TWI429099B - Substrate with broadband light scattering and method of fabricating the same - Google Patents

Description

Substrate with broadband light scattering function and method of manufacturing same

The present invention relates to a substrate having a broadband light scattering function and a method of fabricating the same. A substrate having a broadband light scattering function according to the present invention comprises a thin plate, an adhesive layer, a plurality of scattering particles, and a transparent conductive layer. A method of fabricating a substrate having a broadband light scattering function according to the present invention forms the transparent conductive layer by a sputtering process.

The conductive film used in the fabrication of tantalum thin film solar cells is a transparent conductive oxide (TCO). Common TCO host materials such as indium oxide (In ₂ O ₃ ), tin oxide (SnO ₂ ), and zinc oxide (ZnO), etc., which are originally transparent oxide semiconductors, can greatly enhance their conductivity by doping with impurities. Both transparent and conductive. At present, the front electrode TCO used in the ruthenium film is mainly fluorine-doped tin oxide (FTO) with a surface roughness structure, and the back electrode is aluminum-doped zinc oxide (aluminum- Doped zinc oxide, AZO) is mostly.

U.S. Patent No. 7,179, 527, and U. The optical path length increases the light absorption to increase the photocurrent intensity, further improving the photoelectric conversion efficiency. Both of the above patents disclose a substrate having a transparent conductive oxide film, which can be scattered in the wavelength range of 400 nm to 800 nm.

The most widely used TCO glass is the product number Asahi-U produced by Asahi Glass Company of Japan. The glass product is subjected to atmospheric pressure chemical vapor deposition (APCVD) at a temperature of 400 ° C or higher, and a precursor material containing tin (Sn) and a trace amount of fluorine (F) is reacted with O ₂ /H ₂ O to deposit on the surface of the glass. A layer of fluorine-doped tin oxide (FTO) film having a thickness of about 800 nm. And it has a surface roughness to increase the effect of light scattering. The optical properties of the Asahi-U glass revealed that the glass had a transmittance of about 80% in the visible wavelength range. After deducting about 12% of the reflection, it was found that there was still about 7 to 8% of the absorption loss. In addition, most of the ideal parts of Asahi-U glass for light scattering are concentrated in the short wavelength range from 350 nm to 550 nm.

The TCO glass produced by Oerlikon is a boron-doped zinc oxide (B-doped ZnO, BZO) by introducing diethyl zinc, water and a dopant gas B ₂ H ₆ into a low pressure chemical vapor deposition (LPCVD) reactor. The film layer, in fact, in addition to the TCO material is different from Asahi-U, its optical properties are similar to Asahi-U. However, in order to enhance the scattering characteristics of light in the long wavelength range, this series of TCOs must be achieved by increasing the thickness of the TCO film layer to enlarge the surface crystal grain boundaries. Such an increase in film thickness to enhance the scattering characteristics of light in a long wavelength range is often accompanied by a problem of a decrease in light transmittance due to thickening of the TCO layer.

Germany's Von Ardenne's development strategy is to use a sputtering method to obtain aluminum-doped zinc oxide (AZO) film with high conductivity and high optical penetration through process conditions adjustment, and then wet chemical etching. The surface of the film is etched, and the film of different surface morphology is obtained by controlling the sputtering condition and the etching condition to enhance the scattering effect on light of different wavelengths. The surface roughened aluminum-doped zinc oxide (AZO) film obtained by a wet etching process is subjected to a sputtering method, and the surface roughening morphology is limited by the crystal structure of the TCO film before acid etching, including crystal orientation. ), grain size distribution and concentration of dopants such as Al or Ga, and factors such as the type of acid used, such as etching characteristics with HCl. In order to increase the scattering characteristics of the long-wavelength optical band, the sputter film must be thick and then applied to a long-time wet etching process to cause a large etching structure on the surface of the TCO film. The above method is obviously not economical, because in addition to increasing the sputtering time, it also increases the expensive target wear.

