JP5562568B2 - Schottky type solar cell and manufacturing method - Google Patents

Description

  The present invention relates to an improvement in efficiency of a Schottky type solar cell, and includes a nanomesh metal electrode having a submicron opening in a Schottky type metal electrode. It also relates to the manufacturing method.

  Since the Schottky solar cell uses light absorption in the vicinity of the semiconductor electrode interface with the metal electrode on the light irradiation surface, a large output current can be obtained. Further, since light absorption near the interface between the metal electrode and the semiconductor is used, it can be applied to an amorphous or polycrystalline thin film solar cell. However, since the light irradiation surface is covered with metal, the metal film must be very thin (-10 nm) in order to reduce absorption and reflection. Further, a material having a small absorption coefficient due to light absorption near the interface cannot provide sufficient conversion efficiency of the solar cell.

  As a method for improving the efficiency of a Schottky type solar cell, there is a method in which a transparent electrode is used for a light irradiation surface and a back electrode is a Schottky metal electrode and has an uneven structure (see Patent Document 1). In this method, the absorption of light taken from the transparent electrode is assisted by the plasmon enhancement effect to improve the conversion efficiency. However, in this method, since the amount of light to be captured is received from the transparent electrode, the efficiency is slightly improved or almost the same as the conventional method.

JP 2008-53165 A

  Since a conventional Schottky solar cell uses a metal electrode on the light irradiation surface, the metal film must be very thin (-10 nm). Moreover, sufficient solar cell conversion efficiency cannot be obtained with a material that does not have a large absorption coefficient due to light absorption in the vicinity of the metal electrode-semiconductor interface. In the present invention, the conversion efficiency is improved by having a fine opening in the electrode of the Schottky solar cell.

A solar cell according to an embodiment of the present invention is a solar cell configured by laminating a first electrode layer, a semiconductor layer, and a second electrode, and the first electrode layer is on a light irradiation surface side. An electrode having a semiconductor layer and a Schottky wall, wherein the second electrode layer is on an opposite side of the light irradiation surface, and has an ohmic contact with the semiconductor layer, Having a plurality of openings penetrating the electrode layer, the area per opening is in the range of 80 nm ^{2 to} 0.25 μm ² , the opening ratio is in the range of 10% to 66%, The film thickness is in the range of 5 nm to 50 nm.

  A method for manufacturing a solar cell according to another embodiment of the present invention is a method for manufacturing the solar cell, the step of forming a semiconductor layer, the step of forming a second electrode layer of the semiconductor layer, Including a step of forming a first electrode layer of a semiconductor layer, a step of preparing a stamper having a fine concavo-convex pattern corresponding to an opening on a surface thereof, and a resist using the stamper as at least a part of the first electrode The method includes a step of transferring a pattern and a step of forming a pattern on the first electrode layer using the resist pattern as an etching mask.

  ADVANTAGE OF THE INVENTION According to this invention, a solar cell with sufficient conversion efficiency is provided by using the nano mesh metal electrode which has a submicron opening for the metal electrode of the light-receiving surface of a Schottky type solar cell.

The graph which shows the relationship between the opening diameter of an opening part, and an electric field strength. The conceptual diagram for demonstrating the difference of the Schottky type solar cell of a prior art example, and the Schottky type solar cell which concerns on this Embodiment. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 1. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 2. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 3. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 4. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 5. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 6. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 7. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 8. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 9. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 10. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 11. FIG. The conceptual diagram for demonstrating the manufacturing method of the solar cell which concerns on Example 12. FIG.

  The present invention is characterized in that the metal electrode on the light-receiving surface of a Schottky solar cell is a nanomesh metal electrode having a submicron opening. By using a nanomesh metal, a strong localized electric field generated in the opening portion excites more carriers than usual near the nanomesh metal electrode and the semiconductor interface, thereby improving the conversion efficiency of the solar cell. In addition, since more carriers than usual are excited in the vicinity of the interface between the nanomesh metal and the semiconductor, even a material having a small absorption coefficient can be used. Furthermore, it is not necessary to make the metal film thickness less than 10 nm, which contributes to the improvement of reliability.

  A significant difference from that shown in Patent Document 1 is that the energy of the light to be captured increases. In Patent Document 1, light that cannot be absorbed by the light absorption layer is assisted by the plasmon enhancement effect to improve the efficiency. In our invention, the amount of energy of light taken in is increased. In our invention, the efficiency of the solar cell is greatly improved. In addition, in connection with a metal electrode having an opening, a solar cell having a metal electrode having an aperture arrangement having a strengthening characteristic due to a resonance interaction between incident light and surface plasmon on the surface has been devised (Japanese Patent Laid-Open No. 2002-2000). -76410). Since the plasmon resonance action is used, the conversion efficiency is improved by utilizing the phenomenon that the transmittance of a specific wavelength in the metal electrode is improved. In this method, it is considered that the transmittance of a specific wavelength only increases and does not contribute so much to the efficiency improvement of the solar cell. This is very different from our invention because it is not the principle of increasing the transmittance of the metal electrode.

  The details of the present invention will be described below with reference to the illustrated embodiments. First, the principle of the present invention will be described in detail.

