Method for making a solar cell

Disclosed is a method for making a solar cell. In the method, there are provided first and second substrates each including first and second faces. There are provided first and second coating devices and a joining device. The first coating device is used to form a transparent electrode layer on the first face of the first substrate. The second coating device is used to form an absorbing layer on the first face of the second substrate. The second substrate is selenized by hot pressing. The joining device is used to join together the first and second substrates by joining the transparent electrode layer with the absorbing layer. The transparent electrode layer is joined with the absorbing layer by hot pressing. Thus, the solar cell is not made by coating one layer on another. Time for making the solar cell is reduced.

BACKGROUND OF INVENTION

1. Field of Invention

The present invention relates to a method for making a solar cell and, more particularly, to a method including the steps of coating various layers of a solar cell on different substrates and joining together the laminates, thus making the solar cell efficiently.

2. Related Prior Art

As the population of the world is growing, the consumption of energy is increasing while the reserve of fossil fuel including gasoline, natural gas and coal is declining. Moreover, the environmental pollution is getting worse. Hence, many efforts are made to use renewable energy. To use various types of the renewable energy, there are various types of devices such as fuel cells, solar cells, wind turbines and damps. Compared with a power plant based on wind turbines or a damp, the cost for constructing a power plant based on solar cells is low and the area of the power plant based on the solar cells is small. Hence, solar energy seems the most promising type of the renewable energy.

Generally, the operation of the solar cells is based on semiconductor materials that generate electricity after they absorb sun light. Based on materials and techniques, the solar cells can be classified as chip-type solar cells and thin-film solar cells. A chip-type solar cell includes a p-type semiconductor silicon chip that goes through superficial etching, p-n junction diffusion, anti-reflection film coating and electrode making by screen printing. There is however a serious problem with the use of a chip-type solar cell. The amount of the electricity generated by a chip-type solar cell is less than the amount of electricity consumed to make it.

On the other hand, a thin-film solar cell includes various films made of various materials that generate electricity after they absorb sun light. For example, referring toFIG. 1, a thin-film solar cell9includes various films formed on a substrate90. To make the solar cell9, a Mo metal layer91is formed on the substrate90before an absorbing layer92is formed on the Mo metal layer91. A CdS layer93is formed on the absorbing layer92before an intrinsic ZnO (“i-ZnO) layer94is coated on the CdS layer93. Then, a ZnO:Al (“AZO”) layer95is formed on the i-ZnO layer94. Finally, an anti-reflection layer96and an external electrode97are formed on the AZO layer95.

Generally, the substrate90can be made of soda-lime glass. The absorbing layer92is made of a p-type semiconductor material such as CIS or CIGS. The AZO layer95can be made of an n-type semiconductor material. That is, the structure of the solar cell is a structure based on a p-n junction. The CdS layer93can be called the “buffering layer” to increase the absorption efficiency. Moreover, because a semiconductor surface is reflective, all of the sun light does not enter the solar cell9. That is, there is loss of sun light. Hence, the anti-reflection layer96can be made of MgF2for example to increase the proportion of the sun light that enters the solar cell9.

SUMMARY OF INVENTION

An objective of the present invention is to provide an efficient method for making a solar cell by coating various layers of a solar cell on different substrates and joining together the laminates.

Another objective of the present invention is to provide an environmentally friendly method for making a solar cell without using Cd.

Another objective of the present invention is to provide an efficient method for making a solar cell by wherein selenizing is conducted by hot pressing.

To achieve the foregoing objective, the method includes the steps of providing first and second substrates, first and second coating devices and a joining device. Each of the first and second substrates includes first and second faces. The first coating device is used to form a transparent electrode layer on the first face of the first substrate. The second coating device is used to form an absorbing layer on the first face of the second substrate. The joining device is used to join together the first and second substrates by joining the transparent electrode layer with the absorbing layer.

In an aspect, the step of forming the transparent electrode layer on the first face of the first substrate includes the step of forming a transparent conductive material layer on the first face of the first substrate, the step of forming a coating-resisting material layer on each of the first and second faces of the first substrate, the step of forming a buffering material layer on the coating-resisting material layer and the transparent conductive material layer, the step of removing the coating-resisting material layer so that the buffering material layer exposes a portion of the transparent conductive material layer, and the step of forming a pattern on the transparent conductive material layer and the buffering material layer to respectively form the transparent electrode layer and the buffering layer so that the transparent electrode layer exposes a portion of the first substrate.

