relatively thicker, and is longer when the film thickness D1 of the i layer 40C is relatively thinner. , Relatively short.

  For example, the length L5 of the crystal region 402B is set to a range of 100 nm to 200 nm when the film thickness D1 of the i layer 40C is 300 nm, and is 850 nm to 950 nm when the film thickness D1 of the i layer 40C is 1000 nm. Set to range.

  Further, the length L5 of the crystal region 402B may be determined such that the distance L6 is substantially constant even when the film thickness D1 of the i layer 40C changes.

  20, FIG. 21, and FIG. 22 are first, second, and third process diagrams respectively showing manufacturing steps of the photovoltaic element 10E shown in FIG. 20, 21 and 22, the manufacturing process of the photovoltaic device 10E will be described on the assumption that the film thickness D1 of the i layer 40C is 300 nm and the length L5 of the crystal region 402B is 200 nm.

  Referring to FIG. 20, photovoltaic element 10E is manufactured using the formation conditions shown in Table 6.

  More specifically, the photovoltaic element 10E is manufactured as follows. When the production of the photovoltaic element 10E is started, the steps (a) and (b) described above are sequentially performed using the plasma CVD apparatus 100, and the p layer 3 is formed on the transparent conductive film 2 of the insulating substrate 1. Sequentially formed.

Then, 20 to 30 sccm of SiH ₄ gas and 27 sccm of H ₂ gas are supplied from the gas supply pipes 150 and 160, and high frequency power of 0.1 to 0.3 kW is applied from the high frequency power source 200 to the antennas 130 and 140. A thin film is grown on the p-layer 3 for 10 minutes (see the uppermost stage of the i-layer in Table 6). Thereby, a thin film 4017 made of a-Si: H is formed on the p-layer 3 (see (c2) in FIG. 20).

Thereafter, 5-10 sccm SiH ₄ gas and 27 sccm H ₂ gas are supplied to the reaction chamber 110 from the gas supply pipes 150, 160, and 2.0 kW high-frequency power is applied from the high-frequency power source 200 to the antennas 130, 140, The thin film is grown for 10 minutes (see the second stage of the i layer in Table 6). Thus, a thin film 4018 including crystal grains 411 is formed (see (d4) in FIG. 20).

  Then, steps (c2) and (d4) are repeatedly executed until the length L6 of the amorphous region 405 reaches 100 nm, and a thin film 4051 made of a-Si: H is formed on the p layer 3 (FIG. 20 (e4)).

Subsequently, the high-frequency power applied from the high-frequency power source 200 to the antennas 130 and 140 is increased to 3.0 kW while maintaining the flow rates of the SiH ₄ gas and H ₂ gas supplied from the gas supply pipes 150 and 160, and the thin film For 10 minutes (see third stage of i layer in Table 6). Thus, a base layer 401A including crystal nuclei 413 is formed on the thin film 4051 (see (f4) in FIG. 21).

Thereafter, the high frequency power supplied from the high frequency power source 200 to the antennas 130 and 140 is lowered to 0.5 to 1.0 kW while maintaining the flow rates of the SiH ₄ gas and H ₂ gas supplied from the gas supply pipes 150 and 160. Then, the thin film is grown for 10 minutes (see the fourth stage of the i layer in Table 6). Accordingly, a thin film 4019 including a part of the amorphous region 405 and a part of the crystal region 402B is formed (see (g4) in FIG. 21).

Then, while maintaining the flow rates of SiH ₄ gas and H ₂ gas supplied from the gas supply pipes 150 and 160, the high frequency power applied from the high frequency power source 200 to the antennas 130 and 140 is increased to 2.0 kW, and the thin film is formed. Grow for 10 minutes (see bottom of i layer in Table 6). Accordingly, a thin film 4020 including a part of the amorphous region 405 including the crystal grains 411 and a part of the crystal region 402B is formed over the thin film 4019 (see (h4) in FIG. 21).

  Thereafter, the step (g4) and the step (h4) are repeatedly performed until the film thickness of the i layer 40C reaches 300 nm, that is, until the length L5 of the crystal region 402B reaches 200 nm. A thin film 4052 including the region 405 and the crystal region 402B is formed on the p layer 3 (see (j2) in FIG. 22).