  In order to investigate the state of a strong local electric field generated in the opening by using a nano-mesh metal electrode having a submicron opening, a simulation was performed by the Finite Difference Time Domain (FDTD) method. In the simulation, a structure of Si / Al (50 nm) / air was used, and a single opening was prepared in Al. The Al opening diameter was changed in the range of 10 nm to 500 nm, light (wavelength 500 nm) was incident from the air side, and the dependence of the electric field strength generated at the interface between Si and Al was investigated. The result is shown in FIG. First, simulation results show that the electric field enhancement occurs at the edge of the Al opening. The electric field strength was almost constant when the opening diameter was 200 nm or more, but the electric field strength gradually increased when the opening diameter was 100 nm or less. The electric field strength became maximum at around 40 to 60 nm, and the electric field strength decreased at an opening diameter smaller than that. Further, the dependency of the electric field strength was examined by changing the wavelength of incident light with the above structure to 1000 nm and changing the aperture diameter of Al in the range of 10 nm to 1000 nm. The result is shown in FIG. The electric field strength was almost constant when the aperture diameter was 400 nm or more, but the electric field strength gradually increased when the aperture diameter was 200 nm or less, and the electric field strength reached a maximum near 80 to 120 nm. It was. It was found that when the incident wavelength was changed from 500 nm to 1000 nm, the peak value of the electric field enhancement aperture diameter was doubled as the wavelength was doubled. Judging from the above simulation results, it was found that the electric field is sufficiently enhanced at the interface between Si and Al when an aperture of 10 nm to 200 nm exists in AM1.5 light.

  The above simulation results only show the result for a single opening of Al and do not take into account the effect of the number when there are multiple openings. The dependence of the electric field enhancement when the aperture actually exists in the form of close packing was investigated. Since the electric field enhancement exists at the edge, assuming that the aperture shape is a circle, the result of FIG. 1A is multiplied by 4 * π / √3 / aperture diameter. The result is shown in FIG. The result was the same as in FIG. 1A, but shifted to the short wavelength side due to the 1 / aperture diameter. However, in AM1.5 light, the presence of an aperture of 10 nm or more and 200 nm or less did not change the electric field sufficiently. From the above results, it was found that by using a nanomesh metal electrode, a strong local electric field generated at the opening is generated, thereby improving the conversion efficiency of the Schottky solar cell. However, here, the calculation is made with Al as the metal and the opening as a circle, but in reality, the same thing occurs with a metal other than Al, and there is no problem with a shape other than a circle.

  Next, how the strong local electric field generated at the opening of the nanomesh electrode contributes to the improvement of the solar cell efficiency will be described. From the above simulation results. When the electrode structure is made of nanomesh metal, a strong local electric field is generated in the opening. As shown in FIG. 2A, in a normal Schottky solar cell, incident light excites carriers near the interface between the metal electrode and the semiconductor to generate a photocurrent and generate electric power. When a Schottky solar cell has a nanomesh electrode, a strong local electric field generated at the opening of the nanomesh electrode as shown in FIG. More carriers are excited and more photocurrent is generated, that is, more power is generated. Thereby, the conversion efficiency of the solar cell can be improved.

Next, the photocurrent generated in the Schottky solar cell will be described, and an effective structure will be described. In the Schottky solar cell, three types of photocurrents are generated. First, light with energy exceeding the Schottky barrier is absorbed by the metal, excites electrons, and is injected into the semiconductor. Second, light with energy exceeding the band gap of the semiconductor is absorbed near the surface, that is, in the depletion layer. Third, long wavelength light is absorbed in the neutral region of the semiconductor. Among the three, light absorption in the second depletion layer region is large, and the depletion layer width W is expressed by the following equation.
W = (2 * εs * Vbi / q / ND) ^0.5 (1)
Here, εs is the dielectric constant of the semiconductor, Vbi is the internal potential, and ND is the doping concentration of the semiconductor (in this case, n-type is assumed). When the semiconductor is Si, Vbi is about 0.5 eV, ND is used at about 10 ¹⁶ cm ^{−3 in the} solar cell, and the depletion layer width W is calculated to be about 0.3 μm from the equation (1). When the metal electrode does not have a nanomesh structure, a depletion layer of about 0.3 μm is formed in the entire region from the metal-semiconductor interface. When the metal electrode has a nanomesh structure, the depletion layer is formed with a depletion layer of about 0.3 μm in the region immediately below the nanomesh metal electrode-semiconductor interface and directly below the electrode, and the 0 from the nanomesh metal electrode edge to the opening A depletion layer of about 3 μm is formed. Therefore, when the opening diameter of the nanomesh electrode is larger than 0.6 μm, a depletion layer is not formed near the center of the opening, and light absorption is not sufficient. Therefore, the opening diameter of the nanomesh electrode is preferably smaller than 0.6 μm, and 0.5 μm or less is preferable for more sufficient light absorption. In addition, as described above in a Schottky solar cell, light with energy exceeding the Schottky barrier is absorbed by the metal, excites electrons, and is injected into the semiconductor and light absorbed in the neutral region of the semiconductor. Since electric current is also generated, the nanomesh electrode should not be too thick, and a film thickness of 50 nm or less is preferable.

  In addition, there is a Metal Insulator Semiconductor (MIS) solar cell in which an insulating film is sandwiched between a metal and a semiconductor in a Schottky type solar cell, which will be briefly described. The basic operating principle of the solar cell with the MIS structure is the same as that of the Schottky type solar cell, but a tunnel current is generated through the insulating film because the insulating film exists. Therefore, the open circuit voltage becomes larger than that of the Schottky solar cell, and the open circuit voltage increases as the thickness of the insulating film increases. However, as the film thickness increases, the short-circuit current decreases due to the tunnel current decreasing. Therefore, when the conversion efficiency of the solar cell is taken into consideration, the optimum film thickness is around several nm. Also in the solar cell having the MIS structure, conversion efficiency can be improved by using a metal electrode as a nanomesh electrode.