The above commercial TCO glass still has many shortcomings in technical specifications:

1. As with Asahi-U glass, scattering of long-wavelength light with wavelengths greater than 600 nm is clearly insufficient. In fact, the high absorption coefficient (α=10 ⁴ ~10 ⁵ /cm) of the short-wavelength light (400-500 nm) with amorphous germanium material does not require the roughening structure of the TCO surface, and can be used in the amorphous germanium film element. The surface of the intrinsic i-layer has a little depth (less than 0.1 μm) for most of the absorption. In contrast, for long-wavelength light (greater than 600 nm) that can penetrate deeper than the amorphous germanium layer, the light scattering caused by the surface roughness of Asahi-U glass can hardly play a role in this range.

2. The SnO ₂ film is susceptible to the chemical action of H ₂ or SiH ₄ plasma. When the amorphous germanium film is formed by plasma-assisted chemical vapor deposition, the fluorine-doped tin oxide (FTO) film is exposed to hydrogen for a long time. When the ion is subjected to a plasma process, the formation of the Sn metal reduction layer is liable to be blackened and the light transmittance is lowered.

The first disadvantage described above is particularly important on a new generation of amorphous germanium/microcrystalline tandem cells that provide high cell efficiency values. Since the optical energy gap of the microcrystalline layer is at 1.1 eV, it is designed to absorb solar energy in the wavelength range of 700 nm to 1200 nm that the amorphous cell cannot absorb. However, since the absorption coefficient of the microcrystalline germanium is about one tenth of that of the amorphous germanium, a thick film thickness (several μm) is required, which requires another high speed different from the 13.56 Mz RF frequency. The main reason for long film plasma sources (such as 40MHz very high frequency (VHF)). The focus is on the TCO glass at the current stage, such as Asahi-U, and even the development strategy of Oerlikon and Von Ardenne in Germany is to use the TCO glass which is first etched by sputtering. The scattering ability in the wavelength range from 700 nm to 1200 nm is very limited. .

Further, the above-mentioned second disadvantage is that a thin film of SnO ₂ H ₂ or SiH ₄ more non-reducing plasma resistance, light transmittance is displayed SnO ₂ film layer decreased phenomenon under H ₂ plasma exposure.

At present, the TCO available in the market and in the research and development stage cannot effectively improve the conversion efficiency of the multi-layered tantalum thin film solar cells, resulting in the cost reduction of the tantalum thin film solar cells of single junction, double junction and triple junction. And the conversion efficiency can not be improved, which in turn leads to the global development of the thin film solar cell industry.

Accordingly, it is an object of the present invention to provide a substrate having a broadband light scattering function and a method of fabricating the same. A substrate having a broadband light scattering function according to the present invention comprises a thin plate, an adhesive layer, a plurality of scattering particles, and a transparent conductive layer. And in particular, the method of fabricating a substrate having a broadband light scattering function according to the present invention covers the transparent conductive layer on a light-emitting surface of the plurality of scattering particles and one of the thin plates by a sputtering process. The substrate having the broadband light scattering function according to the present invention can effectively improve the efficiency of the tantalum film solar cell. This novel substrate with broadband light scattering function is more effective in improving the efficiency of tandem tantalum film solar cells due to the increased long-wavelength light scattering capability.

According to a preferred embodiment of the present invention, a method of fabricating a substrate having a broadband light scattering function begins by preparing a thin plate formed of a first material. The thin plate has a light incident surface and a light emitting surface opposite to the light incident surface. Next, in accordance with the method of the present invention, a plurality of scattering particles formed from a second material are prepared, wherein the plurality of scattering particles have a distribution of particle size changes. Then, the plurality of scattering particles are fixed on the light-emitting surface of the thin plate according to the method of the present invention, wherein the plurality of scattering particles are dispersed on the light-emitting surface of the thin plate. Finally, the method according to the present invention covers a plurality of transparent particles by covering a plurality of scattering particles and the light-emitting surface by a sputtering process.

