Patent Publication Number: US-2019189828-A1

Title: Method and device for film removing process

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application is based on and claims the priority of the Chinese patent application No. 201711377087.4 filed on Dec. 19, 2017, which is incorporated herein by reference in its entirety. 
     FIELD 
     The present disclosure relates to the field of photovoltaic technology, and in particular to a method and a device for film removing process. 
     BACKGROUND 
     Photovoltaic power generation is an acknowledged clean energy. In recent years, photovoltaic power generation has been strongly supported by national policies. The film-removing photovoltaic module is widely used in combination with buildings and automobiles, since it can both generate electricity and focus light, such as BIPV (Building Integrated Photovoltaic), and BAPV (Building Attached Photovoltaic). Currently, film-removing of thin film solar cells is mostly accomplished in the way of laser scribing. In other words, a laser is used to remove a proportion of the film layer whose film is not removed so as to achieve the film-removing effect; however, the conventional laser film-removing scribing is typically implemented by scribing while using a motor to drag a laser head, or by scribing in a reciprocating motion of the cell in the case that the laser beam is immobilized. These two scribing ways are both subject to the limitation of the ability of mechanical movement. In this case, the scribing speed can only reach 1000 to 2000 mm per second (mm/s), while the light spot diameter or light spot width is generally limited in a range from 50 microns (μm) to 100 μm. Therefore, the rate of film removing is low. On the other hand, in the conventional laser film-removing scribing, a plurality of laser heads are used simultaneously for processing in order to improve the rate of film removing, and chromatic aberrations are likely to occur in different processing areas due to the differences in the performances of individual lasers. 
     SUMMARY 
     According to embodiments of the present disclosure, there are provided a method and a device for film removing process, which can improve the efficiency of film removing process without generating chromatic aberrations. 
     According to an embodiment of the present disclosure, there is provided a device for film removing process, which includes: an optical assembly, wherein the optical assembly includes: 
     a laser generator for generating a laser beam; 
     a first scanning mirror for reflecting the laser beam; 
     a second scanning mirror for reflecting the laser beam reflected by the first scanning mirror; and 
     a focusing mirror for focusing the laser beam reflected by the second scanning mirror onto a thin film solar cell for film removing process; 
     wherein the device for film removing process further includes a processor and a memory in which instructions are stored, and the following steps are implemented when the instructions are executed by the processor: 
     moving the thin film solar cell or the optical assembly to a designated position, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the thin film solar cell. 
     Optionally, the power of the laser generator is greater than or equal to a preset power. 
     Optionally, the first scanning mirror and the second scanning mirror are scanning oscillating mirrors. 
     Optionally, a focal length of the focusing mirror is greater than or equal to a preset focal length. 
     Optionally, the thin film solar cell includes one or more preset areas, each of which is less than or equal to a scanning range of the first scanning mirror and the second scanning mirror. 
     The following steps are implemented when the instructions are executed by the processor: 
     moving the thin film solar cell or the optical assembly to a designated position, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the current preset area. 
     Optionally, the following steps are further implemented when the instructions are executed by the processor: 
     moving the thin film solar cell or the optical assembly to another designated position after the film removing process on the current preset area is completed, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on another preset area until the film removing process is completed on all the preset areas. 
     According to an embodiment of the present disclosure, there is provided a method for film removing process, which includes: 
     moving a thin film solar cell or an optical assembly to a designated position; and 
     controlling a first scanning mirror and/or a second scanning mirror to be deflected so as to perform a film removing process on the thin film solar cell, wherein the optical assembly includes a laser generator, the first scanning mirror, the second scanning mirror and a focusing mirror, a laser beam generated by the laser generator is reflected by the first scanning mirror and the second scanning mirror, and the reflected laser beam is focused by the focusing mirror onto the thin film solar cell for film removing process. 
     Optionally, the method further includes: 
     dividing the thin film solar cell into one or more preset areas, each of which is less than or equal to a scanning range of the first scanning mirror and the second scanning mirror; and wherein 
     controlling a first scanning mirror and/or a second scanning mirror to be deflected so as to perform a film removing process on the thin film solar cell includes: 
     controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the current preset area. 
     Optionally, the method further includes: 
     moving the thin film solar cell or the optical assembly to another designated position after the film removing process is completed on the current preset area, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on another preset area until the film removing process is completed on all the preset areas. 