Next, a method for manufacturing the solar cell will be described.
In order to form a metal electrode pattern having an opening of 200 nm or less, it is necessary to use the latest exposure apparatus and EB drawing apparatus used in semiconductor integrated circuits. However, using the latest exposure apparatus and EB drawing apparatus, it seems impossible to form a large area at a low cost. One method that can be formed at a low cost with a large area is a method using nanoimprint. Hereinafter, a method for forming a nanomesh electrode by nanoimprinting will be described.

As the substrate, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ is prepared. The back surface of the n-type Si substrate is doped with P by thermal diffusion so that the back surface concentration is 10 ²⁰ cm ⁻³ . Next, Al is formed on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact is formed on the back surface. Then, 20 nm of Al is formed on the substrate surface by a vapor deposition method. In this case, the substrate surface has a Schottky junction with Al.

  Next, a resist is formed on Al formed on the substrate surface. Then, prepare a quartz mold having a convex shape with a size of 200 nm (the shape is formed within 9 cm 2), and heat up the resist-coated substrate with the convex shape of the quartz mold. Imprint by pressing against the resist. After imprinting, the substrate is cooled and the quartz mold is released. After nanoimprinting, a concave shape having a size of 200 nm is formed on the resist.

  Next, the resist in which the concave pattern is formed is etched by oxygen reactive ion etching (RIE) to perform bottoming. After the bottom, Al is etched by RIE using a chlorine-based gas. After the Al etching, the remaining resist was removed by oxygen ashing to form a shape having an opening in Al. Through the above process, a Schottky solar cell having a nanomesh electrode is completed.

  In addition, a Schottky solar cell having a nanomesh electrode can be formed by a process similar to the above for a compound semiconductor. Examples of the compound semiconductor include GaAs and CdTe.

The invention is explained in more detail by means of examples. The solar cell was produced with a size of 9 cm ² , and the conversion efficiency of the nanomesh metal electrode and the thin film metal solar cell was compared.

Example 1
An n-type Si substrate 1 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 1 was doped with P by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 2 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer 3 having a thickness of 20 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had a Schottky junction with the Al layer 3 (FIG. 3A).

Next, a solution obtained by diluting a resist 4 (THMR IP3250, Tokyo Ohka Kogyo Co., Ltd.) 1: 2 with ethyl lactate (EL) on the Al layer 3 formed on the substrate surface is spin-coated at 2000 rpm for 30 seconds. After that, the solvent was evaporated by heating on a hot plate at 110 ° C. for 90 seconds (FIG. 3B). The film thickness of the resist 4 was 150 nm. Next, a quartz mold 5 (the shape is formed within 9 cm ² ) having a convex shape having a size of 200 nm and a height of 150 nm is prepared, and the substrate 1 with a resist 4 is brought to 120 ° C. Imprinting was performed by pressing the quartz mold 5 having a convex shape against the resist 4 under a pressure of 10 MPa in a heated state (FIG. 3C). After imprinting, the substrate 1 was cooled to room temperature, and the quartz mold 5 was released (FIG. 3D). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 4.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 4 was removed and the Al layer 3 was exposed (FIG. 3E). Next, RIE was performed for 60 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W. A pattern having an opening of 200 nm was formed in the Al layer 3 by RIE of chlorine gas. The remaining resist 4 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 3 (f)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a normal Schottky type solar cell.

  When the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode was compared, an efficiency improvement of 50% was confirmed.

(Example 2)
An n-type Si substrate 11 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 11 was doped with P by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 12 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer 13 having a thickness of 20 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had a Schottky junction with the Al layer 13 (FIG. 4A).

  Next, a solution obtained by diluting a resist 14 (THMR IP3250, Tokyo Ohka Kogyo Co., Ltd.) 1: 1 with ethyl lactate (EL) on the Al layer 13 formed on the surface of the substrate 11 is spin-coated at 2000 rpm for 30 seconds. After that, the solvent was evaporated by heating at 110 ° C. for 90 seconds on a hot plate. Next, the resist 14 was annealed at 250 ° C. in a nitrogen atmosphere and thermally cured. The film thickness of the resist 14 was 300 nm.

  Next, silica particles having a diameter of 200 nm were dispersed in ethyl lactate. The concentration of silica particles was adjusted to 8% by weight. An acrylic monomer was added to the dispersion in a volume ratio of silica: acrylic monomer = 1: 3 to prepare a dispersion. Ethoxylated (6) trimethylpropylene triacrylate (hereinafter referred to as E6TPTA) was used as the acrylic monomer. The dispersion was dropped onto the silicon substrate 11 with the resist 14 and spin-coated under the conditions of 2000 rpm and 60 seconds. After spin coating, baking was performed at 110 ° C. for 60 seconds in order to completely remove the solvent. Thereafter, hardening annealing was performed at 150 ° C. for 1 hour in a nitrogen atmosphere. After annealing, a regularly arranged silica particle layer 15 was formed (FIG. 4B).

Next, the arranged silica particle layers 15 were etched by a reactive etching (RIE) apparatus at a CF ₄ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W for 2 minutes to reduce the particle size of the silica particles to 150 nm. (FIG. 4 (c)).

Next, using the silica particle layer 15 as a mask, the resist 14 was etched for 5 minutes at an O ₂ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W to form a resist pillar pattern 16 (FIG. 4D).

  Next, the organic SOG composition 17 (OCD-T7 T-14000 (trade name), Tokyo Ohka Kogyo Co., Ltd.) was dropped onto the silicon substrate with the resist pillar pattern 16 and spin-coated under the conditions of 2000 rpm and 60 seconds. After spin coating, baking was performed at 110 ° C. for 60 seconds in order to completely remove the solvent. Thereafter, hardening annealing was performed at 250 ° C. for 1 hour in a nitrogen atmosphere. After curing, the resist pillar pattern 16 was completely filled with SOG 17 and flattened (FIG. 4E).