  Then, the sample is taken out from the plasma CVD apparatus 100, the taken-out sample is immersed in a solution containing a metal complex or an organic dye molecule, and anodization is performed, and the light absorbing material 412 is bonded around the crystal grains 411. Thereby, the i layer 40C is formed (see (k2) in FIG. 22).

  Thereafter, the n layer 5 and the electrode 6 described above are sequentially formed on the i layer 40C to complete the photovoltaic device 10E (see (m2) in FIG. 22).

  In the i layer 40C of the photovoltaic element 10E, the energy band diagram of the region in which the crystal regions 402B and the amorphous regions 405 are alternately arranged in the in-plane direction of the insulating substrate 1 is shown in FIG. Therefore, the electrons and holes generated in this region travel mainly in the crystal region 402B as described above.

  As a result, in the photovoltaic device 10E, electrons and holes generated at a position far from the light incident surface side (p layer 3 side) (that is, electrons generated by light on the long wavelength side of sunlight). And the transport property of holes) is improved as compared with the case where the i layer is entirely composed of a-Si: H.

  Therefore, the conversion efficiency of the photovoltaic device 10E can be made higher than that of the photovoltaic device in which all i layers are made of a-Si: H.

  In the photovoltaic element 10E, the region made of a-Si: H is disposed on the light incident surface side, and the crystal region 402B is disposed at a position far from the light incident surface. 10E converts short wavelength light into electricity in a region close to the light incident surface, and converts long wavelength light into electricity in a region far from the light incident surface.

  As a result, light from short wavelengths to long wavelengths can be efficiently converted into electricity, and the conversion efficiency can be improved.

  Further, the photovoltaic element according to the second embodiment is different from the crystal grain 411 and the light absorbing material 412 in the amorphous region 404 of the i layer 40B of the photovoltaic element 10D shown in FIG. A photovoltaic element instead of 415 may be used.

  Furthermore, the photovoltaic device according to the second embodiment includes the crystal grain 411 and the light absorbing material 412 of the amorphous region 405 of the i layer 40C of the photovoltaic device 10E shown in FIG. A photovoltaic element instead of 415 may be used.

  Furthermore, the photovoltaic device according to the second embodiment includes the photovoltaic device 10B shown in FIG. 8, the photovoltaic device 10C shown in FIG. 12, the photovoltaic device 10D shown in FIG. 15, and the photovoltaic device shown in FIG. A photovoltaic element obtained by changing any of the elements 10E to the type of the photovoltaic element 10A shown in FIG. 7 may be used.

  In the above description, it has been described that the crystal grains 411 and the light absorbing material 412 are formed in all of the plurality of amorphous regions 401, 404, and 405. 411 and the light absorbing material 412 may be formed in at least one amorphous region 401, 404, 405 of the plurality of amorphous regions 401, 404, 405.

  The number of crystal grains 411 formed in at least one amorphous region 401, 404, 405 of the plurality of amorphous regions 401, 404, 405 may be n (n is a positive integer). The number of light-absorbing substances 412 bonded to one crystal grain 411 may be m (m is a positive integer). The same applies to the crystal grains 414 and the light absorbing material 415.

  In the above description, the crystal grains 411 and the light-absorbing substance 412 have been described as being formed at all of the plurality of interfaces between the plurality of amorphous regions 401 and the plurality of crystal regions 402. Not only this but the crystal grain 411 and the light absorption material 412 should just be formed in the at least 1 interface of several interface.

  The number of crystal grains 411 formed on at least one interface may be n, and the number of light absorbing materials 412 bonded to one crystal grain 411 may be m. The same applies to the crystal grains 414 and the light absorbing material 415.

  Others are the same as in the first embodiment.

In the above description, the transparent conductive films 2 and 12 are made of ITO. However, the present invention is not limited to this, and the transparent conductive films 2 and 12 are made of ZnO (Zinc Oxide) and SnO ₂ (Tin Oxide). ).

  Moreover, the transparent conductive films 2 and 12 and the substrate 11 may be textured.

