JP5131418B2 - Surface structure with improved transmittance - Google Patents

Description

  The present invention relates to a transmittance-improving surface structure, for example, a transmittance-improving surface structure that can be applied to the surface of a solar cell or the like to improve the transmittance and improve the light utilization efficiency.

In the field of optics, there is known a technique for improving the transmittance by preventing reflection by a multilayer film or a moth-eye structure (Patent Document 1).
JP 2003-222701 A

  However, the multilayer film and the moth-eye structure have a problem that the performance deteriorates when they deviate from the design wavelength and the design incident angle due to the wavelength dependency and the incident angle dependency. In addition, the multilayer film requires many steps, and the moth-eye structure has to be manufactured with a high aspect ratio (depth / pitch is high) with a fine structure with a wavelength less than the wavelength, which is relatively difficult to manufacture.

  The present invention has been made in view of such problems of the prior art, and the object thereof is to provide a periodic structure on the surface of an optical component on which light is incident so as to improve the transmittance and use efficiency of light. The present invention relates to a surface structure with improved transmittance.

The surface-enhanced surface structure of the present invention that achieves the above object includes a basic unit in which a main groove having a rectangular cross section is formed between main linear protrusions having a rectangular cross section on the surface of an optical component on which light is incident. In a periodic structure that is arranged periodically and continuously in a direction orthogonal to
Each main linear protrusion is formed with a sub-groove having a rectangular cross section with a reduced width.

  In this case, a sub-sub-groove having a rectangular cross-section with at least a reduced width may be formed on each of the sub-line-like protrusions on both sides of the sub-groove.

  Furthermore, sub-sub-sub-grooves having a rectangular cross-section with a further reduced width may be formed in each of the sub-sub-linear projections on both sides of the sub-sub-groove.

  Furthermore, you may make it have the surface structure obtained by performing the operation which provides the same groove | channel in each formed linear protrusion further once or more.

  Further, the depth of the sub-groove may be shallower than the main groove.

Another surface-enhancing surface structure according to the present invention is that a basic unit in which a main line-shaped protrusion having a rectangular cross section is formed between main grooves having a rectangular cross section on the surface of an optical component on which light is incident is orthogonal to the groove and the protrusion. In the periodic structure that is arranged periodically and continuously in the direction of
Each main groove is formed with a sub-linear protrusion having a rectangular cross section with a reduced width.

  In this case, sub-sub-linear protrusions having a rectangular cross section with at least a reduced width may be formed in each of the sub-grooves on both sides of the sub-line protrusion.

  Furthermore, a sub-sub-sub-linear protrusion having a rectangular cross section with at least a reduced width may be formed in each of the sub-sub-grooves on both sides of the sub-sub-line protrusion.

  Furthermore, it may have a surface structure obtained by further performing the operation of providing a similar linear protrusion in each of the formed grooves one or more times.

  Further, the height of the sub linear protrusion may be lower than the main linear protrusion.

  In addition, the pitch of the basic unit may be equal to or greater than the use wavelength.

  The present invention includes an optical component having the above-described transmittance improving surface structure.

  According to the transmittance improving surface structure of the present invention described above, it is possible to improve the light utilization efficiency by improving the transmittance of an optical component on which light is incident with a simple structure. The transmittance-improving surface structure of the present invention can be easily produced with few steps, and is easy to produce because the period is relatively long and the aspect ratio is relatively small.

  The surface-enhanced surface structure of the present invention relates to the structure of the surface of an optical component on which light is incident (including a part that takes in light such as a solar cell), and the basic structure is one direction (one-dimensional) with a rectangular cross section. ) Periodic structure.

  First, with reference to FIG. 1 for explaining the transmittance-enhancing surface structure of the present invention, the way of illustration in FIG. 1 will be explained. The columns (a), (b), and (c) are taken in the horizontal direction, and the columns (1), (2-1), and (2-2) are taken in the vertical direction. 1 is viewed at the intersection of the horizontal column and the vertical column, and is viewed as (1) in (a), (2-1) in (a), and the like. In each of (a), (b), and (c), (1) is a plan view, (2-1) and (2-2) are cross-sectional views, and (1) in (a) of FIG. (2-2) is a comparative example of the present invention, and (1) to (2-2) in FIG. 1 (b) and (1) to (2-2) in (c) are transmissions of the present invention. It is an example of a surface improvement surface structure. The plan view is taken on the xy plane, and the sectional view is taken on the xz plane. Hereinafter, the surface structure of FIG. 1 will be described in order.