In the previous aspect, the step of forming a pattern on the transparent conductive material layer and the buffering material layer includes the step of using laser scribing.

In another aspect, the step of forming an absorbing layer on the first face of the second substrate includes the step of forming a back electrode-used material layer on the first face of the second substrate, the step of forming a pattern on the back electrode-used material layer to form a back electrode layer that exposes a portion of the second substrate, and the step of forming the absorbing layer on the back electrode layer so that the absorbing layer exposes a portion of the back electrode layer and a portion of the first face of the second substrate.

In another aspect, the step of forming the transparent electrode layer on the first face of the first substrate includes the step of forming a transparent conductive material layer on the first face of the first substrate, the step of forming a coating-resisting material layer on the second face of the first substrate, the step of forming a buffering material layer on the coating-resisting material layer and the transparent conductive material layer, the step of removing the coating-resisting material layer so that the buffering material layer exposes a portion of the transparent conductive material layer, and the step of forming a pattern on the transparent conductive material layer and the buffering material layer to respectively form the transparent electrode layer and the buffering layer so that the transparent electrode layer exposes a portion of the first substrate.

In the previous aspect, the step of forming a pattern on the transparent conductive material layer and the buffering material layer includes the step of using laser scribing.

In another aspect, the step of forming an absorbing layer on the first face of the second substrate includes the step of forming a back electrode-used material layer on the first face of the second substrate, the step of forming a pattern on the back electrode-used material layer to form a back electrode layer that exposes a portion of the second substrate, and the step of forming the absorbing layer on the back electrode layer so that the absorbing layer exposes a portion of the back electrode layer and a portion of the first face of the second substrate.

In another aspect, the step of forming the transparent electrode layer on the first face of the first substrate includes the step of forming a transparent conductive material layer on the first face of the first substrate, the step of forming a coating-resisting material layer on the second face of the first substrate, the step of forming a buffering material layer on the transparent conductive material layer formed on the first face of the first substrate, and the step of forming a pattern on the transparent conductive material layer and the buffering material layer to respectively form the transparent electrode layer and the buffering layer. The transparent conductive material layer exposes a portion of the first substrate. The buffering layer exposes a portion of the transparent electrode layer.

In the previous aspect, the step of forming a pattern on the transparent conductive material layer and the buffering material layer includes the step of using laser scribing.

In the previous aspect, the step of forming the buffering material layer includes the step of using chemical bath deposition.

In the previous aspect, the method further includes the step of forming an additional buffering layer on the absorbing layer. The step of forming the absorbing layer and the additional buffering layer on the first face of the second substrate includes the step of forming a back electrode-used material layer on the first face of the second substrate, the step of forming a pattern on the back electrode-used material layer to form a back electrode layer that exposes a portion of the second substrate, the step of forming an absorbing material layer on the back electrode layer so that the absorbing material layer is in contact with the first face of the second substrate, the step of forming an additional coating-resisting material layer on the second face of the second substrate, the step of forming an additional buffering material layer on the absorbing material layer, and the step of forming a pattern on the additional buffering material layer and the additional coating-resisting material layer to respectively form an additional buffering layer and an additional absorbing layer that expose a portion of the back electrode layer.

In another aspect, the step of forming the additional buffering material layer includes the step of using chemical bath deposition.

In another aspect, the step of forming the conductive paste between the first and second substrates includes the step of using a screen printing step or a dispensing step.

In another aspect, the step of joining together the first and second substrates includes the step of using hot pressing.

In another aspect, the method further includes the step of providing an isolative layer between the first and second substrates.

In another aspect, the joining device includes a positioning module and a hot pressing module. The positioning module is used for taking a positioning step for positioning the first substrate relative to the second substrate and providing a positioning signal based on the positioning step. The hot pressing module is used for receiving the positioning signal and accordingly taking a hot pressing step to join together the first and second substrates. The first face of the first substrate is in contact with the first face of the second substrate.