Thereby, when a sunlight illuminates the light incident surface and the plurality of scattering particles dispersed on the light exiting surface, a distribution of the particle size change corresponds to a broadband range of light scattering from the light emitting surface to the transparent conductive Floor.

In a practical application, the step of fixing the plurality of scattering particles on the light-emitting surface of the thin plate may adhere an adhesive layer to the light-emitting surface by a sol-gel method. And the adhesive layer is used for fixing the plurality of scattering particles on the light emitting surface.

In one embodiment, the change in particle size of the plurality of scattering particles is in the range of 0.05 to 20 μm. In practical applications, the variation of the particle size of the plurality of scattering particles may depend on the wavelength bandwidth of the desired scattering.

In a specific embodiment, the first material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). One of the groups.

In a specific embodiment, the second material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), and the like. One of a group consisting of a mixture of compounds.

In one embodiment, the transparent conductive layer may be composed of a transparent conductive oxide such as ITO, AZO, BZO, GZO (gallium-doped zinc oxide), FTO, and various transparent conductive oxide materials.

A substrate having a broadband light scattering function according to a preferred embodiment of the present invention includes a thin plate formed of a first material, an adhesive layer, a plurality of scattering particles formed of a second material, and a Transparent conductive layer. The thin plate formed by the first material has a light incident surface and a light emitting surface opposite to the light incident surface. And the adhesive layer is attached to the light emitting surface of the thin plate. The plurality of scattering particles are dispersed on the light emitting surface of the thin plate and fixed on the light emitting surface by the adhesive layer. The plurality of scattering particles have a distribution of particle size changes. The transparent conductive layer covers the adhesive layer and the plurality of scattering particles.

Thereby, when a sunlight illuminates the light incident surface and the plurality of scattering particles dispersed on the light exiting surface, a distribution of the particle size change corresponds to a broadband range of light scattering from the light emitting surface to the transparent conductive Floor.

In one embodiment, the change in particle size of the plurality of scattering particles is in the range of 0.05 to 20 μm. In practical applications, the variation of the particle size of the plurality of scattering particles may depend on the wavelength bandwidth of the desired scattering.

In a specific embodiment, the first material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). One of the groups. And, the second material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), and a mixture of the above compounds. One of the groups.

In one embodiment, the transparent conductive layer may be formed of a transparent conductive oxide such as ITO, AZO, BZO, GZO, FTO, and various transparent conductive oxide materials.

The advantages and spirit of the present invention will be further understood from the following detailed description of the invention.

The preferred embodiments of the present invention will be described in detail in the following description.

Referring to FIG. 1A to FIG. 1C, the drawings schematically illustrate a method of fabricating a substrate 1 having a broadband light scattering function according to a preferred embodiment of the present invention.

As shown in FIG. 1A, firstly, according to the manufacturing method of the present invention, a thin plate 12 formed of a first material is prepared, wherein the thin plate 12 has a light incident surface 122 and a light emitting surface opposite to the light incident surface. 124.

Next, the manufacturing method according to the present invention produces a plurality of scattering particles 16 formed of a second material, wherein the plurality of scattering particles 16 have a distribution of particle size changes.

Then, as shown in FIG. 1B, the manufacturing method according to the present invention fixes the plurality of scattering particles 16 on the light-emitting surface 124 of the thin plate 12, wherein the plurality of scattering particles 16 are dispersed on the thin plate 12 On the light surface 124.

Finally, as shown in FIG. 1C, the manufacturing method according to the present invention covers a plurality of transparent particles 18 and the light-emitting surface 124 with a transparent conductive layer 18 by a sputtering process.

Thereby, when a sunlight illuminates the light incident surface 122 and the plurality of scattering particles 16 dispersed on the light exit surface 124, a distribution of the particle size change corresponds to a broadband range of light passing through the light exit surface 124. The scattering particles 16 are scattered to the transparent conductive layer 18.

