CN105355697B - A kind of thin-film solar cells of light trapping structure and its preparation method and application structure - Google Patents

Abstract

The present invention relates to the thin-film solar cells of a kind of light trapping structure and its preparation method and application structure, the light trapping structure includes two-dimentional right angle pyramid shape and falls into light silicon layer (4), the two-dimentional right angle pyramid shape falls into light silicon layer (4) and is made up of the two-dimentional right angle rectangular pyramid array of micro-nano periodicity and Non-completety symmetry, and the shape of the wherein two-dimentional right angle rectangular pyramid of signal period is：Bottom surface is square, and a seamed edge is each perpendicular to bottom surface perpendicular to bottom surface, adjacent with the seamed edge two sides, and two sides favour the bottom surface in addition.Light trapping structure disclosed by the invention is that have stronger coupled characteristic, possesses the characteristics of wide spectrum influx and translocation, angle sensitivity are good, and influx and translocation effect is more isostructural than traditional inverted pyramid better.

Description

A light-trapping structure, its manufacturing method, and thin-film solar energy using the structure Battery

technical field

The invention relates to a light-trapping structure, a manufacturing method thereof and a thin-film solar cell using the structure.

Background technique

In recent years, with the progress of science and technology and the development of economy, the demand for energy in various countries is increasing, and non-renewable energy sources such as electricity, coal, and oil are frequently in urgent need, which promotes the rapid development of the photovoltaic industry. The core device of solar photovoltaic power generation is solar cells. Silicon solar cells occupy a dominant position in solar cells due to their wide range of sources and low cost. At present, solar cells mainly include crystalline silicon solar cells and thin film solar cells. Compared with crystalline silicon solar cells, thin-film solar cells have the advantages of low cost, large-area production, and better low-light performance. However, since the thickness of the absorbing layer is reduced in thin-film solar cells, the absorption length is correspondingly reduced, resulting in low photoelectric conversion efficiency of thin-film silicon solar cells. A large number of studies have shown that the preparation of a periodic and regular nanostructure of a specific shape on the surface of a silicon wafer can not only increase the effective movement length of sunlight inside the silicon wafer, cause the coupling between incident light, but also reduce the incident light from The refractive index in the propagation path from air to silicon wafer effectively improves the conversion efficiency of solar cells.

At present, in order to improve the efficiency of silicon-based thin-film solar cells in industrial production, the main method is to adopt surface disordered structure and pyramid structure. The first is to use surface disordered dielectric textures or metal particles as forward or backward scatterers. For example, Rahul Dewan studied the light-trapping ability of surface disordered light-trapping structures. He first used an atomic force microscope (AFM) to scan the shape of the disordered structure on the surface. In order to show the structure of the surface more clearly, he listed the curves with three times the amplitude and three times the amplitude. On the basis of obtaining the shape of the curve, he further calculated the light-trapping ability of the structure with the rigorous coupled wave algorithm (RCWA). Although the absorption capacity of thin film batteries can be improved with this structure, it can be seen from the results of this study. For the disordered structure, the surface structure is made first and then the parameter analysis is performed. Therefore, there is a certain degree of contingency in the design and research of surface disordered light-trapping structures, and it is impossible to repeat some better structural surface types, let alone make improvements based on specific surface types. The second is to use periodic dielectric structures or photonic crystals to capture light, and the use of grating coupling can effectively improve photon absorption in a certain bandwidth. For example, Gang Chen et al. used wet etching to prepare an inverted pyramid structure in a silicon-based solar cell with a thickness of 5 μm, and achieved a short-circuit current density of 37.1mA/cm2. However, the preparation method of wet etching often also forms disordered structures. Although random and disordered light-trapping structures can obtain absorption growth in a wide spectral range, it is difficult to maximize the enhanced absorption due to the disordered arrangement of the structures. In order to arrange the nanostructures in an orderly manner, they used a combination of mask photolithography and wet etching, but this method is only applicable to single crystal silicon solar cells.

Generally speaking, the prior art using disordered structures or pyramids can only increase the range of spectral absorption limited, the absorption efficiency is not high, the manufacturing process is complicated, and the cost is also high.

Contents of the invention

The object of the present invention is to provide a light-trapping structure and its manufacturing method and a thin-film solar cell using the structure, which not only has periodic surface coupling to enhance broad-spectrum absorption efficiency, enhance spectral absorption, and make no mask plate , Simple, fast and large forming area.

In order to solve the above-mentioned technical problems, the present invention adopts the following technical solutions:

A light-trapping structure, comprising a two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer, the two-dimensional right-angled quadrangular-pyramid-shaped light-trapping silicon layer is composed of a micro-nano periodic and non-completely symmetrical two-dimensional right-angled quadrangular pyramid array, wherein a single The shape of the periodical two-dimensional right-angled quadrangular pyramid is: the bottom surface is square, one edge is perpendicular to the bottom surface, the two sides adjacent to the edge are both perpendicular to the bottom surface, and the other two sides are inclined to the bottom surface.