FIG. 1A is a comparative example of the present invention, and is a basis for explaining the transmittance-improving surface structure of the present invention (FIGS. 1B and 1C). This surface structure is a structure in which basic units of pitch (period) Λ are periodically arranged in one direction (x direction) on the surface of the optical component. When the refractive index of the optical component is n ₂ and the refractive index of the medium covering the surface is n ₁ and n ₁ <n ₂ , this periodic structure is called a groove type (concave type). When the refractive index is n ₁ , the refractive index of the medium covering the surface is n ₂ , and n ₁ > n ₂ , this periodic structure is called a protrusion type (convex type). In the case of the groove type, a groove 2 having a rectangular cross section is arranged between the linear protrusions 1 and 1 whose basic unit of the periodic structure is a rectangular cross section, and in the case of the protrusion type, a linear protrusion having a rectangular cross section. Grooves 1 and 1 having a rectangular cross section are disposed on both sides of 2. Therefore, reference numeral 1 is a linear protrusion in the case of a groove type, and a groove in the case of a protrusion type. Reference numeral 2 denotes a groove in the case of a groove type, and a linear protrusion in the case of a protrusion type. The same applies to the following symbols, 11, 12, 111, and 112.

  1B and 1C, the plan view of (1) is common, and (2-1) and (2-2) are cross-sectional views of different structures.

  In the example of the surface improvement surface structure of the present invention of FIG. 1B, in the case of the groove type, a finer groove 12 is formed on the surface of the linear protrusion 1 having the structure of FIG. Are formed in parallel with each other, and fine linear protrusions 11 and 11 are formed on both sides of the groove 12. That is, as in FIG. 1A, as a basic unit of the periodic structure, a main groove 2 having a rectangular cross section is formed between main linear protrusions 1 and 1 having a rectangular cross section, and the main linear protrusions 1 and 1 are formed. Sub-grooves 12 having at least a reduced width are formed in each.

  In the case of the projection type, finer linear projections 12 are provided in parallel with the grooves 1 on the surfaces of the grooves 1 and 1 arranged on both sides of the linear projection 2 having the configuration shown in FIG. Fine grooves 11 and 11 are formed on both sides of the projection 12. That is, as in FIG. 1A, as a basic unit of the periodic structure, main grooves 1 and 1 having a rectangular cross section are formed on both sides of a main linear protrusion 2 having a rectangular cross section. The sub-line-shaped protrusions 12 having at least a reduced width are formed.

  The difference in the configuration between (2-1) and (2-2) in FIG. 1B is that the depth (height) of the sub-groove 12 (sub-linear protrusion 12) is the main groove 2 (main linear protrusion 2). ) It is a difference whether it is shallower or the same, and any configuration may be taken.

  The main unit of the basic unit in which the main groove (main line protrusion) 2 having a rectangular cross section is formed between the main line protrusions (main grooves) 1 and 1 having a rectangular cross section in FIG. The transmissivity-improving surface structure of the present invention in which the sub-grooves (sub-linear protrusions) 12 having at least a reduced width are formed in the protrusions (main grooves) 1 and 1 will be referred to as a surface structure with one deformation. The surface structure of (a) is referred to as a surface structure without deformation.

  A surface structure having the same deformation as the one-time surface structure of FIG. 1B is the two-time surface structure of FIG. That is, in the case of the groove type, the surface structure is formed by forming the sub-sub-groove 112 having at least a reduced width on each of the sub-linear protrusions 11 on both sides of the sub-groove 12 having the configuration shown in FIG. . In the case of the protrusion type, a surface structure in which the sub-sub linear protrusion 112 having at least a reduced width is formed in each of the sub-grooves 11 on both sides of the sub-linear protrusion 12 having the configuration shown in FIG. It is. This will be referred to as a surface structure with two deformations. This modified two-time surface structure is also an example of the surface structure with improved transmittance according to the present invention.