As shown in FIG. 1B, in a practical application, the step of fixing the plurality of scattering particles 16 on the light-emitting surface 124 of the thin plate may be performed on the light-emitting surface by a sol-gel method. An adhesive layer 14 is attached to the upper layer. And the adhesive layer 14 can be used to fix the plurality of scattering particles on the light-emitting surface.

In one embodiment, the change in particle size of the plurality of scattering particles is in the range of 0.05 to 20 μm. In practical applications, the variation of the particle size of the plurality of scattering particles 16 may depend on the wavelength bandwidth of the desired scattering.

In a specific embodiment, the first material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). One of the groups.

In a specific embodiment, the second material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), and the like. One of a group consisting of a mixture of compounds.

In one embodiment, the transparent conductive layer 18 may be composed of a transparent conductive oxide such as ITO, AZO, BZO, GZO, FTO, and various transparent conductive oxide materials.

In a practical application, according to the method for manufacturing a substrate having a broadband light scattering function according to the present invention, after the transparent conductive layer 18 (for example, AZO) is sputtered, the surface of the transparent conductive layer 18 may be additionally etched to increase the The roughness of the surface of the transparent conductive layer 18. Increasing the roughness of the surface of the transparent conductive layer 18 can reduce the reflection of incident light and simultaneously increase the optical path length of the photon to increase the light absorption to enhance the photocurrent intensity, further improving the photoelectric conversion efficiency.

Referring to FIG. 2, FIG. 2 is a schematic diagram showing a substrate 2 having a broadband light scattering function according to a preferred embodiment of the present invention.

As shown in FIG. 2, the substrate 2 having the broadband light scattering function according to the present invention comprises a thin plate 22 formed of a first material, an adhesive layer 24, a plurality of scattering particles 26 formed of a second material, and A transparent conductive layer 28.

Also shown in FIG. 2, the thin plate 22 formed of the first material has a light incident surface 222 and a light exit surface 224 opposite to the light incident surface. And the adhesive layer 24 is attached to the light-emitting surface 224 of the thin plate. The plurality of scattering particles 26 are dispersed on the light exit surface 224 of the thin plate 22 and are fixed to the light exit surface 224 by the adhesive layer 24. The plurality of scattering particles 26 have a distribution of particle size changes. The transparent conductive layer 28 covers the adhesive layer 24 and the plurality of scattering particles 26.

Thereby, when a sunlight illuminates the light incident surface 222 and the plurality of scattering particles 26 dispersed on the light exit surface 224, a distribution of the particle size change corresponds to a broadband range of light passing through the light exit surface 224. The surface of the adhesive layer 24 and the scattering particles 26 is scattered to the transparent conductive layer 28.

In one embodiment, the change in particle size of the plurality of scattering particles is in the range of 0.05 to 20 μm. In practical applications, the variation of the particle size of the plurality of scattering particles 26 may depend on the wavelength bandwidth of the desired scattering.

In a specific embodiment, the first material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). One of the groups. And, the second material may be selected from the group consisting of glass, cerium oxide (SiO ₂ ), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA), and a mixture of the above compounds. One of the groups.

In one embodiment, the transparent conductive layer 28 may be formed of a transparent conductive oxide such as ITO, AZO, BZO, GZO, FTO, and various transparent conductive oxide materials.

In one case, the substrate having broadband light scattering function according to the present invention, wherein the plurality of scattering particles 16 may have a surface of a Lambertian surface or an approximate Lambertian surface.

The Lambertine surface has the following two properties:

1. Regardless of how the surface is illuminated by light, it exhibits the same luminance in all directions of observation, ie the luminance is independent of direction.