Next, the silicon substrate planarized by SOG 17 was etched back at a CF ₄ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W for 10 minutes. After the etch back, the top of the resist pillar pattern 16 was exposed (FIG. 4F).

Next, the resist pillar 16 was completely removed by etching at an O ₂ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W for 3 minutes. After the removal, a hole pattern of SOG 17 was formed (FIG. 4G).

Next, RIE was performed for 60 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W using the SOG hole pattern as a mask. A pattern having an opening of 150 nm was formed in the Al layer 13 by RIE of chlorine-based gas. The remaining SOG mask was removed by CF ₄ etching to complete a Schottky solar cell with a nanomesh electrode (FIG. 4 (h)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a normal Schottky type solar cell.

  When the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode was compared, an efficiency improvement of 50% was confirmed.

(Example 3)
An n-type Si substrate 21 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 21 was doped with P by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 22 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer 23 having a thickness of 20 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had a Schottky junction with the Al layer 23 (FIG. 5A).

  Next, a solution obtained by diluting the resist 24 1: 1 with EL on the Al layer 23 formed on the substrate surface in the same manner as in Example 2 was spin-coated at 2000 rpm for 30 seconds, and then 110 ° C. on the hot plate. The solvent was evaporated by heating at 0 ° C. for 90 seconds. Next, the resist 24 was annealed at 250 ° C. in a nitrogen atmosphere and thermally cured. The film thickness of the resist 24 was 300 nm. Next, a solution obtained by diluting an organic SOG composition 25 (OCD-T7 5500-T (trade name), manufactured by Tokyo Ohka Kogyo Co., Ltd.) 1: 9 with EL was spin-coated at 2000 rpm for 30 seconds, and then hot The solvent was evaporated by heating at 110 ° C. for 90 seconds on the plate. Next, the resist 24 was annealed at 250 ° C. in a nitrogen atmosphere and thermally cured. The film thickness after curing was 30 nm (FIG. 5B).

  Next, a solution obtained by dissolving a polymer obtained by mixing PMMA (Mw: 1500) at a weight ratio of 6: 4 in propylene glycol monomethyl ether acetate (PGMEA) at 3 wt% with a block polymer of PS (Mw 78000): PMMA (Mw: 170000). Was applied by spin coating at 2000 rpm for 30 seconds and then pre-baked at 110 ° C. for 90 seconds to evaporate the solvent and obtain a film thickness of 120 nm.

Next, annealing was performed at 210 ° C. for 4 hours in a nitrogen atmosphere to separate phases of PS and PMMA, and a polystyrene dot pattern having a diameter of about 90 nm was formed. Thereafter, RIE is performed for 20 seconds under the conditions of O ₂ = 30 sccm, pressure 13.3 Pa (100 mTorr), and power = 100 W, thereby selectively etching PMMA 26 out of phase-separated PS-PMMA to form PS dot pattern 27. (FIG. 5C).

Next, using the PS dot pattern 27 as a mask, etching was performed at a CF ₄ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W for 90 seconds to form an SOG dot pattern 28.

Next, using the SOG dot pattern 28 as a mask, the resist 24 was etched for 5 minutes at an O ₂ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W to form a resist pillar pattern 29 (FIG. 5D).

  Next, in the same manner as in Example 2, the organic SOG composition 30 (OCD-T7 T-14000 (trade name), Tokyo Ohka Kogyo Co., Ltd.) was dropped onto the silicon substrate with the resist pillar pattern 29, and was applied at 2000 rpm for 60 seconds. Spin coat under conditions. After spin coating, baking was performed at 110 ° C. for 60 seconds in order to completely remove the solvent. Thereafter, hardening annealing was performed at 250 ° C. for 1 hour in a nitrogen atmosphere. After curing, the resist pillar pattern 29 was completely filled with SOG 30 and flattened (FIG. 5E).

Next, the silicon substrate planarized by SOG 30 was etched back for 10 minutes at a CF ₄ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W. After the etch back, the top of the resist pillar pattern 29 was exposed (FIG. 5F).

Next, the resist pillar 29 was completely removed by etching at an O ₂ flow rate of 30 sccm, a pressure of 1.33 Pa (10 mTorr), and a power of 100 W for 3 minutes. After the removal, a hole pattern of SOG30 was formed (FIG. 5 (g)).

Next, RIE was performed for 60 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W using the hole pattern of SOG30 as a mask. A pattern having an opening of 100 nm was formed in the Al layer 23 by RIE of chlorine gas. The remaining mask of SOG30 was removed by etching with CF ₄ to complete a Schottky solar cell with a nanomesh electrode (FIG. 5 (h)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a normal Schottky type solar cell.

  When comparing the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode, an efficiency improvement of 60% was confirmed.

(Example 4)
An n-type Si substrate 31 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 31 was doped with P by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 32 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer 33 having a thickness of 10 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had an Al layer 33 and a Schottky junction (FIG. 6A).

Next, a solution obtained by diluting the resist 34 1: 3 with EL on the Al layer 33 formed on the substrate surface is spin-coated at 2000 rpm for 30 seconds, and then heated on a hot plate at 110 ° C. for 90 seconds. The solvent was evaporated (FIG. 6 (b)). The film thickness of the resist 34 was 100 nm. Next, a quartz mold 35 (the shape is formed in 9 cm ² ) having a convex shape having a size of 50 nm and a height of 100 nm is prepared, and the substrate with the resist 34 is heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 35 was pressed against the resist 34 with a pressure of 10 MPa to perform imprinting (FIG. 6C). After imprinting, the substrate was cooled to room temperature and the quartz mold 35 was released (FIG. 6 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 34.

