TWI574425B - Solar cell and manufacturing method thereof - Google Patents

Description

Solar cell and method of manufacturing same

The invention relates to a solar cell and a preparation method thereof.

In the field of solar cells, in order to enable multiple reflection and multiple utilization of incident light, the light-receiving area is increased, and the chance of light being absorbed is increased. The rough texture design of the solar cell surface is an inevitable step. The solar cell will form a pyramid shape of different sizes on the light incident surface by roughening etching, in order to increase the effective path increase of light, thereby increasing the absorption rate of sunlight. In the roughening etching process, since the etching liquid etches the surface of the germanium wafer (100), thereby exposing the (111) cross section, a pyramidal structure is produced.

However, if the valley formed between the bottoms of each pyramid-shaped structure is too small, the metal impurities remaining in the valley portion are not easily cleaned in the subsequent cleaning process, thereby affecting the open circuit voltage and photoelectric conversion efficiency of the solar cell.

According to various embodiments of the present invention, a sun is provided The energy battery comprises: a semiconductor substrate having a light incident surface, the light incident surface having a plurality of pyramidal structures, wherein each of the pyramidal structures comprises a top end, and any two adjacent pyramidal structures have a valley portion therebetween. The valley portion has a radius of curvature of 25 to 500 nm; an emitter layer is located in the semiconductor substrate and adjacent to the light incident surface; and an electrode is disposed on the semiconductor substrate.

In some embodiments, the solar cell is a Hetero-Junction Solar Cell and the emitter layer is P-doped with boron.

In some embodiments, a reflective layer is further included overlying the emitter layer.

A plurality of embodiments of the present invention provide a method for manufacturing a solar cell. The method includes the steps of: providing a semiconductor substrate having a process surface; and roughening etching on the process surface to form a plurality of pyramid structures, wherein a valley between two adjacent pyramidal structures; oxidizing the surface of the pyramidal structure to form an oxide layer, forming a non-oxidized portion of each valley to form a rounded structure; and removing the oxide layer to smooth the surface The structure is exposed.

In some embodiments, after the oxide layer is removed, a doping process is performed on the process surface to form an emitter layer in the semiconductor substrate and adjacent to the process surface.

In some embodiments, after forming the emitter layer, further comprising forming an anti-reflective layer on the emitter layer.

In certain embodiments, a method of forming the oxide layer includes Use atmospheric constant piezoelectric slurry.

In some embodiments, etching the oxide layer comprises using an etchant, and the etchant comprises HF, HCl, or a combination thereof.

In some embodiments, the atmospheric normal piezoelectric slurry has a power of between 1 and 2.5 kW.

In some embodiments, further comprising forming a plurality of electrode contact emitter layers.

The above and other objects, features, and advantages of the invention will be apparent from

100‧‧‧ solar cells

110‧‧‧Semiconductor substrate

120‧‧‧Top

130‧‧‧谷部

150‧‧‧Oxide layer

132‧‧‧The valley marked by the dotted line

200‧‧‧ solar cells

210‧‧‧Semiconductor substrate

260‧‧ ‧ emitter layer

270‧‧‧Anti-reflective layer

280‧‧‧electrode

1A-1C is a cross-sectional view showing each process stage of a method of fabricating a solar cell according to an embodiment of the present invention.

Fig. 1D is an enlarged schematic view showing the smoothing structure of the valley portion in Fig. 1C.

2 is a schematic cross-sectional view showing a solar cell according to some embodiments of the present invention.

The manufacture and use of this embodiment will be discussed in detail below, However, it should be appreciated that the present invention provides an innovative concept of practice in which a wide variety of specific content can be presented. The embodiments or examples described below are illustrative only and are not intended to limit the scope of the invention.

In addition, in this document, spatially relative terms such as "below", "under", "below" may be used in order to facilitate a description of the relationship between a component or feature and other components or features depicted in the drawings. ", above", "above" and similar terms. These spatially relative terms are intended to cover all the different orientations of the component in use or operation, and are not limited to the orientation depicted in the drawings. The device can be oriented in other ways (rotated 90 degrees or in the other direction), and the spatially relative descriptors used herein can be interpreted accordingly.

