JP2017208520A - Solar cell and manufacturing method of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a solar cell.SOLUTION: The solar cell includes: a semiconductor substrate; a light incident surface having a plurality of pyramid structures each including a tip and having valleys having a radius of curvature of 25 to 500 nm between arbitrary adjacent pyramid structures; an emitter layer located in the semiconductor substrate in proximity to the light incident surface; and an electrode located on the semiconductor substrate.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a solar cell and a manufacturing method thereof.

  In order to achieve multiple reflection and multiple use for incident light in the solar cell field, increase the light receiving area, and increase the chance that light rays are absorbed, the texture structure design of the solar cell surface has already been It became an indispensable process. The purpose of forming pyramid shapes of different sizes on the light incident surface by roughening etching in a solar cell is to increase the effective light path of light and further increase the absorption rate of sunlight. During the roughening etching, the etching solution etches the surface of the silicon wafer (100), and further exposes the cross section of (111) to generate a pyramid structure.

  However, if the valleys formed between the bottoms of each pyramid structure are too small, it is difficult to clean the metal impurities remaining in the valleys in a subsequent cleaning process, and further affects the open circuit voltage and photoelectric conversion efficiency of the solar cell. Effect.

  According to a plurality of embodiments of the present invention, a light incident surface having a plurality of pyramid structures each including a tip is provided, and a valley portion having a curvature radius of 25 to 500 nm is provided between any adjacent pyramid structures. Provided is a solar cell comprising a semiconductor substrate, an emitter layer located in the semiconductor substrate close to the light incident surface, and an electrode located on the semiconductor substrate.

  In some embodiments, the solar cell is a hetero-junction solar cell and the emitter layer is a P-type doping of boron.

  In some embodiments, the light emitting device further includes a reflective layer covering the emitter layer.

  Embodiments of the present invention provide a semiconductor substrate having a process surface, and roughening the process surface to form a plurality of pyramid structures, between any adjacent plurality of pyramid structures. A step having valleys, a step of oxidizing the surface of the pyramid structure so as to form an oxide layer, forming a round structure in each non-oxidized portion of the valley, and a step of removing the oxide layer to expose the round structure And providing a method for manufacturing a solar cell.

  In certain embodiments, after removing the oxide layer, the method further includes performing a doping process on the process surface such that an emitter layer is formed in the semiconductor substrate proximate the process surface.

  In some embodiments, the method further includes forming an antireflection layer on the emitter layer after forming the emitter layer.

  In certain embodiments, the method of forming the oxide layer includes using atmospheric pressure plasma.

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

  In certain embodiments, the power of the atmospheric pressure plasma is between 1 and 2.5 KW.

  In certain embodiments, the method further includes forming a plurality of electrodes in contact with the emitter layer.

  To make the above and other objects, features and advantages of the present invention more comprehensible, a particularly preferred embodiment will be illustrated below and described in detail below with reference to the accompanying drawings.

It is a cross-sectional schematic diagram which shows each process step of the manufacturing method of the solar cell by one Embodiment of this invention. It is a cross-sectional schematic diagram which shows each process step of the manufacturing method of the solar cell by one Embodiment of this invention. It is a cross-sectional schematic diagram which shows each process step of the manufacturing method of the solar cell by one Embodiment of this invention. It is an enlarged schematic diagram which shows the round structure of the trough part in FIG. 1C. It is a cross-sectional schematic diagram which shows the solar cell by one embodiment of this invention.

  In the following, the manufacture and use of this example will be discussed in detail, but it should be understood that the present invention provides a practical innovation concept and can be expressed in a wide variety of specific contexts. The embodiments or examples described below are for illustrative purposes only and cannot limit the scope of the present invention.

  In the text, in order to facilitate the explanation of the relationship between an element or feature shown in the drawing and another element or feature, spatial relative terms such as “... below”, “... below”, “more Low, “… above”, “higher” and similar terms may be used. These spatially relative terms include all different orientations during use or operation of the element and are not limited to the orientation shown in the drawings. The device may be oriented in other manners (rotated 90 degrees or positioned in other orientations) and thus may relatively understand the spatial relative terms used herein.

  Below, the Example regarding various solar cells and its manufacturing method is provided, and the structure and property of this solar cell, and the manufacturing process or operation of this solar cell are demonstrated in detail.