Next, the resist pattern on which the concave pattern was formed was etched for 20 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 34 was removed to expose the Al layer 33 (FIG. 6E). Next, RIE was performed for 45 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W. A pattern having an opening of 50 nm was formed in the Al layer 33 by RIE of chlorine gas. The remaining resist 34 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 6 (f)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a normal Schottky type solar cell.

  When comparing the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode, an improvement in efficiency of 100% was confirmed.

  Compared with Example 1, the opening diameter was made finer, so that the electric field enhancement effect was increased and the efficiency was increased.

(Example 5)
An n-type Si substrate 41 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 41 was doped with P by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 42 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Au layer 43 was formed to 30 nm on the substrate surface by a vapor deposition method. In this case, the substrate surface had a Schottky junction with the Au layer 43 (FIG. 7A).

  Next, a solution obtained by diluting the resist 44 1: 2 with EL on the Au layer 43 formed on the substrate surface in the same manner as in Example 1 was spin-coated at 2000 rpm for 30 seconds, and then 110 ° C. on the hot plate. The solvent was evaporated by heating at 90 ° C. for 90 seconds (FIG. 7B). The film thickness of the resist 44 was 150 nm. Next, a quartz mold 45 (with a shape of 9 cm 2) in which a convex shape having a size of 200 nm and a height of 150 nm was formed was prepared, and the substrate with the resist 44 was heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 45 was pressed against the resist at a pressure of 10 MPa to perform imprinting (FIG. 7C). After imprinting, the substrate was cooled to room temperature and the quartz mold 45 was released (FIG. 7 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 44.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the resist 44 was exposed and the Au layer 43 was exposed (FIG. 7E).

  Next, ion milling was performed for 60 seconds under the conditions of Ar: 30 sccm, power of 500 W, and current of 40 mA. A pattern having an opening of 200 nm was formed in the Au layer 43 by ion milling. The remaining resist 44 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 7 (f)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Au layer was formed to 10 nm on the substrate surface by a vapor deposition method, thereby completing a normal Schottky solar cell.

  When comparing the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode, an efficiency improvement of 60% was confirmed.

(Example 6)
An n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 51 was doped with P by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 52 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Ag layer 53 was formed to 30 nm on the substrate surface by a vapor deposition method. In this case, the substrate surface had an Ag layer 53 and a Schottky junction (FIG. 8A).

Next, a solution obtained by diluting the resist 54 1: 2 with EL on the Ag layer 53 formed on the substrate surface in the same manner as in Example 1 was spin-coated at 2000 rpm for 30 seconds, and then 110 ° C. on the hot plate. The solvent was evaporated by heating at 90 ° C. for 90 seconds (FIG. 8B). The film thickness of the resist 54 was 150 nm. Next, a quartz mold 55 (with a shape of 9 cm ² ) in which a convex shape having a size of 200 nm and a height of 150 nm is formed is prepared, and the substrate with the resist 54 is heated to 120 ° C. In this state, the one with the convex shape of the quartz mold 55 was pressed against the resist 54 with a pressure of 10 MPa to perform imprinting (FIG. 8C). After imprinting, the substrate was cooled to room temperature, and the quartz mold 55 was released (FIG. 8D). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 54.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the resist 54 was exposed and the Ag layer 53 was exposed (FIG. 8E).

  Next, ion milling was performed for 90 seconds under the conditions of Ar: 30 sccm, power of 500 W, and current of 40 mA. A pattern having an opening of 200 nm was formed in the Ag layer 53 by ion milling. The remaining resist 54 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 8 (f)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Ag layer was formed to 20 nm on the substrate surface by a vapor deposition method, thereby completing a normal Schottky solar cell.

  When comparing the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode, an efficiency improvement of 55% was confirmed.

  From the above results, the efficiency improvement effect was confirmed even when Al, Au, Ag and metals were changed. In addition, the effect is similarly exhibited with other metals.

(Example 7)
An n-type GaAs substrate 61 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. An Au—Ge (1%) layer 62 was formed to 100 nm on the back surface of the n-type GaAs substrate 61 by vapor deposition. After the formation, annealing was performed at 450 ° C. for 30 minutes in a nitrogen atmosphere. After annealing, an electrode having ohmic contact was formed on the back surface.

  Next, an Au layer 63 was formed to 30 nm on the substrate surface by vapor deposition. In this case, the substrate surface had an Au layer 63 and a Schottky junction (FIG. 9A).

Next, a solution obtained by diluting the resist 64 1: 2 with EL on the Au layer 63 formed on the substrate surface in the same manner as in Example 1 was spin-coated at 2000 rpm for 30 seconds, and then 110 H on the hot plate. The solvent was evaporated by heating at 90 ° C. for 90 seconds (FIG. 9B). The film thickness of the resist 64 was 150 nm. Next, a quartz mold 65 (with a shape of 9 cm ² ) in which a convex shape having a size of 200 nm and a height of 150 nm is formed is prepared, and the substrate with the resist 64 is heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 65 was pressed against the resist 64 with a pressure of 10 MPa to perform imprinting (FIG. 9C). After imprinting, the substrate was cooled to room temperature, and the quartz mold 65 was released (FIG. 9D). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 64.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 64 was removed to expose the Au layer 63 (FIG. 9E).

  Next, ion milling was performed for 60 seconds under the conditions of Ar: 30 sccm, power of 500 W, and current of 40 mA. A pattern having an opening of 200 nm was formed in the Au layer 63 by ion milling. The remaining resist 64 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 9 (f)).