Various embodiments relating to a solar cell and a method of fabricating the same are provided below, wherein the structure and properties of the solar cell and the preparation steps or operations of the solar cell are described in detail.

The invention discloses a solar cell. 1A to 1C are schematic cross-sectional views showing respective process stages of a method of fabricating a solar cell according to an embodiment of the present invention. Referring to FIG. 1A, roughening etching is performed on a process surface of the semiconductor substrate 110 to form a rough surface including a plurality of pyramid-shaped structures to reduce loss of reflected light. In one embodiment, the (100) surface of the semiconductor substrate 110 is etched using an alkaline etching solution of potassium hydroxide to expose a (111) cross section, resulting in a plurality of pyramidal structures. The size of these pyramidal structures can be uniform or different (randomly distributed). Each pyramidal structure has a top end 120 and a valley portion 130 between the bottoms of any two pyramidal structures. In still other embodiments, the gold described above The word tower structure can also be a convex structure of other shapes.

The semiconductor substrate 110 may be an N-type or a P-type, and the semiconductor substrate 110 may use a semiconductor such as amorphous silicon, polycrystalline, GaAs, InGaP, or a tri-five semiconductor material. When materials of different semiconductor substrates 110 are used, different etching solutions or etching methods may be used to form rough surfaces including a plurality of pyramidal structures. In some embodiments, the etching process may use an anisotropic etching or an isotropic etching; a chemical acid etching process (an etching solution such as hydrofluoric acid or nitric acid) or a chemical alkaline etching process may be used (the etching liquid is, for example, Potassium hydroxide or isopropanol). It should be understood by those of ordinary skill in the art that these process conditions are for illustrative purposes only, and any suitable process conditions can be used in the context of maintaining the embodiments.

In FIG. 1B, after the rough surface including the plurality of pyramid-shaped structures is completed, the rough surface of the semiconductor substrate 110 is oxidized, and the surface of each pyramid-shaped structure in the rough surface is formed with the oxide layer 150, and the valley portions 130 are not formed. The oxidized portion forms a rounded structure 132. In one embodiment, the surface of the pyramidal structure is oxidized using Atmospheric-pressure Plasma (AP) to form an oxide layer 150. The atmospheric normal piezoelectric pulp has a power of 1 to 2.5 KW, such as 1.2 KW, 1.4 KW, 1.6 KW, 1.8 KW, 2 KW or 2.2 KW, preferably 1.4 to 2.0 KW. Any conventional oxidation process can be used to oxidize the surface of the pyramidal structure to form an oxide layer 150, such as a thermal oxidation process.

In FIG. 1C, the oxide layer 150 formed on the surface of the pyramidal structure is removed to expose the rounded structure 132 of the valley 130. In an embodiment In the wet etching, the etching solution contains HF, HCl or a combination thereof. Dry etching or reactive ion etching (RIE) can also be used. In one embodiment, the etch process is Over Etching to ensure that the oxide layer 150 is completely removed.

FIG. 1D is an enlarged schematic view showing the rounded structure 132 of the above-mentioned trough. The rounded structure 132 of the valley has a radius of curvature (rv) between 25 and 500 nm, such as 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm or 450 nm, preferably 100-350 nm. It should be noted that the rounding structure 132 of each valley 130 has been formed when the oxide layer 150 is formed, and the oxide layer 150 is removed by etching to expose the rounding structure 132.

After rough etching to form a plurality of pyramid-shaped structures, if the valleys 130 between the bottoms of the pyramid-shaped structures are too narrow, metal impurities are likely to remain therein, and are not easily removed in subsequent processes, and residual metal impurities may affect solar energy. The photoelectric conversion efficiency and open circuit voltage (Voc) of the battery, so the radius of curvature of the valley portion 130 smoothing structure 132 cannot be too small. If the radius of curvature of the rounded portion 132 of the valley portion 130 between the bottoms of the pyramid-shaped structure is too large, the photoelectric conversion efficiency is lowered because volume expansion causes generation in the semiconductor substrate 110 when the concave-convex surface topography of the pyramid-shaped structure is oxidized. Larger stresses, if these stresses exceed the critical shear stress on the surface of the semiconductor substrate 110, a misalignment type of defect will result in an increase in carrier composite probability and thus a reduction in the photoelectric conversion efficiency of the solar cell.