Furthermore, the thickness of the silicon absorbing layer is 1000 nm, the period of the two-dimensional rectangular pyramid varies from 300 nm to 1300 nm, and the height varies from 100 nm to 1000 nm.

Furthermore, the period of a single period of the two-dimensional rectangular pyramid is 700nm, and the height is 900nm.

A method for preparing a light-trapping structure, comprising the following steps: using double-beam interference to engrave a rectangular pyramid-shaped light-trapping structure on silicon, the formation method of a single period of two-dimensional rectangular pyramid is: two beams with the same light intensity Interfering light, when two beams of coherent light arrive at the inclined substrate surface with a certain inclination angle, the optical path of the two beams of interfering light is about an integer multiple of the wavelength, so that the originally symmetrical cosine interference pattern is cut off in half and becomes incomplete The symmetrical structure is then exposed for the second time by rotating the substrate by 90°, and the exposed positive photoresist is developed to form the two-dimensional right-angled quadrangular pyramid structure.

A thin-film solar cell, comprising a metal electrode, the outer layer of the metal electrode is sequentially provided with a first transparent conductive oxide thin film layer, a silicon absorption layer, a two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer and a second transparent conductive oxide The thin film layer, wherein the two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer is composed of a micro-nano periodic and non-completely symmetrical two-dimensional right-angled quadrangular pyramid array, wherein the shape of a single period of two-dimensional right-angled quadrangular pyramid is: the bottom surface is a square , one edge is perpendicular to the bottom surface, two side surfaces adjacent to the edge are perpendicular to the bottom surface, and the other two sides are inclined to the bottom surface.

Compared with the prior art, the beneficial effects of the present invention are: the light-trapping structure disclosed in the present invention is an ordered periodic non-completely symmetrical two-dimensional structure, has strong coupling characteristics, has enhanced broad-spectrum absorption, and angle sensitivity Good characteristics, the absorption enhancement effect is better than that of the traditional inverted pyramid and other structures, and can be directly prepared by a simple two-beam interference lithography method. The forming area is large, not limited by the material of the absorbing layer, and no mask is required, which can be simple and fast made.

Description of drawings

FIG. 1 is a three-dimensional schematic diagram of a single-period two-dimensional right-angled quadrangular pyramid of a light-trapping structure in a battery according to the present invention.

Fig. 2 is a short-circuit current density of different periods and heights of a light-trapping structure of the present invention.

Fig. 3 is the absorption spectrum of a light-trapping structure of the present invention when the cell is at normal incidence.

FIG. 4 is an absorption spectrum of a light trapping structure according to the present invention as it varies with angle.

FIG. 5 is a schematic diagram of a semi-finished product structure of a one-dimensional right-angled quadrangular pyramid structure produced by double-beam interference lithography in the invention of a method for preparing a light-trapping structure.

FIG. 6 is a schematic diagram of a finished structure of a two-dimensional right-angled quadrangular pyramid structure fabricated by double-beam interference lithography in the invention of a method for preparing a light-trapping structure.

Fig. 7 is a schematic cross-sectional view of a thin film solar cell of the present invention.

In the figure: 1-metal electrode, 2-the first transparent conductive oxide film layer, 3-silicon absorbing layer, 4-two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer, 5-the second transparent conductive oxide film layer.

detailed description

In order to make the object, technical solution and advantages of the present invention clearer, the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described here are only used to explain the present invention, not to limit the present invention.

Fig. 1 shows an embodiment of a light-trapping structure of the present invention: a light-trapping structure comprising a two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer 4, and the two-dimensional right-angled square-pyramid-shaped light-trapping silicon layer 4 is made of The micro-nano periodic and non-completely symmetrical two-dimensional right-angled rectangular pyramid array is composed of a single periodic two-dimensional right-angled rectangular pyramid. The side surfaces are both perpendicular to the bottom surface, and the other two sides are inclined to the bottom surface.

The absorption effect of the two-dimensional rectangular pyramidal light-trapping layer can be reflected in the following way: The absorption enhancement effect of the periodic two-dimensional rectangular pyramidal light-trapping structure can be evaluated according to the short-circuit current density J _sc at normal incidence, the expression as follows:

Among them, q is the amount of charge, λ is the wavelength of incident light, h is Planck’s constant, c is the speed of light, I _AM1.5G (λ) is the AM1.5G solar spectral radiation, A (λ) is the absorption spectrum of the battery, which is related to The photonic structure is closely related, and the absorption spectrum A(λ) of the battery will be expanded in the solar spectrum from 300nm to 1100nm during calculation.