For comparison, an n-type GaAs substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and Au—Ge (1%) was formed to 100 nm on the back surface of the n-type GaAs substrate by an evaporation method. After the formation, annealing was performed at 450 ° C. for 30 minutes in a nitrogen atmosphere. After annealing, an electrode having ohmic contact was formed on the back surface. Subsequently, 10 nm of Au was formed on the substrate surface by a vapor deposition method to complete a normal Schottky type solar cell.

  When the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode was compared, an efficiency improvement of 50% was confirmed.

(Example 8)
An n-type polysilicon layer having a thickness of 1 μm was formed on the glass substrate 71 with the electrode 72 by a plasma CVD method using a mixed gas of SiH ₄ and PH ₃ . Next, an Al layer 73 having a thickness of 20 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had an Al layer 73 and a Schottky junction (FIG. 10A).

Next, a solution obtained by diluting a resist 74 (THMR IP3250, Tokyo Ohka Kogyo Co., Ltd.) 1: 2 with ethyl lactate (EL) on the Al layer 73 formed on the substrate surface is spin-coated at 2000 rpm for 30 seconds. After that, the solvent was evaporated by heating on a hot plate at 110 ° C. for 90 seconds (FIG. 10B). The film thickness of the resist 74 was 150 nm. Next, a quartz mold 75 (with a shape of 9 cm ² ) in which a convex shape having a size of 200 nm and a height of 150 nm is formed is prepared, and the substrate with the resist 74 is heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 75 was pressed against the resist 74 with a pressure of 10 MPa to perform imprinting (FIG. 10C). After imprinting, the substrate was cooled to room temperature and the quartz mold 75 was released (FIG. 10 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 74.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 74 was removed to expose the Al layer 73 (FIG. 12E). Next, RIE was performed for 60 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W. A pattern having an opening of 200 nm was formed in the Al layer 73 by RIE of chlorine gas. The remaining resist 74 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 10 (f)).

For comparison, an n-type amorphous silicon layer having a thickness of 1 μm was formed on a glass substrate with electrodes by a plasma CVD method using a mixed gas of SiH ₄ and PH ₃ . Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a normal Schottky type solar cell.

For comparison, an n-type polysilicon layer of 1 μm was formed on a glass substrate with electrodes by a plasma CVD method using a mixed gas of SiH ₄ and PH ₃ . Next, Al was formed to 10 nm on the substrate surface by a vapor deposition method, thereby completing a normal Schottky solar cell.

  When the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode was compared, an efficiency improvement of 50% was confirmed.

Example 9
An n-type amorphous silicon layer having a thickness of 1 μm was formed on a glass substrate 81 with an electrode 82 by a plasma CVD method using a mixed gas of SiH ₄ and PH ₃ . Next, an Al layer 83 having a thickness of 20 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had an Al layer 83 and a Schottky junction (FIG. 11A).

Next, a solution obtained by diluting a resist 84 (THMR IP3250, Tokyo Ohka Kogyo Co., Ltd.) 1: 2 with ethyl lactate (EL) on the Al layer 83 formed on the substrate surface is spin-coated at 2000 rpm for 30 seconds. After that, the solvent was evaporated by heating on a hot plate at 110 ° C. for 90 seconds (FIG. 11B). The film thickness of the resist 84 was 150 nm. Next, a quartz mold 85 (with a shape of 9 cm ² ) in which a convex shape having a size of 200 nm and a height of 150 nm is formed is prepared, and the substrate with the resist 84 is heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 85 was pressed against the resist 84 with a pressure of 10 MPa to perform imprinting (FIG. 11C). After imprinting, the substrate was cooled to room temperature and the quartz mold 85 was released (FIG. 11 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 84.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 84 was removed to expose the Al layer 83 (FIG. 10E). Next, RIE was performed for 60 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W. A pattern having an opening of 200 nm was formed in the Al layer 83 by RIE of chlorine gas. The remaining resist 84 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 11 (f)).

For comparison, an n-type amorphous silicon layer having a thickness of 1 μm was formed on a glass substrate with electrodes by a plasma CVD method using a mixed gas of SiH ₄ and PH ₃ . Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a normal Schottky type solar cell.

  When comparing the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode, an efficiency improvement of 55% was confirmed.

(Example 10)
A p-type GaAs substrate 91 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. An Au / Au—Zn (5%) layer 92 was formed to 100 nm on the back surface of the p-type GaAs substrate 91 by vapor deposition. After the formation, annealing was performed at 450 ° C. for 30 minutes in a nitrogen atmosphere. After annealing, an electrode having ohmic contact was formed on the back surface.

  Next, an Au layer 93 was formed to 30 nm on the surface of the substrate by vapor deposition. In this case, the substrate surface had an Au layer 93 and a Schottky junction (FIG. 12A).

  Next, a solution obtained by diluting the resist 94 1: 2 with EL on the Au layer 93 formed on the surface of the substrate in the same manner as in Example 1 was spin-coated at 2000 rpm for 30 seconds, and then 110 H on the hot plate. The solvent was evaporated by heating at 0 ° C. for 90 seconds (FIG. 12B). The film thickness of the resist 94 was 150 nm. Next, a quartz mold 95 (with a shape of 9 cm 2) in which a convex shape having a size of 200 nm and a height of 150 nm was formed was prepared, and the substrate with the resist 94 was heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 95 was pressed against the resist 94 with a pressure of 10 MPa to perform imprinting (FIG. 12C). After imprinting, the substrate was cooled to room temperature and the quartz mold 95 was released (FIG. 12 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 94.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 94 was removed to expose the Au layer 93 (FIG. 11E).