  The difference in the configuration between (2-1) and (2-2) in FIG. 1C is that the depth (height) of the sub-sub-groove 112 (sub-sub-line protrusion 112) is sub-groove 12 (sub-line). 1 (c), (2-2), the main groove 2 (main linear protrusion 2) and the sub groove 12 (sub line). The protrusions 12) and the sub-sub-grooves 112 (sub-sub-line protrusions 112) have the same depth (height).

  In each of the sub-sub linear projections 111 on both sides of the sub-sub-groove 112 in FIG. 1C (sub-sub-grooves 111 on both sides of the sub-sub-linear projection 112), at least the sub-sub-sub-groove reduced in width in the same manner. The surface structure formed with (sub-sub-sub-sub linear protrusions) will be referred to as a surface structure with three deformations. This modified three-time surface structure is also an example of the transmittance-improving surface structure of the present invention.

  Hereinafter, similarly, a surface structure having four or more deformations is obtained, and these are the surface structure with improved transmittance of the present invention.

  Now, it will be described on the basis of an embodiment that the transmittance of incident light is improved by using the surface improvement structure of the present invention that has been modified one or more times as described above.

  FIG. 2 is a diagram showing the incident angle dependence of the efficiency of all transmitted light (total transmitted light efficiency) when entering the plane of a medium (Si) having a refractive index of 3.6 from the air as a reference for comparison. . The polarization angle of incident light is 45 °. Here, as shown in FIG. 3, the incident angle is an angle between the normal line (z axis) and incident light when the plane on which the light ray enters is an xy plane, and the polarization angle is When a plane perpendicular to the xy plane and including incident light is defined as an “incident surface”, it is an angle formed by the polarization vector (electric vector) of the incident light and the “incident surface”. The azimuth angle of incident light on the surface of the periodic structure that emerges later is an angle formed by the incident surface with respect to the periodic direction when the periodic direction is the x direction.

  FIG. 4 shows a modified one-time transmittance-enhancing surface structure of the present invention (in the case of the groove type (2-1) in FIG. 1 (b)) and a comparative example (no deformation: (a) in FIG. 1). The incident angle dependence of the total transmitted light efficiency when the pitch Λ of the basic unit is changed is shown. The transmitted total light efficiency is shown as a difference with respect to the transmitted total light efficiency when entering the plane of FIG. The ratio of the width in the basic unit is 1: 1: 1: 3: 1: 1: 1 in the case of one modification of the present invention, and 1: 1: 1 in the case of no modification of the comparative example. The depth of the deepest portion of the groove is 0.3 times the pitch Λ, and the depth of the sub-groove 12 in the case of one modification of the present invention is 1/3 of the deepest portion. Also in this case, it is the transmitted total light efficiency when entering from the air into the medium (Si) having a refractive index of 3.6, and the wavelength used is λ. The azimuth angle of incident light is 0 ° and the polarization angle is 45 °. For example, “deformation once 5” in FIG. 4 means the case of (2-1) structure in FIG. 1B and Λ / λ = 5.

  From FIG. 4, it can be seen that the total transmitted light efficiency is higher in the single deformation as a whole than in the case without the deformation. It can be seen that the smaller the basic unit pitch Λ with respect to the wavelength λ used, the higher the total transmitted light efficiency tends to be higher within an incident angle of about 60 °, although this is not necessarily the order. In other words, the smaller the basic unit pitch Λ with respect to the wavelength λ used, the higher the transmitted total light efficiency tends to be higher, but there is a deformation regardless of the basic unit size (transmission-improving surface structure of the present invention). It can be seen that there is an effect of improving the transmittance as compared with the case without the.

  Next, FIG. 5 to FIG. 10 show the incident angle dependence of the total luminous efficiency of the groove type and the protrusion type of the deformation type and the deformation type twice as compared with the case where Λ / λ = 3. The transmitted total light efficiency is shown as a difference with respect to the transmitted total light efficiency when entering the plane of FIG. Both are the total transmitted light efficiency when entering the medium (Si) having a refractive index of 3.6 from the air, and the polarization angle is 45 °.