In another aspect, the step of joining together the first and second substrates by hot pressing includes the step of forming an absorbing layer on the first substrate, the step of forming a buffering layer on the absorbing layer formed on the first substrate, the step of forming a transparent electrode layer on the second substrate, the step of forming a buffering layer on the transparent electrode layer formed on the second substrate, and the step of joining the buffering layer formed on the absorbing layer formed on the first substrate with the buffering layer formed on the transparent electrode layer formed on the second substrate by hot pressing.

In another aspect, in the step of joining together the first and second substrates by hot pressing, a buffering layer is formed on the transparent electrode layer formed on the first substrate, and the buffering layer is joined with the second substrate by hot pressing. Alternatively, a buffering layer is formed on the absorbing layer formed on the second substrate, and the buffering layer is joined with the first substrate by hot pressing.

In another aspect, in the step of joining together the first and second substrates, the first substrate is provided with material layers that can be joined together by hot pressing to form a buffering layer, and the buffering layer is joined with the second substrate. Alternatively, the second substrate is provided with material layers that can be joined together by hot pressing to form a buffering layer, and the buffering layer is joined with the first substrate.

In another aspect, the step of joining together the first and second substrates by hot pressing includes the step of forming a buffering layer on the transparent electrode layer formed on the first substrate, the step of forming a buffering layer on the absorbing layer formed on the second substrate, and the step of joining together the buffering layers by hot pressing.

In another aspect, an absorbing layer is hot pressed against a layer of selenium so that the absorbing layer is selenized.

DETAILED DESCRIPTION OF EMBODIMENTS

Referring toFIGS. 2 and 3, there is shown a system1for realizing a method for making a solar cell200according to the present invention. The system1includes a first coating device10, a second coating device12and a joining device14. The first coating device10is used to coat a first substrate210with a transparent electrode layer230and a buffering layer250. The first substrate210is formed with two opposite faces212and214. The transparent electrode layer230and the buffering layer250are located on the face212.

The second coating device12is used to coat a second substrate220with a back electrode layer240and an absorbing layer260. The second substrate220is formed with two opposite faces222and224. The back electrode layer240and the absorbing layer260are located on the face222.

The joining device14is used to join the first substrate210with the second substrate20. The face212is in contact with the face222. In practice, the joining device14can include a positioning module140and a hot pressing module142. The positioning module140is used to position the first substrate210relative to the second substrate220and provide a positioning signal based on the positioning. The hot pressing module142is connected to the positioning module140. The hot pressing module142is used to receive the positioning signal and hot press the first substrate210against the second substrate220, thus joining the first substrate210with the second substrate220.

Preferably, the first coating device10and the second coating device12synchronously execute their tasks. After the coating, the first coating device10provides the first substrate210to the joining device14, and the second coating device12provides the second substrate220to the joining device14. The laminate including the first substrate210is taken as the first laminate20(FIG. 4), and the laminate including the second substrate220is taken as the second laminate22(FIG. 4). The first laminate20can be joined with the second laminate22to provide the solar cell200.

To further describe, in detail, the structures of the first laminate20and the second laminate22and how the solar cell200can be made, steps taken to make the solar cell200will be described later.

Referring toFIG. 4, there is shown a method for making the solar cell200according to a first embodiment of the present invention. Steps represented by a-1to a-5are taken to make the first laminate20, and steps represented by b-1to b-4are taken to make the second laminate22.

At a-1, a proper plastic material is chosen for the first substrate210.

At a-2, a transparent conductive material layer232is formed on the face12of the first substrate210. The transparent conductive material layer232includes an AZO layer and an i-ZnO layer. The AZO layer can be made of a n-type semiconductor material while the i-ZnO layer can be made of a non-dosed semiconductor material. Alternatively, the transparent conductive material layer232can be made of indium-tin oxide (“ITO”), indium-zinc oxide (“IZO”), indium-tin-zinc oxide, HfO2, ZnO, Al2O3, aluminum-tin oxide, aluminum-zinc oxide, cadmium-tin oxide and/or cadmium-zinc oxide. Preferably, the transparent conductive material layer232includes the AZO layer and the i-ZnO layer. However, the components of the transparent conductive material layer232are not limited to those described above.

