TWI398012B - Surface texturization of solar cell by using multiple-laser beams ablation and solar cell with surface texturization - Google Patents

Description

Multi-laser beam surface roughening method for solar cells and solar cell with roughened surface

The invention relates to a surface roughening method, in particular to a multi-laser beam surface roughening method for solar cells and an application thereof.

Although Photovoltaic (PV) is not absent in the development of energy conservation and environmental protection and promoting the popularization of renewable energy, it is always unable to occupy a leading role. The main reason is that the current cost of solar photovoltaic power generation is still high but the performance of energy conversion efficiency is not good. Therefore, how to effectively increase solar energy efficiency is an important topic for most people at present.

At present, the cost of the solar panel is relatively low, and the average reflectance of visible light is as high as 37%. In other words, only 63% of the incident sunlight can be used as a photoelectric conversion by the solar panel. At present, silicon nitride (Si ₃ N ₄ ) is used as an anti-reflection layer, and the conversion efficiency is about 17%. Although it is slightly better than a solar panel without an anti-reflective coating, it is still slightly insufficient. In order to improve the efficiency of light-to-electricity, the most effective technique is to use surface roughening or the application of an anti-reflective layer to increase the surface area of the enamel wafer and the number of incident light reflections.

At present, the development of surface roughening of solar cells is dominated by microstructure pyramids. Among them, a buried electrode solar cell in a BCSC (buried contact solar cell) has a roughened structure of a pyramid formed by an etching liquid on the surface thereof, and a roughened structure is also processed in the back electrode portion, and such a two-layer roughened structure is used. It can increase the residence time of light in the absorption layer, and the overall conversion efficiency can reach 21~22%. The surface roughening technology is applied to a solar cell, which can effectively reduce the reflectance, increase the time that the light stays inside, increase the absorption rate of light, and thereby increase the photoelectric conversion efficiency of the solar cell.

It is found in various surface roughening techniques that the greater the aspect ratio of the roughened structure, the higher the anti-reflection efficiency. Therefore, the roughening technique has the best periodic nanostructure and the irregular nano-roughening structure. The irregular coarsening of the micron and nano-scale mixing and the anti-reflection film are inefficient. However, in order to obtain the nano periodic structure, the colloidal crystal self-assembled nanomaterial is currently used as a mask, and the etching effect is best, but this method requires more steps, and the cycle can only control the nanosphere. The change in the diameter makes it relatively impossible to produce a roughened surface having a complicated shape, and it is impossible to achieve a good surface roughening effect.

In order to solve the complicated production process of the existing nano-roughened structure and the coarsening result is not limited by the process technology, the complex roughening effect cannot be performed, and the interference pattern generated by the multi-channel laser beam forms a periodic thick surface on the surface of the solar cell. The surface can be changed, and the interference pattern can be changed very much to achieve the purpose of forming a complicated rough surface.

In order to solve the foregoing technical problems, the present invention provides a method for roughening a plurality of laser beam surfaces for a solar cell, the steps comprising: generating a plurality of laser beams: generating a plurality of laser beams by laser passing through the beam splitting element; The ray light strikes the laser light at a point: the laser light is focused on a point by a confocal system, and each laser light generates an interference phenomenon at the point to form an interference laser light; and the roughening solar cell is processed by the interference laser light. Surface: a surface having a periodic roughening surface formed by the interference laser light on the surface of one of the photoelectric conversion layers of a solar cell.

Wherein, the multi-channel laser light is generated by using a laser to generate a laser output light, and the laser output light is divided into a plurality of laser light by an optical diffraction element.

The invention further provides a solar cell with a roughened surface, comprising: a back surface conductive layer, a photoelectric conversion layer and a front conductive layer laminated in sequence, wherein the photoelectric conversion layer is roughened by a multi-laser beam surface The photoelectric conversion layer forms a roughened surface, and the step of the multi-laser beam surface roughening method comprises: generating a plurality of laser beams: generating a plurality of laser beams by laser passing through the beam splitting element; and focusing the multi-channel laser light to interfere at a point Laser light: each laser light is focused on a point through a confocal system, and each laser beam generates interference at the point to form an interference laser light; and the surface of the solar cell is roughened by interference laser light processing: The light is photoetched on the surface of the photoelectric conversion layer to form a surface having a periodic roughening.

The material of the photoelectric conversion layer is a photoelectric conversion layered element formed of a germanium semiconductor, a tri-five semiconductor, or a polymer.

The structural composition of the photoelectric conversion layer may be a photoelectric conversion structure of a pn type or a pin type.

Wherein, the surface of the front conductive layer is plated to form an anti-reflection layer.

Thereby, the present invention can form a rough, highly complex surface on the solar cell, and the process is simple, and therefore, it is very suitable for surface roughening of various solar cells.