  The present invention discloses a solar cell. 1A to 1C are schematic cross-sectional views showing respective process steps of a method for manufacturing a solar cell according to an embodiment of the present invention. See FIG. 1A. In order to reduce the loss of reflected light, a rough surface including a plurality of pyramid structures is formed by rough etching on the process surface of the semiconductor substrate 110. In one embodiment, the (100) surface of the semiconductor substrate 110 is etched with an alkaline etchant solution of potassium hydroxide to further expose the (111) cross section to produce a plurality of pyramid structures. The sizes of these pyramid structures may be uniform or different (random distribution). Each pyramid structure has a tip 120 and a trough 130 between the bottoms of any two pyramid structures. In certain other embodiments, the pyramid structure described above may be other forms of protrusion structures.

  The semiconductor substrate 110 may be N-type or P-type, and a semiconductor such as amorphous silicon, polysilicon, GaAs, InGaP, or a III-V group semiconductor material can be used. If different semiconductor substrate 110 materials are used, corresponding different etchants or etch schemes can be used to form a rough surface that includes a plurality of pyramid structures. In some embodiments, the etching process may use anisotropic etching or isotropic etching, a chemical acidic etching process (the etchant is, for example, hydrofluoric acid or nitric acid), or chemical alkaline An etching process (the etchant is, for example, potassium hydroxide or isopropanol) may be used. Here, it should be understood by those skilled in the art that these process conditions are for illustration only and that any suitable process conditions can be used without departing from the scope of the examples.

  In FIG. 1B, after a rough surface including a plurality of pyramid structures is completed, the rough surface of the semiconductor substrate 110 is oxidized to form an oxide layer 150 on the surface of each pyramid structure on the rough surface, and One round structure 132 is formed in a portion that is not oxidized. In one embodiment, an atmospheric pressure plasma (AP) is used to oxidize the surface of the pyramid structure so as to form the oxide layer 150. The power of the atmospheric pressure plasma is 1 to 2.5 KW, for example, 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, such as a thermal oxidation process, can be used to oxidize the surface of the pyramid structure, such as to form oxide layer 150.

  In FIG. 1C, the oxide layer 150 formed on the surface of the pyramid structure is removed, and the round structure 132 of the valley portion 130 is exposed. In one embodiment, wet etching is used and the etchant includes HF, HCl, or a combination thereof. Dry etching or reactive ion etching (RIE) can also be used. In one embodiment, the etching process is Over Etching to ensure that the oxide layer 150 is completely removed.

  FIG. 1D is an enlarged schematic diagram showing the round structure 132 of the valley. The valley round structure 132 has a radius of curvature (rv) of 25-500 nm, for example 50 nm, 100 nm, 150 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm or 450 nm, preferably 100-350 nm. Note that the round structure 132 of each valley 130 is already formed when the oxide layer 150 is formed, and the round structure 132 is exposed after the oxide layer 150 is removed by etching.

  If the valleys 130 between the bottoms of the pyramid structure are too narrow after roughening etching to form a plurality of pyramid structures, metal impurities are likely to remain therein, and are not easily removed in subsequent processes. Since the metal impurities have an influence on the photoelectric conversion efficiency and open circuit voltage (Voc) of the solar cell, the radius of curvature of the round structure 132 of the valley 130 cannot be made too small. If the curvature radius of the round structure 132 of the valley 130 between the bottoms of the pyramid structure is too large, the photoelectric conversion efficiency is lowered. This is because when the uneven surface morphology of the pyramid structure is oxidized, a large stress is generated in the semiconductor substrate 110 due to the expansion of the volume, and when these stresses exceed the critical shear stress of the semiconductor substrate 110 surface, dislocation type defects are formed. This is because the recombination probability of carriers is increased and the photoelectric conversion efficiency of the solar cell is further reduced.

  Table 1 is the efficiency data of the solar cell obtained by one example of the present invention. The comparison group is a solar cell having no round structure in the valley portion 130, the experimental group is a solar cell having a round structure 132 in the valley portion 130, and the method for oxidizing the surface of the pyramid structure has a power of 1.6 kW. This method uses atmospheric pressure plasma. As can be seen from Table 1, in the solar cell having the round structure 132 in the valley portion 130, the average photoelectric conversion efficiency is improved by 0.11%, and the open circuit voltage is improved by 0.003V.