  Further, in the above description, the i layer 4 is composed of a-Si: H and poly-Si. However, in the present invention, the i layer 4 is not limited thereto, and the i layer 4 is composed of hydrogenated amorphous germanium (a-Ge). : H) and crystalline germanium (c-Ge), hydrogenated amorphous silicon germanium (a-SiGe: H), and crystalline silicon germanium.

  In the present invention, the crystal grains 411 and / or the light absorbing material 412 constitute a “material” that increases the amount of light absorption.

  In the present invention, the crystal grains 414 and / or the light absorbing substance 415 constitute a “substance” that increases the amount of light absorption.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a photovoltaic device that can be easily manufactured at low cost. The present invention is also applied to a photovoltaic device that can improve the conversion efficiency. Furthermore, the present invention is applied to a method for manufacturing a photovoltaic device that can be easily manufactured at low cost. Furthermore, the present invention is applied to a method for manufacturing a photovoltaic device capable of improving the conversion efficiency.

It is a schematic sectional drawing of the photovoltaic element by Embodiment 1 of this invention. It is a schematic sectional drawing of a plasma CVD (Chemical Vapor Deposition) apparatus. It is a top view of the plasma CVD apparatus seen from the A direction shown in FIG. FIG. 2 is a first process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 1. FIG. 3 is a second process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 1. It is an energy band figure of the photovoltaic element shown in FIG. 3 is a schematic cross-sectional view of another photovoltaic element according to Embodiment 1. FIG. 3 is a schematic cross-sectional view of a photovoltaic element according to Embodiment 2. FIG. FIG. 9 is a first process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 8. FIG. 9 is a second process diagram showing manufacturing processes of the photovoltaic element shown in FIG. 8. It is an energy band figure in the surface direction of the insulated substrate 1 of i layer shown in FIG. 6 is a schematic cross-sectional view of another photovoltaic element according to Embodiment 2. FIG. FIG. 13 is a first process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 12. FIG. 13 is a second process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 12. FIG. 6 is a configuration diagram of still another photovoltaic element according to Embodiment 2. FIG. 16 is a first process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 15. FIG. 16 is a second process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 15. FIG. 16 is a third process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 15. 6 is a schematic cross-sectional view of still another photovoltaic element according to Embodiment 2. FIG. FIG. 20 is a first process diagram showing a manufacturing process of the photovoltaic element shown in FIG. 19. FIG. 20 is a second process diagram showing manufacturing processes of the photovoltaic element shown in FIG. 19. FIG. 20 is a third process diagram showing the manufacturing process of the photovoltaic element shown in FIG. 19.

Explanation of symbols

  1, 11 substrate, 2, 12 transparent conductive film, 3 p layer, 4, 4A, 4B, 40, 40A, 40B, 40C i layer, 5 n layer, 6 electrodes, 10, 10A, 10B, 10C, 10D, 10E Photovoltaic element, 41 Amorphous thin film, 42 Crystal thin film, 100 Plasma CVD apparatus, 110 Reaction chamber, 110A, 120A Side wall, 110B, 120B Bottom, 110C Top, 111 Exhaust pipe, 120 Transport chamber, 121 Open / close door, 130 , 140 antenna, 150, 160 gas supply pipe, 170 support base, 180 arm, 190 heater, 200 high frequency power supply, 300 sample, 401, 403, 404, 405 amorphous region, 401A underlayer, 402, 402A, 402B crystal Region, 411, 414 crystal grain, 412, 415 light absorbing material, 413 crystal nucleus, 401 ～4020,4051,4052 thin film.

Claims (10)