  5 and 6 show the case of the groove type and the protrusion type without deformation, respectively. FIG. 5 shows the depth of the deepest part of the groove with respect to the operating wavelength λ is 0.60, and FIG. 6 shows the linear protrusion with respect to the operating wavelength λ. The height of the highest part is 0.55, and the depth of these deepest parts, the figure of the highest part of the height is the total transmitted light efficiency when the depth or height is increased from the smaller one Is the depth or height giving the peak first (see FIG. 17). The same applies to FIGS. 7 to 10 below.

  FIGS. 7 and 8 show the case of a single deformation, a groove type and a protrusion type. FIG. 7 shows the depth of the deepest part of the groove with respect to the operating wavelength λ is 0.70, and FIG. The height of the highest part of the protrusion is 0.85.

  FIGS. 9 and 10 show two cases of deformation, a groove type and a protrusion type. FIG. 9 shows the depth of the deepest part of the groove with respect to the operating wavelength λ is 0.70, and FIG. The height of the highest part of the protrusion is 0.80.

  The width ratio in the basic unit is 1: 1: 1 without deformation, 1: 1 deformation, 1: 1: 1: 3: 1: 1: 1, 1: 1 deformation, and 1: 1: 1. : 3: 1: 1: 1: 9: 1: 1: 1: 1: 3: 1: 1: 1 and the depth of the groove (the height of the linear protrusion) is one deformation, and the shallow groove (low) (Linear protrusion) is 1/3 of the deepest part (highest part), deformation is 2 times, and the second shallowest groove (low linear protrusion) is 1/3 of the deepest part (highest part), and the first shallowest groove ( (Low linear protrusion) is 1/9 of the deepest part (highest part).

  Next, in the case of Λ / λ = 1, diagrams similar to FIGS. 5 to 10 are shown in FIGS. Again, the transmitted total light efficiency is shown as the difference to the transmitted total light efficiency when incident on the plane of FIG. Both are the total transmitted light efficiency when entering the medium (Si) having a refractive index of 3.6 from the air, and the polarization angle is 45 °.

  11 and 12 show the case of the groove type and the protrusion type without deformation, respectively, FIG. 11 shows the depth of the deepest part of the groove with respect to the use wavelength λ is 0.20, and FIG. 12 shows the linear protrusion with respect to the use wavelength λ. The depth of the deepest part, the figure of the height of the deepest part, the figure of the height of the highest part is the transmitted total light efficiency when the depth or height is increased from the smaller one Is the depth or height giving the peak first (see FIG. 18). The same applies to FIGS. 13 to 16 below.

  FIGS. 13 and 14 show the case of a single deformation, a groove type and a protrusion type. FIG. 13 shows the depth of the deepest part of the groove with respect to the operating wavelength λ is 0.30, and FIG. The height of the highest part of the protrusion is 0.25.

  FIGS. 15 and 16 show two cases of deformation, a groove type and a protrusion type. FIG. 15 shows the depth of the deepest part of the groove with respect to the operating wavelength λ is 0.40, and FIG. The height of the highest part of the protrusion is 0.30.

  The width ratio in the basic unit is 1: 1: 1 without deformation, 1: 1 deformation, 1: 1: 1: 3: 1: 1: 1, 1: 1 deformation, and 1: 1: 1. : 3: 1: 1: 1: 9: 1: 1: 1: 1: 3: 1: 1: 1 and the depth of the groove (the height of the linear protrusion) is one deformation, and the shallow groove (low) (Linear protrusion) is 1/3 of the deepest part (highest part), deformation is 2 times, and the second shallowest groove (low linear protrusion) is 1/3 of the deepest part (highest part), and the first shallowest groove ( (Low linear protrusion) is 1/9 of the deepest part (highest part).

  Next, d is the deepest part (highest part) of the groove (linear protrusion), and the dependency of the transmitted light total light efficiency (transmitted total light efficiency) on the deepest part (highest part) d is Λ / λ = 3. The case of 1 is shown in FIGS. 17 and 18, respectively. In FIG. 17 and FIG. 18, “concave” and “convex” mean a groove type and a protrusion type, respectively, “0”, “1”, and “2” after them are no deformation, one deformation, and two deformations, respectively. Means times. The width ratio in the basic unit is 1: 1: 1 without deformation, 1: 1 deformation, 1: 1: 1: 3: 1: 1: 1, 1: 1 deformation, and 1: 1: 1. : 3: 1: 1: 1: 9: 1: 1: 1: 3: 1: 1: 1.