  As shown in FIG. 2, after removing the oxide layer 150 formed on the surface of the pyramid structure, a doping process is performed on the process surface of the semiconductor substrate 110 so that an emitter layer 260 is formed in the semiconductor substrate in the vicinity of the process surface. It can be performed. The conductivity type of the dopant used in the doping process is different from that of the semiconductor substrate 110. In one embodiment, the semiconductor substrate 110 is P-type but the dopant is N-type, for example, a single crystal silicon solar cell or In the polysilicon solar cell, the semiconductor substrate 110 is P-type, but the dopant may be N-type phosphorus. In another embodiment, the semiconductor substrate 110 is N-type but the dopant is P-type. For example, in a heterojunction solar cell, the semiconductor substrate 110 is N-type but the dopant is P-type boron. It may be. The emitter layer 260 can be any conventional emitter, such as a selective emitter.

  In one embodiment, the antireflection layer 270 may be formed on the upper surface of the emitter layer 260 after the emitter layer 260 is formed so as to increase the light absorption of the solar cell and further improve the conversion efficiency of the solar cell. The type of 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. The anti-reflective layer 270 can be deposited on the emitter layer 260 by plasma enhanced chemical vapor deposition (PECVD) or other conventional manner.

  In one embodiment, a plurality of electrodes 280 that contact the emitter layer 260 can be formed after the antireflection layer 270 is formed, and the electrodes 280 can be any conventional electrode, such as a finger electrode. In one embodiment, the electrode is formed by applying a metal paste to the chip with a screen printer and then burning at high temperature.

  The merit of the embodiment of the present invention is a solar cell that has a round structure in the valley between the bottoms of the pyramid structure, and can reduce the residual of metal impurities and improve the photoelectric conversion efficiency and the open circuit voltage. It is in.

  Since a plurality of embodiments have been schematically described above, those skilled in the art can better understand each of the disclosed portions. Those skilled in the art will understand that other synthesis and structures need to be designed or modified on this basis to implement embodiments having similar objectives and / or advantages similar to this introduction. Those skilled in the art will also understand that any substitutions, replacements and modifications can be made without departing from the spirit and scope of the present invention.

DESCRIPTION OF SYMBOLS 100 Solar cell 110 Semiconductor substrate 120 Tip 130 Valley 150 Oxidation layer 132 Valley 200 shown by the dotted line block Solar cell 210 Semiconductor substrate 260 Emitter layer 270 Antireflection layer 280 Electrode

Claims (10)

A semiconductor substrate having a light incident surface having a plurality of protrusion structures each including a tip 120, and having a trough with a radius of curvature of 25 to 500 nm between any adjacent protrusion structures;
An emitter layer located in the semiconductor substrate in proximity to the light incident surface;
An electrode located on the semiconductor substrate;
Solar cell provided.   2. The solar cell according to claim 1, wherein the solar cell is a heterojunction solar cell, and the emitter layer is P-type doping of boron.   The solar cell according to claim 2, further comprising a reflective layer covering the emitter layer. Providing a semiconductor substrate having a process surface;
Performing a roughening etch on the process surface to form a plurality of protrusion structures, and having valleys between any adjacent protrusion structures;
Oxidizing the surface of the protruding structure to form an oxide layer to form a rounded structure in the non-oxidized portions of the valleys;
Removing the oxide layer to expose the rounded structure;
The manufacturing method of the solar cell containing this.   The solar cell of claim 4, further comprising performing a doping process on the process surface such that an emitter layer is formed in the semiconductor substrate proximate to the process surface after removing the oxide layer. Manufacturing method.   The method for manufacturing a solar cell according to claim 5, further comprising forming an antireflection layer on the emitter layer.   The method for forming the oxide layer according to claim 4, wherein the method for forming the oxide layer includes a step of using atmospheric pressure plasma.   The method for manufacturing a solar cell according to claim 4, wherein the etching of the oxide layer includes a step of using an etchant made of HF, HCl, or a combination thereof.   The method for manufacturing a solar cell according to claim 7, wherein the electric power of the atmospheric pressure plasma is 1 to 2.5 kW.   The method for manufacturing a solar cell according to claim 6, further comprising forming a plurality of electrodes in contact with the emitter layer.

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