Please refer to the first figure, which is a side view layer structure diagram of an embodiment of a solar cell (10) having a roughened surface according to the present invention, which comprises sequentially laminating a back surface conductive layer (11) and a photoelectric conversion layer. (12) a front conductive layer (14) and an encapsulation layer (15). In use, incident light is incident from a side of the encapsulation layer (15), and the incident light generates electrons in the photoelectric conversion layer (12). The pair of holes, and in turn, generates power output to a load via the backlight conductive layer (11) and the front conductive layer (14).

The material, structure and type of the photoelectric conversion layer (12) are not limited. For example, the photoelectric conversion layer (12) may be a germanium semiconductor, a tri-five (such as gallium arsenide) semiconductor, or a polymer (such as dye sensitization). The photoelectric conversion layered element formed by the solar cell; the structural composition of the photoelectric conversion layer (12) may be a pn-type or pin-type photoelectric conversion structure. The photoelectric conversion layer (12) made of a semiconductor can be further subdivided by the crystallization characteristics of the material, and the semiconductor can be exemplified as a single crystallized silicon, a poly-crystallized silicon, and Amorphous silicon. When the photoelectric conversion layer (12) differs depending on the selected material, structure and material crystal state, the process and steps are slightly different. Taking the photoelectric conversion layer (12) made of amorphous germanium as an example, the amorphous germanium can be plated on any substrate by means of vaper deposition, and the substrate can be a metal foil substrate or a transparent plastic. Before plating the photoelectric conversion layer (12) made of amorphous germanium on a substrate, a glass substrate, a semiconductor substrate, etc., the back surface conductive layer (11) needs to be plated first, and an electrode pattern is formed according to design requirements, and then The photoelectric conversion layer (12) and the front conductive layer (14) are sequentially plated.

In order to reduce the solar light reflection of the photoelectric conversion layer (12) and thereby improve the energy conversion efficiency, the present embodiment applies a multi-laser beam surface roughening method (50) to the incident surface of the photoelectric conversion layer (12). The conversion layer (12) forms a roughened surface.

Referring to the second and third figures, the step of the multi-laser beam surface roughening method (50) comprises: generating multiple laser light (51): using a laser (or femtosecond laser) as a laser The light source produces a laser output light (60) that is split into a plurality of laser beams (62) by an optical diffracting element (71).

Focusing multiple laser light at a point to produce interference laser light (53): focusing multiple laser light (62) through a confocal system (73) (eg, a confocal optical lens system) to focus the laser light (62) separately At one point, each of the laser light (62) causes an interference phenomenon at this point to form an interference laser light (65). Interference is a characteristic that the amplitude of a wave can be superposition. When two or more beams are spatially superimposed, the amplitude of the wave changes with distance or time, and a stable intensity appears in the superimposed region. distributed. The confocal system (73) used in this embodiment includes a first lens (L1) and a second lens (L2) of the common optical axis, by changing the first and second lenses of the confocal system (73) ( The focal length of L1, L2) can control the period (p) and hole diameter (d) of the interference fringes of the interference laser light (65). If the interference laser light (65) is projected onto a plane, the period (p) is p = λ / 2 sin θ, and the hole diameter (d) is d = λ / 4 sin θ, where λ is the wavelength of the laser light (62), and θ is the Ray The phase of the light (62).

In addition, the above-mentioned laser surface etching using a laser utilizes the multiphoton absorption property of the material to cause etching and erosion of the material, so that it can be processed on the surface of many different materials. In this embodiment, the periodic microstructured surface can be effectively fabricated by laser matching with the aforementioned multi-beam interference technique. According to the calculation result, the laser output light (60) is interfered by optical diffraction, and the local energy intensity in the formation of periodic constructive interference is increased, and the laser light of different numbers (62) is utilized. By adjusting the phase of each of the laser light (62), it is advantageous to etch the roughened surface microstructure due to the increase in strength.

Further, by adjusting the phase relationship of the laser light (62), the interference pattern and the intensity distribution of the interference laser light (65) formed may be different, and therefore, in addition to the foregoing, the number of laser light (62) can be determined. The adjustment of the position layout changes the interference pattern of the interference laser light (65), and the phase difference of each laser light (62) can be selected to adjust the light shape (interference pattern) of the interference laser light (65). effect.

The surface of the solar cell is roughened by interference laser light processing (55): photolithography is performed on the surface of the internal structure of the solar cell (10) having the roughened surface by the interference laser light (65), so that the roughened surface is The light incident surface of the solar cell (10) is roughened. By way of example, the interference conversion light (65) allows the photoelectric conversion layer (12) to form a roughened and periodic surface structure, thereby achieving the technical effect of reducing the surface reflectivity of the photoelectric conversion layer (12). Taking the photoelectric conversion layer (12) made of amorphous germanium as an example, the structure of the photoelectric conversion layer (12) is assumed to be a pn-type photoelectric conversion element including a p-type semiconductor layer and an n-type semiconductor layer. In order to form a roughened surface structure having a periodic, nano-scale on the photoelectric conversion layer (12), after the p-type semiconductor layer is plated, the multi-laser beam surface roughening method (50) is used for photolithography. The p-type semiconductor layer is changed to form a surface structure pattern, and then the n-type semiconductor is plated on the surface after the p-type semiconductor layer is roughened, and finally the front conductive layer (14) is plated. The multi-laser beam surface roughening method (50) allows the photoelectric conversion layer (12) to form a surface roughened structure.