  From the results shown in FIGS. 5 to 18, the first and second modified surface structures of the present invention are comparative examples without deformation regardless of the azimuth angle regardless of the azimuth. It can be seen from (a) of 1 that the total transmitted light efficiency is high.

  Next, two optimized examples are shown. FIG. 19 shows the incident angle dependence of the transmitted total light efficiency of one example. The transmitted total light efficiency is shown as a difference with respect to the transmitted total light efficiency when entering the plane of FIG. This example is a groove type of Λ / λ = 1, and it is assumed that the light is incident on a medium (Si) having a refractive index of 3.6 from the air with a polarization angle of 45 ° by two deformations. The depth of the deepest part is 0.95, and the value of the depth of the deepest part is the depth at which the total transmitted light efficiency gives the second peak when the depth is increased from the smaller side, The ratio of width in the basic unit is 1: 1: 1: 3: 1: 1: 1: 9: 1: 1: 1: 3: 1: 1: 1 and the groove depth is the second The shallow groove is 1/3 of the deepest part, and the shallowest groove is 1/9 of the deepest part.

  FIG. 20 shows the incident angle dependence of the total transmitted light efficiency similar to FIG. 19 of another example. In this example, a projection type with Λ / λ = 1 is assumed, and in a single deformation, the light is incident on a medium (Si) having a refractive index of 3.6 from the air at a polarization angle of 45 °, and is linear with respect to the used wavelength λ. The height of the protrusion is 0.289 at the highest part and 0.09826 for the second lowest linear protrusion, and the height value of the highest part is transmitted when the height is increased from the smaller one. The total light efficiency is the depth that gives the first peak, and the ratio of widths in the basic unit is 0.1156: 0.1008: 0.1156: 0.3200: 0.1156: 0.1008: 0.1156 It is.

  As mentioned above, although the transmittance | permeability improvement surface structure of this invention has been demonstrated based on the Example, this invention is not limited to these Examples, A various deformation | transformation is possible. Further, the transmittance-improving surface structure of the present invention can be relatively easily produced by using photolithography or embossing. Further, the transmittance improving surface structure of the present invention can be applied not only to the surface of an optical component such as a lens, but also to the surface of a transparent or translucent component (for example, a solar cell) that requires light to enter efficiently. is there.

It is a figure for demonstrating the transmittance | permeability improvement surface structure of this invention. It is a figure which shows the incident angle dependence of the transmission total light efficiency when injecting into the plane of the medium of refractive index 3.6 from the air as a reference of comparison. It is a figure for demonstrating an incident angle, a polarization angle, and an azimuth angle. It is a figure which shows the incident angle dependence of the transmission total light efficiency when changing the pitch of the basic unit of the deformation | transformation 1 time of this invention and the basic unit of a comparative example. It is a figure which shows the incident angle dependence of groove-shaped transmitted total light efficiency without a deformation | transformation in case of (LAMBDA) / (lambda) = 3. It is a figure which shows the incident angle dependence of protrusion type | mold transmission total light efficiency without a deformation | transformation in case of (LAMBDA) / (lambda) = 3. It is a figure which shows the incident angle dependence of groove-shaped transmitted total light efficiency by one deformation | transformation in case of (LAMBDA) / (lambda) = 3. It is a figure which shows the incident-angle dependence of protrusion type | mold transmission total light efficiency by 1 deformation | transformation in case of (LAMBDA) / (lambda) = 3. It is a figure which shows the incident angle dependence of groove-shaped transmitted total light efficiency in 2 deformation | transformation in case of (LAMBDA) / (lambda) = 3. It is a figure which shows the incident angle dependence of protrusion type | mold transmission total light efficiency in 2 deformation | transformation in case of (LAMBDA) / (lambda) = 3. It is a figure which shows the incident angle dependence of groove-shaped transmitted total light efficiency without a deformation | transformation in case of (LAMBDA) / (lambda) = 1. It is a figure which shows the incident angle dependence of protrusion type | mold transmission total light efficiency without a deformation | transformation in case of (LAMBDA) / (lambda) = 1. It is a figure which shows the incident angle dependence of groove-shaped transmitted total light efficiency by one deformation | transformation in case of (LAMBDA) / (lambda) = 1. It is a figure which shows the incident angle dependence of 1st modification | transformation in the case of (LAMBDA) / (lambda) = 1 and protrusion type | mold transmission total light efficiency. It is a figure which shows the incident angle dependence of groove-shaped transmitted total light efficiency in 2 deformation | transformation in case of (LAMBDA) / (lambda) = 1. It is a figure which shows the incident angle dependence of the projection type | mold transmission total light efficiency by the deformation | transformation 2 times in the case of (LAMBDA) / (lambda) = 1. It is a figure which shows the dependence of the permeation | transmission total light efficiency with respect to the deepest part (highest part) of a groove | channel (linear protrusion) in the case of (LAMBDA) / (lambda) = 3. It is a figure which shows the dependence of the permeation | transmission total light efficiency with respect to the deepest part (highest part) of a groove | channel (linear protrusion) in case of (LAMBDA) / (lambda) = 1. It is a figure which shows the incident angle dependence of the transmission total light efficiency of one Example optimized. It is a figure which shows the incident angle dependence of the transmission total light efficiency of the other Example optimized.