  Next, ion milling was performed for 60 seconds under the conditions of Ar: 30 sccm, power of 500 W, and current of 40 mA. A pattern having an opening of 200 nm was formed in the Au layer 93 by ion milling. The remaining resist 94 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 12 (f)).

For comparison, an n-type GaAs substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and an Au / Au—Zn (5%) layer was formed to 100 nm on the back surface of the p-type GaAs substrate by a vapor deposition method. After the formation, annealing was performed at 450 ° C. for 30 minutes in a nitrogen atmosphere. After annealing, an electrode having ohmic contact was formed on the back surface.

  Next, an Au layer was formed to 10 nm on the substrate surface by a vapor deposition method, thereby completing a normal Schottky solar cell.

  When comparing the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode, an efficiency improvement of 60% was confirmed.

(Example 11)
A p-type Si substrate 101 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the p-type Si substrate 101 was doped with B by thermal diffusion to 10 ²⁰ cm ⁻³ . Next, an Al layer 102 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, a Ni layer was deposited on the surface of the substrate by sputtering, and annealed at 900 ° C. to form a NiSi ₂ layer 103 having a thickness of 30 nm. In this case, the substrate surface had a NiSi ₂ layer 103 and a Schottky junction (FIG. 13A).

Next, a solution obtained by diluting the resist 104 1: 2 with EL on the NiSi ₂ layer 103 formed on the substrate surface in the same manner as in Example 1 was spin-coated at 2000 rpm for 30 seconds, and then on the hot plate. The solvent was evaporated by heating at 110 ° C. for 90 seconds (FIG. 13B). The film thickness of the resist 104 was 150 nm. Next, a quartz mold 105 (with a shape of 9 cm ² ) in which a convex shape having a size of 200 nm and a height of 150 nm is formed is prepared, and the substrate with the resist 104 is heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 105 was pressed against the resist 104 with a pressure of 10 MPa to perform imprinting (FIG. 13C). After imprinting, the substrate was cooled to room temperature and the quartz mold 105 was released (FIG. 13 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 104.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 104 was removed to expose the NiSi ₂ layer 103 (FIG. 13E).

Next, ion milling was performed for 70 seconds under conditions of Ar: 30 sccm, power of 500 W, and current of 40 mA. A pattern having an opening of 200 nm was formed in the NiSi ₂ layer 103 by ion milling. The remaining resist 104 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 13 (f)).

For comparison, a p-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and B was doped on the back surface of the p-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, a Ni layer was deposited on the surface of the substrate by a sputtering method, and annealed at 900 ° C. to form a NiSi ₂ layer having a thickness of 10 nm, thereby completing a normal Schottky solar cell.

  When the conversion efficiency of a normal Schottky solar cell and a Schottky solar cell having a nanomesh electrode were compared, an efficiency improvement of 25% was confirmed.

  In the silicon solar cell, silicide can be used as an electrode.

(Example 12)
An n-type Si substrate 111 having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared. The back surface of the n-type Si substrate 111 was doped with P by thermal diffusion to make 10 ²⁰ cm ⁻³ .

Next, 2 nm of a thermal oxide film 112 was formed on the surface of the n-type Si substrate 111. Next, an Al layer 113 was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer 114 having a thickness of 20 nm was formed on the substrate surface by vapor deposition. In this case, the substrate surface had a solar cell structure with a MIS structure of Al / SiO ₂ / Si (FIG. 14A).

Next, a solution obtained by diluting a resist 115 (THMR IP3250, Tokyo Ohka Kogyo Co., Ltd.) 1: 2 with ethyl lactate (EL) on the Al layer 114 formed on the substrate surface is spin-coated at 2000 rpm for 30 seconds. After that, the solvent was evaporated by heating on a hot plate at 110 ° C. for 90 seconds (FIG. 14B). The film thickness of the resist 115 was 150 nm. Next, a quartz mold 116 (the shape is formed in 9 cm ² ) in which a convex shape having a size of 200 nm and a height of 150 nm is prepared, and the substrate with the resist 115 is heated to 120 ° C. In this state, the one having the convex shape of the quartz mold 115 was pressed against the resist 114 with a pressure of 10 MPa to perform imprinting (FIG. 14C). After imprinting, the substrate was cooled to room temperature and the quartz mold 116 was released (FIG. 14 (d)). After imprinting, a concave shape having a size of 200 nm and a depth of 100 nm was formed on the resist 115.

Next, the resist pattern in which the concave pattern was formed was etched for 30 seconds under the conditions of O ₂ : 30 sccm, 10 mTorr, and RF power of 100 W. After O ₂ RIE, the bottom of the resist 115 was performed to expose the Al layer 114 (FIG. 14E). Next, RIE was performed for 60 seconds under the conditions of Cl ₂ : 15 sccm, Ar: 15 sccm, and RF power of 100 W. A pattern having an opening of 200 nm was formed in the Al layer 114 by RIE of chlorine gas. The remaining resist 115 was removed by oxygen ashing to complete a Schottky solar cell with a nanomesh electrode (FIG. 14 (f)).

For comparison, an n-type Si substrate having a doping concentration of 10 ¹⁶ cm ⁻³ was prepared, and P was doped on the back surface of the n-type Si substrate by thermal diffusion to prepare 10 ²⁰ cm ⁻³ . Next, a 2 nm thermal oxide film was formed on the n-type Si surface. Next, an Al layer was formed to 100 nm on the back surface of the substrate by vapor deposition, and an electrode having ohmic contact was formed on the back surface. Next, an Al layer was formed to 10 nm on the surface of the substrate by vapor deposition to complete a MIS solar cell.