2. If all incident light is reflected without any absorption, it is also called a perfect reflecting diffuser.

Further, according to the method of the present invention for producing a substrate having a broadband light scattering function, first, a solution containing a plurality of particles for scattering is formulated. The solution contains from about 0.1 to 10% by weight of SiO ₂ particles, a solvent, a dispersing agent, and a surface treating agent. Next, the particles containing a plurality of scattering particles were uniformly sprayed onto a glass sheet by spray coating using a high-speed disperser. Then, a pre-modulated SiO ₂ gel was sprayed onto the glass sheet. Next, the glass sheet is baked at a temperature (for example, 500 ° C) for a period of time (for example, 3 hours) to form an adhesive layer for fixing the plurality of scattering particles on the glass sheet. Finally, a transparent conductive layer, such as AZO, is formed over the plurality of scattering particles and the glass sheet by a sputtering process. In addition, according to the method of manufacturing a substrate having a broadband light scattering function according to the present invention, after the transparent conductive layer is sputtered, etching is performed on the surface of the transparent conductive layer to increase the roughness of the surface of the transparent conductive layer. The plurality of scattering particles combined with increasing the roughness of the surface of the transparent conductive layer can reduce the reflection of light and simultaneously increase the optical path length of the photon to increase the light absorption to enhance the photocurrent intensity, thereby further improving the photoelectric conversion efficiency.

Table 1 shows the range of variation of the particle size of the plurality of scattering particles 16 in a practical application case. The particle size of the plurality of scattering particles 16 in this case varies approximately from 0.17 μm to 23 μm. As can be seen from Table 1, the main composition is the largest number of particles having a size of 0.5 μm and the particles occupying the largest volume and having a size of 13.5 μm. And since the ratio of the volume of the particles to about 40 μm can be measured, it can be known that the particle size of the plurality of scattering particles can be up to about 40 μm in this case.

Referring to FIG. 3, FIG. 3 is a graph showing the intensity of scattered light transmitted by a substrate having a broadband light scattering function, a commercial glass substrate and a prior art glass substrate in a wide range of wavelengths of light according to the present invention. The sample is a substrate having a broadband light scattering function according to the present invention, wherein the transparent conductive layer of the substrate is an AZO film which is formed by sputtering, and is subjected to an etching process to increase the surface roughness thereof. The sample two is a commercial glass substrate (flat glass), wherein the transparent conductive layer of the substrate is also an AZO film, and is subjected to an etching process to increase the surface roughness thereof. The sample is a conventional glass substrate (Asahi-U). As can be seen from Figure 3, Sample 3, a conventional glass substrate (Asahi-U), has a wavelength range of between 400 nm and 800 nm. Also shown in Figure 3, the third sample, the commercial glass substrate, has a wavelength range that is also approximately between 400 nm and 800 nm. Moreover, the scattered light intensity of the commercial glass substrate in the above wavelength range is slightly larger than the scattered transmitted light intensity of the conventional glass substrate (Asahi-U). As can be seen from FIG. 3, the substrate having the broadband light scattering function according to the present invention, that is, the sample one, can be scattered in a wavelength range of 400 nm to 1200 nm, and can even scatter a wavelength of 1200 nm or higher. And obviously, the scattering light transmission intensity of the substrate having the broadband light scattering function according to the present invention is much greater than the scattering transmitted light intensity of the conventional glass substrate (Asahi-U) and the scattering transmission of the commercial glass substrate (sample 2). brightness.

In summary, the substrate having the broadband light scattering function according to the present invention can effectively improve the efficiency of the tantalum film solar cell. This novel substrate with broadband light scattering function is more effective in improving the efficiency of tandem tantalum film solar cells due to the increased long-wavelength light scattering capability.

The features and spirit of the present invention will be more apparent from the detailed description of the preferred embodiments. On the contrary, the intention is to cover various modifications and equivalents within the scope of the invention as claimed. Therefore, the scope of the patented scope of the invention should be construed as broadly construed in the

1. . . Substrate

12. . . sheet

14. . . Adhesive layer

16. . . Scattering particles

18. . . Transparent conductive layer

122. . . Glossy surface

124. . . Glossy surface

2. . . Substrate

twenty two. . . sheet

twenty four. . . Adhesive layer

26. . . Scattering particles

28. . . Transparent conductive layer

222. . . Glossy surface

224. . . Glossy surface

1A through 1C schematically illustrate a method of fabricating a substrate 1 having a broadband light scattering function in accordance with a preferred embodiment of the present invention.