Further, in order to further reduce the surface reflectance of the solar cell (10) having the roughened surface, after the front conductive layer (14) is plated, an anti-reflection layer may be further plated to form the anti-reflection layer. The method of fabrication can be accomplished by physical or chemical vapor deposition.

Further, in order to enhance the stability of the solar cell (10) having the roughened surface, a water-resistant and anti-oxidation coating may be further plated on the anti-reflection layer.

Please refer to the fourth figure, which is the photoelectric conversion layer (12) of the present embodiment, wherein the multi-laser beam surface roughening method (50) generates interference laser light through different numbers of laser light (62) ( 65) The result of measuring the light reflectance after surface roughening, it can be seen from the figure that the process method proposed in the embodiment can significantly improve the anti-reflection effect of the light incident surface of the solar cell (10) having the roughened surface. .

(10)‧‧‧ solar cells

(11)‧‧‧ Back conductive layer

(12) ‧‧‧ photoelectric conversion layer

(14) ‧‧‧ front conductive layer

(15)‧‧‧Encapsulation layer

(50) ‧‧‧ Surface roughening method

(51) ‧‧‧Multiple laser light

(53) ‧ ‧ Focus on multiple lasers at a point to produce interference laser light

(55) ‧‧‧Making the surface of roughened solar cells by interference laser light processing

(60)‧‧‧Laser output light

(62)‧‧‧Laser light

(65) ‧ ‧ Interfering with laser light

(71)‧‧‧Optical diffractive components

(73)‧‧‧Confocal system

(L1)‧‧‧First lens

(L2)‧‧‧second lens

The first figure is a layered schematic view of an embodiment of a solar cell with a roughened surface of the present invention.

The second figure is a flow chart of the method for roughening the surface of a plurality of laser beams according to the present invention.

The third figure is a schematic diagram of the optical path design of the method for roughening the surface of a plurality of laser beams according to the present invention.

The fourth figure is a graph showing the results of light reflection measurement of the solar cell with a roughened surface of the present invention.

annex:

Figures 1 to 7 are reference diagrams showing the intensity distribution of the multiple laser light interference patterns of the present invention.

(50). . . Surface roughening method

(51). . . Produce multiple lasers

(53). . . Focusing on multiple lasers at a point to produce interference with laser light

(55). . . Roughening solar cell surface by interference laser processing

Claims (9)

A method for roughening a surface of a plurality of laser beams for a solar cell, the method comprising: generating a plurality of laser beams: generating a plurality of laser beams by laser passing through the beam splitting element; and focusing the plurality of laser beams at a point to generate interference laser light: Radiating light is focused on a point by a confocal system, each laser beam generates an interference phenomenon at the point to form an interference laser light; and the surface of the solar cell is roughened by interference laser light processing: the interference laser light is used The surface of the photoelectric conversion layer of one of the solar cells is formed to have a periodic roughened surface. The method for roughening a plurality of laser beam surfaces for a solar cell according to claim 1, wherein the generating the multi-channel laser light system uses a laser to generate a laser output light, and then passing the laser output light through a The optical diffractive element divides the laser into laser light of a plurality of tracks. The method of roughening the surface of a plurality of laser beams for a solar cell as described in claim 1 or 2, wherein the phases of the respective laser lights are the same. The method for roughening a plurality of laser beam surfaces for a solar cell according to claim 1 or 2, wherein at least one of the phases of the laser light is different from the phase of the other laser light. A solar cell having a roughened surface, comprising: a back surface conductive layer, a photoelectric conversion layer and a front conductive layer laminated in sequence, wherein the photoelectric conversion layer is roughened by a multi-laser beam surface on the photoelectric conversion layer Forming a roughened surface, the step of roughening the surface of the multiple laser beam comprises: generating a plurality of laser light: generating a plurality of laser light by laser; and focusing the multi-channel laser light to generate interference laser light at a point: causing each of the laser light Focusing on a point through a confocal system, each laser beam produces an interference phenomenon at the point to form an interference laser light; and roughening the surface of the solar cell by interference laser light: the interference laser light is photoetched to the photoelectric The surface of the conversion layer is formed to have a periodic roughened surface. The solar cell having a roughened surface according to claim 5, wherein the material of the photoelectric conversion layer is a photoelectric conversion layered element formed of a germanium semiconductor, a tri-five semiconductor, or a polymer. The solar cell having a roughened surface as described in claim 5 or 6, wherein the photoelectric conversion layer may have a pn-type or pin-type photoelectric conversion structure. The surface of the front conductive layer is plated to form an anti-reflective layer, as in the solar cell having a roughened surface as described in claim 7. The solar cell having a roughened surface as described in claim 8 is further coated with a water-resistant and anti-oxidation coating on the surface of the anti-reflective layer.