     As compared with the related art, the device according to the embodiment of the present disclosure includes: an optical assembly, wherein the optical assembly includes: a laser generator for generating a laser beam; a second scanning mirror for reflecting the laser beam reflected by a first scanning mirror; the first scanning mirror for reflecting the laser beam; and a focusing mirror for focusing the laser beam reflected by the second scanning mirror onto a thin film solar cell for film removing process. The thin film solar cell includes one or more preset areas, each of which is less than or equal to a scanning range of the first scanning mirror and the second scanning mirror. The device for film removing process further includes a processor and a memory in which instructions are stored, and the following steps are implemented when the instructions are executed by the processor: moving the thin film solar cell or the optical assembly to a designated position, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the current preset area. According to the embodiment of the present disclosure, a pair of scanning mirrors is used to perform a scanning-type film removing process on the thin film solar cell, thus increasing the one-time processing area and improving the rate of film removing. Moreover, the rate of film removing can be increased using a single laser generator and no chromatic aberration is generated. 
     In an alternative embodiment, a laser generator having a power greater than or equal to a preset power is used for film removing process, therefore the light spot size of the laser beam is increased, and the rate of film removing is further improved. 
     Additional features and advantages of the disclosure will be set forth in the following description, which in part become apparent from the description or may be learned through the practice of the disclosure. The objects and other advantages of the disclosure may be realized and obtained through the structures particularly mentioned in the specification, claims as well as the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are used to provide a further understanding of the technical solutions of the present disclosure, and constitute a part of the specification. In conjunction with the embodiments of the present disclosure, the drawings are used to explain the technical solutions of the present disclosure, but are not intended to limit the technical solutions of the present disclosure. 
         FIG. 1  is a schematic structural view of a thin film solar cell according to an embodiment of the present disclosure; 
         FIG. 2  is a schematic view of a conventional method for film removing process; 
         FIG. 3  is a schematic structural view of a device for film removing process according to an embodiment of the present disclosure; 
         FIG. 4  is a schematic view of a thin film solar cell according to an embodiment of the present disclosure; and 
         FIG. 5  is a flow chart of a method for film removing process according to an embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Hereinafter, embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be noted that the embodiments and features in the embodiments of the present disclosure can be combined with each other in any form where no conflicts will be caused. 
     Steps illustrated in the flow chart of the drawing may be executed in a computer system including such as a set of computer-executable instructions. Moreover, although a logical order is shown in the flow chart, the illustrated or described steps may be performed in some situations in an order other than the order described herein. 
     Before the method for film removing process according to an embodiment of the present disclosure is set forth, the structure of the thin film solar cell employing the method is introduced firstly.  FIG. 1  is a schematic structural view of a thin film solar cell according to an embodiment of the present disclosure. As shown in  FIG. 1 , the thin film solar cell includes a back electrode layer  1 , a photovoltaic film layer  2 , a front electrode layer  3 , and a transparent substrate  4  from top to bottom. A typical method for film removing process is to selectively etch and remove the back electrode layer  1  and the photovoltaic film layer  2 , or the back electrode layer  1 , the photovoltaic film layer  2  and the front electrode layer  3 , by using a laser. 
     The conventional method for film removing process is shown in  FIG. 2 . Cell structure scribed lines  221  parallel with the X axis are already present on a thin film solar cell  200 , and the cell structure scribed lines  221  are inherent scribed lines on the thin film solar cell  200 , which are not required to be obtained by performing a film removing process using a laser generator  210 . 
     The film-removing scribed lines  220  parallel with the Y axis on the thin film solar cell  200  are required to be obtained by performing a film removing process using the laser generator  210 . The specific method for film removing process is described substantially as follows. 
     The laser generator  210  is fixed at a position on the Z axis, and a laser beam  211  generated by the laser generator  210  emits light in a fixed direction through a focusing mirror  212 . The thin film solar cell  200  is gripped on a platform which is parallel with the XOY plane. Through a Y axis mechanical movement, the platform can drag the thin film solar cell  200  to move along a direction parallel with the Y axis, thereby generating a film-removing scribed line  220  parallel with the Y axis. After a complete film-removing scribed line  220  parallel with the Y axis is generated, if another film-removing scribed line  220  parallel with the Y axis is required to be generated, the platform has to drag the thin film solar cell  200  to step through a X axis mechanical movement, thereby generating another film-removing scribed line  220  parallel with the Y axis. 
     The conventional method for film removing process is limited by the mechanical movement, and the scribing speed can only be in a range from 1000 to 2000 mm/s. Meanwhile, the diameter or width of the light spot is generally limited in a range from about 50 μm to 100 μm. Therefore, the rate of film removing is low. On the other hand, in the conventional laser film-removing scribing, a plurality of laser heads are used simultaneously for processing in order to improve the rate of film removing, and chromatic aberrations are likely to occur in different processing areas due to the differences in the performances of individual lasers. 