  When the conversion efficiency of the metal / insulating film / semiconductor solar cell and the metal / insulating film / semiconductor solar cell having the nanomesh electrode was compared, an improvement in efficiency of 65% was confirmed.

  1,11,21,31,41,51,111 ... n-type Si substrate, 61 ... n-type GaAs substrate, 71,81 ... glass substrate, 91 ... p-type GaAs substrate, 101 ... p-type Si substrate, 2,3 , 12, 13, 22, 23, 32, 33, 42, 52, 73, 83, 102, 113, 114... Al layer.

Claims (9)

A solar cell configured by laminating a first electrode layer, a semiconductor layer, and a second electrode layer,
The semiconductor layer is made of single crystal silicon, polycrystalline silicon, amorphous silicon, or a compound semiconductor,
The first electrode layer is present on the light irradiation surface side, and is an electrode having the semiconductor layer and a Schottky wall;
The second electrode layer is on the side opposite to the light irradiation surface, and is an electrode having ohmic contact with the semiconductor layer;
The first electrode layer has a plurality of openings penetrating the first electrode layer;
The area per opening is in the range of 80 nm ^{2 to} 0.25 μm ² , and the opening ratio is in the range of 10% to 66%,
The film thickness of the first electrode layer is in the range of 5 nm to 50 nm,
The solar cell, wherein the first electrode layer and the semiconductor layer are adjacent to each other. A solar cell configured by laminating a first electrode layer, a semiconductor layer, and a second electrode layer,
The semiconductor layer is made of single crystal silicon, polycrystalline silicon, amorphous silicon, or a compound semiconductor,
A light transmissive insulating film is formed between the first electrode layer and the semiconductor layer,
The first electrode layer is present on the light irradiation surface side, and is an electrode having the semiconductor layer and a Schottky wall;
The second electrode layer is on the side opposite to the light irradiation surface, and is an electrode having ohmic contact with the semiconductor layer;
The first electrode layer has a plurality of openings penetrating the first electrode layer;
The area per opening is in the range of 80 nm ^{2 to} 0.25 μm ² , and the opening ratio is in the range of 10% to 66%,
The film thickness of the first electrode layer is in the range of 5 nm to 50 nm,
The insulating film is adjacent to the first electrode layer and the semiconductor layer;
A solar cell, wherein the insulating film has a thickness of 2 nm or less.   3. The solar cell according to claim 1, wherein an average value of a distance of a minimum portion of the metal existing between the openings is 10 nm or more and less than 200 nm. Wherein the material of the first electrode layer, Al, Ag, Au, Cu , Pt, Ni, Co, Cr, Ti, and _{PtSi, NiSi 2, CoSi 2,} MoSi 2, TiSi 2, TaSi 2, WSi 2, ZrSi _2. The solar cell according to claim 1, wherein the solar cell is a group consisting of ₂ , Pd ₂ Si, and HfSi ₂ , and is a material selected to be a Schottky junction with the photoelectric conversion layer.   The solar cell according to claim 1 or 2, wherein the opening is circular and the diameter of the opening is in the range of 10 nm to 0.5 µm. The semiconductor layer, the solar cell according to claim 1 or 2, wherein the to have the one of the layers of the p-type or n-type. It is a manufacturing method of the solar cell of Claim 1 or 2, Comprising:
Forming a semiconductor layer made of single crystal silicon, polycrystalline silicon, amorphous silicon, or a compound semiconductor ;
Forming a second electrode layer of the semiconductor layer;
Forming a first electrode layer of the semiconductor layer,
Forming a resist coating layer on the first electrode layer;
Preparing a stamper having a fine uneven pattern on the surface corresponding to the opening; and
Transferring a resist pattern to the at least part of the first electrode using the stamper;
The method of manufacturing a solar cell according to claim 1, further comprising: forming a pattern on the first electrode layer using the resist pattern as an etching mask. It is a manufacturing method of the solar cell of Claim 1 or 2, Comprising:
Forming a semiconductor layer made of single crystal silicon, polycrystalline silicon, amorphous silicon, or a compound semiconductor ;
Forming a second electrode layer of the semiconductor layer;
Forming a first electrode layer of the semiconductor layer,
Applying a resist to at least a part of the first electrode layer to form a resist coating layer;
Forming a single particle layer of nanoparticles on the surface of the resist coating layer;
Forming a resist pattern having a fine concavo-convex pattern using the single particle layer as an etching mask;
Embedding SOG in the recesses of the resist pattern;
Removing the resist of the resist pattern in which the SOG is embedded to form a hole pattern of the SOG;
The method for manufacturing a solar cell according to claim 1, further comprising: forming a pattern on the first electrode layer using the hole pattern as an etching mask. It is a manufacturing method of the solar cell of Claim 1 or 2, Comprising:
Forming a semiconductor layer made of single crystal silicon, polycrystalline silicon, amorphous silicon, or a compound semiconductor ;
Forming a second electrode layer of the semiconductor layer;
Forming a first electrode layer of the semiconductor layer,
Forming a resist coating layer on the first electrode layer;
Forming an SOG film on the resist coating layer;
Generating a dot-like microdomain of a block copolymer film on the surface of at least a part of the SOG film;
Etching the microdomains of the block copolymer film to generate a dot pattern;
Etching the SOG film using the dot pattern as an etching mask to form an SOG dot pattern;
Etching the resist coating layer using the SOG dot pattern as an etching mask to form a resist pillar pattern;
Embedding SOG in the recesses of the resist pillar pattern;
Removing the resist pillar pattern resist embedded with the SOG to form a SOG hole pattern;
The method for manufacturing a solar cell according to claim 1, further comprising: forming a pattern on the first electrode layer using the hole pattern as an etching mask.

Images