Explanation of symbols

1 ... Linear protrusion (groove)
2 ... Groove (Linear protrusion)
11 ... Sub linear protrusion (sub groove)
12 ... Sub-groove (sub-linear protrusion)
111 ... Sub-sub linear projection (sub-sub-groove)
112 ... minor minor groove (minor minor linear projection)

Claims (10)

A main groove having a rectangular cross section is formed between the main linear protrusions having a rectangular cross section on the surface of the optical component on which light is incident, and a basic unit formed with a width ratio of protrusion: groove: protrusion = 1: 1: 1 And in a periodic structure that is arranged periodically and continuously in a direction perpendicular to the groove,
A sub-groove having a rectangular cross section with a width reduced to 1/3 of the width of the protrusion is formed in the center of each main linear protrusion,
Moreover the reduced cross section rectangular sub-sub-groove Toru you characterized in that is formed over rate improving surface structure at least the width in the sub linear projections each of both sides of the minor groove. Transmittance improved surface structure according to claim 1, characterized in that the further reduced cross-sectional rectangular sub-sub-sub-grooves at least width is formed in the sub-sub-linear projections each of both sides of the sub-sub-groove. 3. The transmittance improving surface according to claim 2, wherein each of the sub-sub-sub-linear projections on both sides of the sub-sub-sub-groove is formed with a sub-sub-sub-sub-groove having a rectangular cross section with a further reduced width. Construction. The surface structure for improving transmittance according to any one of claims 1 to 3 , wherein the depth of the sub-groove is smaller than that of the main groove. A main linear protrusion having a rectangular cross section is formed between the main grooves having a rectangular cross section on the surface of the optical component on which light is incident, and a basic unit formed with a width ratio of groove: protrusion: groove = 1: 1: 1 And in a periodic structure that is arranged periodically and continuously in a direction perpendicular to the protrusions,
In the center of each main groove, a sub-line-shaped protrusion having a rectangular cross section whose width is reduced to 1/3 of the width of the groove is formed,
The further reduced cross-sectional rectangular sub-sub-linear projection Toru characterized in that is formed over rate improving surface structure at least the width to the minor groove of each of both sides of the sub linear protrusions. 6. The transmissivity-improving surface structure according to claim 5, wherein each of the sub-sub-grooves on both sides of the sub-sub-line protrusion is formed with a sub-sub-sub-line-shaped protrusion having a rectangular cross section with a further reduced width. . 7. The transmittance according to claim 6, wherein each of the sub-sub-sub-grooves on both sides of the sub-sub-sub-line-like protrusion is formed with a sub-sub-sub-sub-sub-line-like protrusion having a rectangular cross section with a further reduced width. Improved surface structure. The transmittance improving surface structure according to any one of claims 5 to 7 , wherein a height of the sub linear protrusion is lower than the main linear protrusion. The transmittance improving surface structure according to any one of claims 1 to 8 , wherein the pitch of the basic unit is not less than a used wavelength. An optical component comprising the transmittance improving surface structure according to any one of claims 1 to 9 .

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