According to a preferred embodiment of a light trapping structure of the present invention, the thickness of the silicon absorption layer 3 is 1000nm, the period (width) P of a single period of the two-dimensional rectangular pyramid varies from 300nm to 1300nm, and the height H The variation range is from 100nm to 1000nm.

Figure 2 shows a preferred embodiment of a light-trapping structure of the present invention. The period P of a single period of a two-dimensional rectangular pyramid is 700nm, the height H is 900nm, and the corresponding short-circuit current density is 31.01mA/cm ² . Similarly, an optimal inverted pyramid light-trapping structure can also be obtained through this optimization method, with a period of 600nm, a height of 700nm, and a short-circuit current density of 28.27mA/cm ² .

In order to reflect the effect of this optimal light-trapping structure on the absorption enhancement of the cell, it is compared with the cell with the traditional pyramid light-trapping structure, the flat cell without the light-trapping structure, and the theoretical absorption limit. As shown in Figure 3, cells with light-trapping structures clearly absorb better than flat-panel cells over the entire solar spectrum, and both approach the limit. At the same time, the best rectangular pyramid light-trapping structure has a significantly better absorption enhancement effect on the battery in the long-wavelength band above 700nm than the best inverted pyramid light-trapping structure.

Fig. 4 has shown the angle spectrum analysis embodiment of a kind of light-trapping structure of the present invention, when the incident angle changes from 0 ° to 85 °, the absorption spectrum of the best right-angled quadrangular pyramid-shaped light-trapping structure also shows that this right-angled quadrangular pyramid-shaped The light-trapping structure is not sensitive to angle, similar to an inverted pyramid. Considering the preparation process of the light-trapping structure, the rectangular pyramid-shaped light-trapping structure can be prepared by simple two-beam interference, and the forming area is large. Therefore, such a periodic two-dimensional rectangular pyramid-shaped light-trapping structure is more practical.

Fig. 5 and Fig. 6 also show a kind of method for preparing the light-trapping structure of the present invention, comprise the following steps: engrave and make right-angled quadrangular-pyramid-shaped light-trapping structure on silicon with double-beam interference, the two-dimensional right-angled quadrangular-pyramid of single period The formation method is: two beams of interference light with the same light intensity, when the two beams of coherent light reach the inclined substrate surface with a certain inclination angle, the optical path of the two beams of interference light is about an integer multiple of the wavelength, so that the original symmetrical The cosine interference pattern is cut in half to become an asymmetric structure, and then exposed for the second time by rotating the substrate by 90°, and the exposed positive photoresist is developed to form the two-dimensional right-angled quadrangular pyramid structure.

Fig. 7 shows an embodiment of a kind of thin film solar cell of the present invention, combined with Fig. 1 can know: a kind of thin film solar cell, comprises metal electrode 1, is characterized in that: the outer layer of described metal electrode 1 is provided with first Transparent conductive oxide thin film layer 2, silicon absorbing layer 3, two-dimensional right-angled quadrangular pyramid-shaped light-trapping silicon layer 4 and a second transparent conductive oxide thin-film layer 5, wherein the two-dimensional right-angled rectangular pyramid-shaped light-trapping silicon layer 4 is composed of The micro-nano periodic and non-completely symmetrical two-dimensional right-angled rectangular pyramid array is composed of a single periodic two-dimensional right-angled rectangular pyramid. The side surfaces are both perpendicular to the bottom surface, and the other two sides are inclined to the bottom surface.

Although the invention has been described herein with reference to a number of illustrative embodiments thereof, it is to be understood that numerous other modifications and implementations can be devised by those skilled in the art which will fall within the scope of the disclosure disclosed herein. within the scope and spirit of the principles. More specifically, within the scope of the disclosure, drawings and claims of the present application, various modifications and improvements can be made to the components and/or layout of the subject combination layout. In addition to variations and modifications to the component parts and/or layout, other uses will be apparent to those skilled in the art.

Claims (1)

1. A kind of 1. method for preparing light trapping structure, it is characterised in that comprise the following steps：Work is scribed on silicon with two-beam interference Right angle pyramid shape light trapping structure, the generation type of the two-dimentional right angle rectangular pyramid of signal period are：Two beams have same light intensity Interference light, when two beam coherent lights, which reach, to be had on the tilted substrates face at certain angle of inclination, the light path of the two beam interferometers light is The integral multiple of wavelength so that the cosine interference pattern of otherwise symmetrical reams half, becomes unsymmetric structure, then by rotating base 90 ° of plate, second of exposure, the positive photoresist that is exposed is developed to form the two-dimentional right angle rectangular pyramid structure, the list later The shape of the two-dimentional right angle rectangular pyramid in individual cycle is：Bottom surface is square, and a seamed edge is adjacent with the seamed edge perpendicular to bottom surface Two sides are each perpendicular to bottom surface, and two sides favour the bottom surface in addition.