At a-3, a coating-resisting material layer280is formed on the face214of the first substrate210while another coating-resisting material layer280is formed on the transparent conductive material layer232. The coating-resisting material layers280can be made of a metal or non-metal material. The coating-resisting material layers280can be provided by adhesion, deposition, vapor coating or sputtering. Alternatively, the coating-resisting material layers280can be made of a photo-resist material. The coating-resisting material layers280are used to prevent a buffering material from contaminating the face214of the first substrate210and at least one portion of the transparent conductive material layer232in the following steps.

At a-4, a buffering material layer252is formed on the transparent conductive material layer232. At first, the buffering material layer252covers the transparent conductive material layer232and the coating-resisting material layer280. Then, the coating-resisting material layer280is removed so that the buffering material layer252exposes a portion of the transparent conductive material layer232. The buffering material layer252can be formed by spay pyrolysis, chemical bath deposition (“CBD”) or any other proper means. CBD is preferred. That is, while the buffering material layer252is formed on the transparent conductive material layer232by CBD, a pattern is made on the buffering material layer252via the coating-resisting material layer280so that the buffering material layer252is only formed on an predetermined portion of the transparent conductive material layer232.

At a-5shown inFIG. 4, a pattern is made on the transparent conductive material layer232and another pattern is made on the buffering material layer252. The transparent conductive material layer232exposes a portion of the first substrate210. The patterns are made on the transparent conductive material layer232and the buffering material layer252by laser scribing. Thus, the transparent conductive material layer232at A-4is turned into the transparent electrode layer230at A-5while the buffering material layer252at A-4is turned into the buffering layer250at A-5. The first laminate20of the solar cell200is made after the steps represented by a-1to a-5are taken.

Referring toFIG. 4, to make the second laminate22, at b-1, the second substrate220is provided. The second substrate220can be made of stainless steel, aluminum, TiO2, soda-lime glass, polymer or any other proper material.

At b-2, a back electrode-used material layer242is formed on the face222of the second substrate220. The back electrode-used material layer242can be made of a material for excellent ohm contact with the absorbing layer260. For example, the back electrode-used material layer242can be a Mo metal film if the absorbing layer260is made of CIS or CIGS. Generally, the absorbing layer260can be made of CuInS2, CuGaS2, CuGaSe2or any other proper material than the CIS and CIGS if the absorbing layer260is a p-type semiconductor.

At b-3, the pattern is made on the back electrode-used material layer242to form the back electrode layer240that exposes a portion of the face222of the second substrate220. The pattern can be formed on the back electrode-used material layer242by laser scribing.

At b-4, the absorbing layer260is formed on the back electrode layer240. The absorbing layer260exposes a portion of the face222of the second substrate220and a portion of the back electrode layer240. The absorbing layer260can be formed by gravure, electro-deposition of a metal layer, tensioned-web slot coating (“TWSC”), ink-jet printing or any other proper means. These means are given for exemplary purposes only, not for limitation. The second laminate22is completed after the steps represented by b-1to b-4are taken.

After the steps represented by a-1to a-5and b-1to b-4are taken, the first laminate20is joined with the second laminate22. At c-1, a film290of conductive paste is provided between the first substrate210and the second substrate220. The first substrate210(or the first laminate20) is joined with the second substrate220(or the second laminate22) by the joining device14. The transparent electrode layer230attached to the first substrate210is electrically connected to the back electrode layer240attached to the second substrate220by the film290of conductive paste. The face212is in contact with the face222. The film290of conductive paste is provided by screen printing silver paste on the second substrate220for example. Means for providing the film290of conductive paste is however not limited to the screen printing of silver paste. Moreover, the first substrate210(or the first laminate20) is joined with the second substrate220(or the second laminate22) by hot pressing for example.

Because the film290of conductive paste electrically connects the transparent electrode layer230to the back electrode layer240, various photovoltaic units200aof the solar cell200are electrically connected to one another in series. Now, the solar cell200is completed. It should be noted that the steps represented by a-1to a-5can be taken synchronously or sequentially with the steps represented by b-1to b-4. That is, the sequence of the forming of the first laminate20and the second laminate22can be determined based on a user's need and is not limited.

As mentioned above, the solar cell200is made by joining the first laminate20with the second laminate22. The first laminate20and the second laminate22can be made synchronously before they are joined together. Therefore, the system1can be used to produce the solar cell200efficiently.