Table 1 shows the performance data of a solar cell obtained according to an embodiment of the present invention. The control group is a solar cell with no smoothing structure of the valley portion 130; the experimental group is a solar cell with a rounded structure 132 of the valley portion 130, wherein the method of oxidizing the surface of the pyramidal structure is to use an atmospheric constant piezoelectric slurry, an atmospheric common piezoelectric slurry. The power is 1.6KW. As can be seen from Table 1, the average photoelectric conversion efficiency of the solar cell having the smoothing structure 132 of the valley portion 130 is increased by 0.11%, and the open circuit voltage is increased by 0.003V.

As shown in FIG. 2, after the oxide layer 150 formed on the surface of the pyramid structure is removed, a process of doping the semiconductor substrate 110 may be performed to form an emitter layer 260 in the semiconductor substrate and adjacent to the process surface. . The dopant type used in the doping process is different from the conductivity type of the semiconductor substrate 110. In one embodiment, the semiconductor substrate 110 is P-type and is doped to an N-type, such as a single crystal germanium solar cell or a polycrystalline germanium solar cell, a semiconductor. The substrate 110 is of a P type, and the dopant may be an N type of phosphorus. In another embodiment, the semiconductor substrate 110 is N-type and is P-type, such as a Heterojunction Solar Cell, the semiconductor substrate 110 is N-type, and the dopant may be P-type boron. The emitter layer 260 can be any conventional emitter, such as a selective emitter.

In an embodiment, after the emitter layer 260 is formed, an anti-reflection layer 270 may be formed on the emitter layer 260 to increase the light absorption of the solar cell, thereby improving the conversion efficiency of the solar cell. The type of the antireflection layer may be, for example, a single-layer antireflection film, a multilayer antireflection film, a subwavelength structure antireflection layer, or a nanostructure antireflection layer. Anti-reflective layer 270 can use plasma-assisted chemical gas Plasm Enhanced Chemical Vapor Deposition (PECVD) or other conventional means is deposited on the emitter layer 260.

In one embodiment, a plurality of electrodes 280 may be formed to contact the emitter layer 260 after forming the anti-reflective layer 270. The electrode 280 may be any conventional electrode, such as a finger electrode. In one embodiment, a metal paste is applied to the wafer using a screen printer and then fired at a high temperature to form an electrode.

An advantage of an embodiment of the present invention is that a valley between the bottoms of the pyramid-shaped structure has a rounded structure of solar cells, which can reduce metal impurity residues to improve photoelectric conversion efficiency and open circuit voltage.

The various embodiments are summarized above to enable those skilled in the art to understand the various aspects of the disclosure. Those skilled in the art will understand and be able to use this basis to design or modify other compositions and structures for the same purpose and/or embodiments having the same advantages as described herein. Those skilled in the art will appreciate that any substitution, substitution, or alteration can be made without departing from the spirit and scope of the invention.

200‧‧‧ solar cells

210‧‧‧Semiconductor substrate

260‧‧ ‧ emitter layer

270‧‧‧Anti-reflective layer

280‧‧‧electrode

Claims (6)

A method of manufacturing a solar cell, comprising: providing a semiconductor substrate having a process surface; roughening etching on the process surface to form a plurality of raised structures, wherein any two adjacent ones of the raised structures Having a valley portion; oxidizing the surfaces of the raised structures using an Atmospheric-pressure Plasma process to form an oxide layer such that portions of the valleys that are not oxidized form a rounded structure; Removing the oxide layer exposes the rounded structure. The method for manufacturing a solar cell according to claim 1, after removing the oxide layer, further comprising performing a doping process on the process surface to form an emitter layer in the semiconductor substrate and adjacent to the process surface. The method of manufacturing a solar cell according to claim 2, further comprising forming an anti-reflection layer on the emitter layer. A method of fabricating a solar cell according to claim 1, wherein etching the oxide layer comprises using an etchant, and the etchant comprises HF, HCl or a combination thereof. The method of manufacturing a solar cell according to claim 1, wherein the atmospheric constant piezoelectric slurry has a power of 1 to 2.5 kW. The method of manufacturing a solar cell according to claim 3, further comprising forming a plurality of electrodes to contact the emitter layer.