A substrate made of a material different from that of a semiconductor that converts light into electricity;
A first semiconductor layer formed on the substrate and having a first conductivity type;
A second semiconductor layer formed on the first semiconductor layer for converting light into electricity;
A third semiconductor layer formed on the second semiconductor layer and having a second conductivity type different from the first conductivity type;
The second semiconductor layer is a photovoltaic element including an amorphous phase, a crystalline phase, and a substance that increases light absorption. The second semiconductor layer includes
A plurality of fourth semiconductor layers comprising the amorphous phase;
A plurality of fifth semiconductor layers comprising the crystalline phase;
N (n is a positive integer) number of sixth semiconductor layers formed in at least one fourth semiconductor layer of the plurality of fourth semiconductor layers, each consisting of nano-sized crystal grains;
And m (m is a positive integer) light absorbing materials coupled to at least one of the n sixth semiconductor layers, each absorbing light having a wavelength in a predetermined range. The photovoltaic element as described in.   The photovoltaic element according to claim 2, wherein each of the plurality of fourth semiconductor layers is made of a porous amorphous phase. The second semiconductor layer includes
A plurality of fourth semiconductor layers comprising the amorphous phase;
A plurality of fifth semiconductor layers comprising the crystalline phase;
N (n is a positive integer) number of sixth semiconductor layers arranged around at least one of the plurality of fifth semiconductor layers, each consisting of nano-sized crystal grains;
And m (m is a positive integer) light absorbing materials coupled to at least one of the n sixth semiconductor layers, each absorbing light having a wavelength in a predetermined range. The photovoltaic element as described in.   5. The photovoltaic element according to claim 2, wherein each of the m light absorbing substances is made of a metal complex or an organic dye molecule.   Each of the plurality of fifth semiconductor layers has one end in contact with one of the first and third semiconductor layers, and the other end connected to either one of the first and third semiconductor layers. 6. The photovoltaic element according to claim 1, comprising a columnar structure formed in contact with and extending in a direction from the first semiconductor layer toward the third semiconductor layer. 6. Forming a first semiconductor layer having a first conductivity type on a substrate made of a material different from that of a semiconductor that converts light into electricity;
A second step of forming, on the first semiconductor layer, a second semiconductor layer containing light that converts light into electricity and includes an amorphous phase, a crystalline phase, and a substance that increases light absorption;
And a third step of forming a third semiconductor layer having a second conductivity type different from the first conductivity type on the second semiconductor layer. The second semiconductor layer includes
A plurality of fourth semiconductor layers comprising the amorphous phase;
A plurality of fifth semiconductor layers comprising the crystalline phase;
N (n is a positive integer) number of sixth semiconductor layers formed in at least one fourth semiconductor layer of the plurality of fourth semiconductor layers, each consisting of nano-sized crystal grains;
M (m is a positive integer) light absorbing materials coupled to at least one of the n sixth semiconductor layers, each absorbing light having a wavelength in a predetermined range,
The second step of the method for manufacturing the photovoltaic element is:
A first sub-step of forming a plurality of crystal nuclei on the first semiconductor layer;
The plurality of fourth semiconductor layers, the plurality of fifth semiconductor layers, and the n number of sixth semiconductor layers are formed so that the plurality of fourth semiconductor layers are formed on the plurality of crystal nuclei. A second substep to:
The method for manufacturing a photovoltaic device according to claim 7, further comprising a third sub-step of forming the m light absorbing materials. The second sub-step includes
Depositing the fourth and fifth semiconductor layers under conditions to form the amorphous phase;
Depositing the sixth semiconductor layer B;
The method for manufacturing a photovoltaic device according to claim 8, comprising: step C in which the step A and the step B are repeatedly executed a predetermined number of times. The second semiconductor layer includes
A plurality of fourth semiconductor layers comprising the amorphous phase;
A plurality of fifth semiconductor layers comprising the crystalline phase;
N (n is a positive integer) number of sixth semiconductor layers formed in at least one fourth semiconductor layer of the plurality of fourth semiconductor layers, each consisting of nano-sized crystal grains;
M (m is a positive integer) light absorbing materials coupled to at least one of the n sixth semiconductor layers, each absorbing light having a wavelength in a predetermined range,
The second step of the method for manufacturing the photovoltaic element is:
A first sub-step of forming a plurality of crystal nuclei on the first semiconductor layer;
A second sub-step of forming the plurality of fourth semiconductor layers and the plurality of fifth semiconductor layers such that the plurality of fourth semiconductor layers are formed on the plurality of crystal nuclei;
A third sub-step of making the plurality of fourth semiconductor layers porous;
The method for manufacturing a photovoltaic device according to claim 7, further comprising: a fourth sub-step of forming the m light absorbing materials in the porous fourth semiconductor layer.

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