     Referring to  FIG. 3 , according to an embodiment of the present disclosure, there is provided a device for film removing process, which includes: an optical assembly, 
     wherein the optical assembly includes: 
     a laser generator  310  for generating a laser beam; 
     a first scanning mirror  312   a  for reflecting the laser beam; 
     a second scanning mirror  312   b  for reflecting the laser beam reflected by the first scanning mirror  312   a ; and 
     a focusing mirror  313  for focusing the laser beam reflected by the second scanning mirror  312   b  onto a thin film solar cell  300  for film removing process. 
     In an alternative embodiment, the power of the laser generator  310  is greater than or equal to a preset power. For example, the power of the laser generator  310  is in a range from several ten Watts to several hundred Watts. For example, a green laser generator having a power of 100 W and a wavelength of 532 nanometers (nm) is used. 
     A high-power laser generator is used for film removing process, and therefore the light spot size of the laser beam is increased, thus further improving the rate of film removing. 
     In an alternative embodiment, the first scanning mirror  312   a  and the second scanning mirror  312   b  are scanning oscillating mirrors. 
     In an alternative embodiment, the focal length of the focusing mirror  313  is greater than or equal to a preset focal length. For example, the focusing mirror  313  has a focal length of 825 millimeters (mm), such as a model F825 focusing mirror. 
     The device for film removing process describe above further includes a processor and a memory in which instructions are stored, and the following steps are implemented when the instructions are executed by the processor: 
     moving the thin film solar cell or the optical assembly to a designated position, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the solar cell  300 . 
     Since the first scanning mirror  312   a  and the second scanning mirror  312   b  each have a certain scanning range, the processing area at each time cannot be greater than the scanning range when the film removing process is performed. Therefore, in a case that the size of the thin film solar cell  300  is less than or equal to the scanning range of the first scanning mirror  312   a  and the second scanning mirror  312   b , there is no need to divide the thin film solar cell  300 . In a case that the size of the thin film solar cell  300  is greater than the scanning range of the first scanning mirror  312   a  and the second scanning mirror  312   b , the thin film solar cell  300  needs to be divided into two or more preset areas, and then the film removing process is separately performed on each of the preset areas. That is, the first preset area is subject to the film removing process; after completion, the second preset area is subject to the film removing process; after completion, the third preset area is subject to the film removing process, . . . , and so on, until the film removing process is completed on all the preset areas. 
     The method for film removing process on each preset area is described in detail below. 
     Firstly, in a case that the film removing process is performed on the solar cell  300 , a pattern for removing a film may be any pattern. For example, the pattern for removing a film may be a spot, a scribed line, or other patterns, which is not limited in the embodiments of the present disclosure. 
     The case where the pattern for removing a film is a scribed line is described as an example below. 
     Forming a scribed line during the movement of the laser beam  311  needs to satisfy that the overlapping ratio between any two adjacent light spots is greater than or equal to a preset threshold. If the overlapping ratio between two adjacent light spots is less than the preset threshold, two independent light spots are obtained. 
     When the thin film solar cell or the optical assembly is moved to the designated position, the designated position should at least enable the control of the deflection of the first scanning mirror and/or the second scanning mirror to complete the film removing process on the current preset area. The designated position may be any position as long as the film removing process on the current preset area can be completed. For example, in  FIG. 3 , if the film-removing scribed line  320  parallel with the Y axis needs to be obtained, the first scanning mirror  312   a  and the second scanning mirror  312   b  may be firstly adjusted to the zero position, and then the thin film solar cell or the optical assembly is moved to the designated position so that the laser beam is focused onto the upper left corner of the preset area. Then, the first scanning mirror  312   a  and the second scanning mirror  312   b  are controlled to be deflected. 