FIG. 2 is a schematic diagram showing a substrate 2 having a broadband light scattering function according to a preferred embodiment of the present invention.

Figure 3 is a graph showing the intensity of scattered light transmitted over a wide range of wavelengths of a substrate having a broadband light scattering function, a commercial glass substrate, and a prior art glass substrate in accordance with the present invention.

1. . . Substrate

12. . . sheet

14. . . Adhesive layer

16. . . Scattering particles

18. . . Transparent conductive layer

122. . . Glossy surface

124. . . Glossy surface

Claims (10)

A method for manufacturing a substrate having a broadband light scattering function, comprising the steps of: preparing a thin plate formed of a first material, wherein the thin plate has a light incident surface and a light emitting surface opposite to the light incident surface; a plurality of particles for scattering formed by a second material, wherein the plurality of particles for scattering have a distribution of particle size changes; and fixing the plurality of particles for scattering on the light exiting surface of the sheet, wherein the plurality of particles Dispersing particles are dispersed on the light-emitting surface of the thin plate; and a transparent conductive layer is covered on the plurality of scattering particles and the light-emitting surface by a sputtering process; thereby, when a sunlight is irradiated When the surface and the plurality of scattering particles are dispersed on the light-emitting surface, a distribution of the particle size change corresponds to a broadband range of light scattering from the light-emitting surface to the transparent conductive layer. The method of claim 1, wherein the step of fixing the plurality of scattering particles on the light-emitting surface of the sheet is performed by a sol-gel method on the light-emitting surface. An adhesive layer is attached, and the adhesive layer is used to fix the plurality of scattering particles on the light emitting surface. The method of claim 1, wherein the change in the particle size of the plurality of scattering particles is in the range of 0.05 to 20 μm. The method of claim 1, wherein the first material is selected from the group consisting of glass, cerium oxide (SiO ₂ ), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). One of the groups formed. The method of claim 1, wherein the second material is selected from the group consisting of glass, cerium oxide (SiO ₂ ), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate. (PMMA) and one of a group consisting of a mixture of the above compounds. The method of claim 1, wherein the transparent conductive layer is composed of a transparent conductive oxide. A substrate having a broadband light scattering function, comprising: a thin plate formed by a first material, the thin plate having a light incident surface and a light emitting surface opposite to the light incident surface; an adhesive layer, the bonding a layer attached to the light-emitting surface of the thin plate; and a plurality of scattering particles formed by a second material dispersed on the light-emitting surface of the thin plate, wherein the plurality of scattering particles are fixed by the adhesive layer a plurality of scattering particles having a distribution of particle size variations; and a transparent conductive layer covering the bonding layer and the plurality of scattering particles; thereby, when a sunlight is emitted When the light-incident surface and the plurality of scattering particles dispersed on the light-emitting surface are irradiated, light of a wide-band range corresponding to the distribution of the particle size change is scattered from the light-emitting surface to the transparent conductive layer. The substrate of claim 7, wherein the particle size of the plurality of scattering particles is in the range of 0.05 to 20 μm. The substrate of claim 7, wherein the first material is selected from the group consisting of glass, cerium oxide (SiO ₂ ), polymethyl methacrylate (PMMA), and polyethylene terephthalate (PET). One of the group consisting of, and the second material is selected from the group consisting of glass, cerium oxide (SiO ₂ ), polystyrene (PS), polycarbonate (PC), polymethyl methacrylate (PMMA) And one of the group consisting of a mixture of the above compounds. The substrate of claim 7, wherein the transparent conductive layer is formed of a transparent conductive oxide.