     As shown in  FIG. 4 , it is assumed that the thin film solar cell includes three preset areas, i.e., a preset area  420   a , a preset area  420   b , and a preset area  420   c  respectively. Ten film-removing scribed lines  320  parallel with the Y axis now need to be scribed in each of the preset area  420   a , the preset area  420   b  and the preset area  420   c . The first scanning mirror  312   a  and the second scanning mirror  312   b  are firstly adjusted to the zero position, and then the thin film solar cell or the optical assembly is moved to the designated position so that the laser beam is focused onto the upper end of the first film-removing scribed line  320  in the preset area  420   a , then the first scanning mirror  312   a  is controlled to remain stationary and the second scanning mirror  312   b  is controlled to be deflected so that the laser beam is gradually moved from the upper end to the lower end of the first film-removing scribed line  320  to complete the film removing process on the first film-removing scribed line  320 . After that, the laser generator  310  is turned off, then the second scanning mirror  312   b  is controlled to remain stationary and the first scanning mirror  312   a  is controlled to be deflected so that the laser beam is moved to the lower end of the second film-removing scribed line  320 . Then, the laser generator  310  is turned on, and the first scanning mirror  312   a  is controlled to remain stationary and the second scanning mirror  312   b  is controlled to be deflected so that the laser beam is gradually moved from the lower end to the upper end of the second film-removing scribed line  320  to complete the film removing process on the second film-removing scribed line  320 . By analogy, the film removing process on ten film-removing scribed lines  320  in the preset area  420   a  is completed. 
     In an alternative embodiment, the following steps are implemented when the instructions are executed by the processor: 
     moving the thin film solar cell or the optical assembly to a designated position, and controlling the first scanning mirror and/or the second scanning mirror to be deflected to perform a film removing process on the current area. 
     In an alternative embodiment, the following steps are implemented when the instructions are executed by the processor: 
     moving the thin film solar cell or the optical assembly to another designated position after the film removing process on the current preset area is completed, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on another preset area until the film removing process is completed on all the preset areas. 
     According to the embodiment of the present disclosure, a pair of scanning mirrors is used to perform a scanning-type film removing process on the thin film solar cell, thus increasing the one-time processing area and improving the rate of film removing. Moreover, the rate of film removing can be increased using a single laser generator and no chromatic aberration is generated. 
     For example, when the scanning range of the first scanning mirror  312   a  and the second scanning mirror  312   b  is from 0×0 mm to 1500×1500 mm, the scribing speed is 15000 mm/s, and the width or diameter of the light spot is 1 mm in film removing process, the rate of film removing can be up to 15,000 square millimeters per second (mm 2 /s). In the conventional method for film removing process, when the diameter of the light spot is 100 μm and the scribing speed is 1500 mm/s, the rate of film removing is 150 mm 2 /s. Therefore, the method for film removing process according to the embodiment of the present disclosure is 100 times faster than the conventional method for film removing process. 
     In addition, patterns, texts and points marking according to an arbitrary figure are realized using the first scanning mirror  312   a  and the second scanning mirror  312   b , and patterns, texts and so on are formed on the thin film solar cell  300 , which is difficult to achieve in the conventional method for film removing process. 
     Finally, due to a fast rate of film removing when a high-power laser generator is used, scribing of lines and removing of the film can be performed quickly by using a single laser head without causing the chromatic aberration problem. 
     Referring to  FIG. 5 , a method for film removing process is provided according to an embodiment of the present disclosure. Since the first scanning mirror  312   a  and the second scanning mirror  312   b  each have a certain scanning range, the processing area at each time cannot be greater than the scanning range when the film removing process is performed. Therefore, in a case that the size of the thin film solar cell  300  is less than or equal to the scanning range of the first scanning mirror  312   a  and the second scanning mirror  312   b , there is no need to divide the thin film solar cell  300 . In a case that the size of the thin film solar cell  300  is greater than the scanning range of the first scanning mirror  312   a  and the second scanning mirror  312   b , the thin film solar cell  300  needs to be divided into two or more preset areas, and then the film removing process is separately performed on each of the preset areas. That is, the first preset area is subject to the film removing process; after completion, the second preset area is subject to the film removing process; after completion, the third preset area is subject to the film removing process, . . . , and so on, until the film removing process is completed on all the preset areas. 
     The method includes the following steps  500  to  501 . 
     In step  500 , a thin film solar cell or an optical assembly is moved to a designated position. 
     In this embodiment, the optical assembly includes a laser generator, a first scanning mirror, a second scanning mirror and a focusing mirror, the laser beam generated by the laser generator is reflected by the first scanning mirror and the second scanning mirror, and the reflected laser beam is focused by the focusing mirror onto the thin film solar cell for film removing process. 
     When the thin film solar cell or the optical assembly is moved to the designated position, the designated position should at least enable the control of the deflection of the first scanning mirror and/or the second scanning mirror to complete the film removing process on the current preset area. The designated position may be any position as long as the film removing process on the current preset area can be completed. For example, in  FIG. 3 , if the film-removing scribed line  320  parallel with the Y axis needs to be obtained, the first scanning mirror  312   a  and the second scanning mirror  312   b  may be firstly adjusted to the zero position, and then the thin film solar cell or the optical assembly is moved to the designated position so that the laser beam is focused onto the upper left corner of the preset area. Then, the first scanning mirror  312   a  and the second scanning mirror  312   b  are controlled to be deflected. 
     In step  501 , the first scanning mirror and/or the second scanning mirror is controlled to be deflected to perform a film removing process on the current preset area. 
     The method for film removing process on each preset area is described in detail below. 
     Firstly, in a case that the film removing process is performed on the solar cell  300 , a pattern for removing a film may be any pattern. For example, the pattern for removing a film may be a spot, a scribed line, or other patterns, which is not limited in the embodiments of the present disclosure. 
     The case where the pattern for removing a film is a scribed line is described as an example below. 
     Forming a scribed line during the movement of the laser beam  311  needs to satisfy that the overlapping ratio between any two adjacent light spots is greater than or equal to a preset threshold. If the overlapping ratio between two adjacent light spots is less than the preset threshold, two independent light spots are obtained. 
     As shown in  FIG. 4 , it is assumed that the thin film solar cell includes three preset areas, i.e., a preset area  420   a , a preset area  420   b , and a preset area  420   c  respectively. Ten film-removing scribed lines  320  parallel with the Y axis now need to be scribed in each of the preset area  420   a , the preset area  420   b  and the preset area  420   c . The first scanning mirror  312   a  and the second scanning mirror  312   b  are firstly adjusted to the zero position, and then the thin film solar cell or the optical assembly is moved to the designated position so that the laser beam is focused onto the upper end of the first film-removing scribed line  320  in the preset area  420   a , then the first scanning mirror  312   a  is controlled to remain stationary and the second scanning mirror  312   b  is controlled to be deflected so that the laser beam is gradually moved from the upper end to the lower end of the first film-removing scribed line  320  to complete the film removing process on the first film-removing scribed line  320 . After that, the laser generator  310  is turned off, then the second scanning mirror  312   b  is controlled to remain stationary and the first scanning mirror  312   a  is controlled to be deflected so that the laser beam is moved to the lower end of the second film-removing scribed line  320 . Then, the laser generator  310  is turned on, and the first scanning mirror  312   a  is controlled to remain stationary and the second scanning mirror  312   b  is controlled to be deflected so that the laser beam is gradually moved from the lower end to the upper end of the second film-removing scribed line  320  to complete the film removing process on the second film-removing scribed line  320 . By analogy, the film removing process on ten film-removing scribed lines  320  in the preset area  420   a  is completed. 
     In an alternative embodiment, controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the thin film solar cell includes: controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on the current area. 
     In an alternative embodiment, the method further includes: 
     moving the thin film solar cell or the optical assembly to another designated position after the film removing process on the current preset area is completed, and controlling the first scanning mirror and/or the second scanning mirror to be deflected so as to perform a film removing process on another preset area until the film removing process is completed on all the preset areas. 
     According to the embodiments of the present disclosure, a pair of scanning mirrors is used to perform the scan-type film removing process on the thin film solar cell, thus increasing the one-time processing area and improving the rate of film removing. Moreover, the rate of film removing can be increased using a single laser generator and no chromatic aberrations is generated. 
     For example, when the scanning range of the first scanning mirror  312   a  and the second scanning mirror  312   b  is from 0×0 mm to 1500×1500 mm, the scribing speed is 15000 mm/s, and the width or diameter of the light spot is 1 mm in film removing process, the rate of film removing can be up to 15,000 square millimeters per second (mm 2 /s). In the conventional method for film removing process, when the diameter of the light spot is 100 μm and the scribing speed is 1500 mm/s, the rate of film removing is 150 mm 2 /s. Therefore, the method for film removing process according to the embodiment of the present disclosure is 100 times faster than the conventional method for film removing process. 
     In addition, patterns, texts and points marking according to an arbitrary pattern are realized using the first scanning mirror  312   a  and the second scanning mirror  312   b , and the patterns, texts and so on are formed on the thin film solar cell  300 , which is difficult to achieve in the conventional method for film removing process. 
     Finally, due to a fast rate of film removing when a high-power laser generator is used, scribing of lines and removing of the film can be performed quickly by using a single laser head without causing the chromatic aberration problem. 
     While the embodiments of the disclosure are disclosed above, the disclosure is only the embodiments adopted for understanding the disclosure, and is not intended to limit the disclosure. Various modifications and alternations on the forms and details of implementation may be made by those skilled in the art without departing from the spirit and scope of the disclosure. Nevertheless, the scope of protection of the disclosure should still be defined by the scope of the appended claims.