Referring toFIG. 5, there is shown a method for making the solar cell200according to a second embodiment of the present invention. The steps represented by a-1to a-5are taken to make the first laminate20, and the steps represented by b-1to b-4are taken to make the second laminate22. The second embodiment is like the first embodiment except using a dispensing robot to provide a dot291of conductive paste on the second substrate220at the step represented by c-1. The dot291of conductive paste is provided on the second substrate220for exemplary purposes, not for limitation. Hence, the method shown inFIG. 5can be used to make the solar cell200. The method shown inFIG. 5exhibits the same advantages as the method shown inFIG. 4.

Referring toFIG. 6, there is shown a method for making the solar cell200according to a third embodiment of the present invention. The steps represented by a-1to a-5are taken to make the first laminate20, and the steps represented by b-1to b-4are taken to make the second laminate22. The third embodiment is like the first embodiment except including two steps instead of the steps represented by a-3and a-4as shown inFIG. 4.

At a-3shown inFIG. 6, a coating-resisting material layer280is provided on the face214of the first substrate210only. The coating-resisting material layer280can be made of a metal or non-metal material. The coating-resisting material layer280can be provided by adhesion, deposition, vapor coating or sputtering. Alternatively, the coating-resisting material layer280can be made of a photo-resist material. The coating-resisting material layer280is used to prevent a buffering material from contaminating the face214of the first substrate210and at least one portion of the transparent conductive material layer232in the following steps.

At a-4shown inFIG. 6, a buffering material layer252is formed on the face212of the first substrate210, and a pattern is formed on the buffering material layer252synchronously so that the buffering material layer252exposes at least one portion of the transparent conductive material layer232. The buffering material layer252is formed by spray pyrolysis, CBD or any other proper means. Preferably, spray pyrolysis is used. Moreover, the pattern is formed on the buffering material layer252by laser scribing for example so that the buffering material layer252exposes at least one portion of the transparent conductive material layer232. That is, the pattern is defined by the laser scribing at the step represented by a-4inFIG. 6while the pattern is defined by the coating-resisting material layer280at the step represented by a-4inFIG. 4.

As discussed above, the method shown inFIG. 5can be used to make the solar cell200. The method shown inFIG. 6exhibits the same advantages as the method shown inFIG. 4.

Referring toFIG. 7, there is shown a method for making the solar cell200according to a fourth embodiment of the present invention. The steps represented by a-1to a-5are taken to make the first laminate20, and the steps represented by b-1to b-4are taken to make the second laminate22. The fourth embodiment is like the third embodiment except using a dispensing robot to provide a dot291of conductive paste on the second substrate220at the step represented by c-1. The dot291of conductive paste is provided on the second substrate220for exemplary purposes, not for limitation. Hence, the method shown inFIG. 7can be used to make the solar cell200. The method shown inFIG. 7exhibits the same advantages as the method shown inFIG. 6.

Referring toFIG. 8, there is shown a method for making the solar cell200according to a fifth embodiment of the present invention. The steps represented by a-1to a-5are taken to make the first laminate20, and the steps represented by b-1to b-4are taken to make the second laminate22. The fifth embodiment is like the third embodiment except using a different process for making the second laminate22.

At b-1, the second substrate layer220is provided. The second substrate220can be made of stainless steel, aluminum, TiO2, soda-lime glass, polymer or any other proper material.

At b-2, the back electrode-used material layer242is formed on the face222of the second substrate220. The back electrode-used material layer242can be made of a material for excellent ohm contact with the absorbing layer260. For example, the back electrode-used material layer242can be a Mo metal film if the absorbing layer260is made of CIS or CIGS. Generally, the absorbing layer260can be made of CuInS2, CuGaS2, CuGaSe2or any other proper material than the CIS and CIGS if the absorbing layer260is made of a p-type semiconductor material.

At b-3, the pattern is made on the back electrode-used material layer242to form the back electrode layer240that exposes a portion of the face222of the second substrate220. The pattern can be formed on the back electrode-used material layer242by laser scribing.

At b-4, an additional absorbing material layer262is formed on the back electrode layer240. The additional absorbing material layer262is in contact with a portion of the face222of the second substrate220. The additional absorbing material layer262can be formed by gravure, electro-deposition of a metal layer, tensioned-web slot coating (“TWSC”), ink-jet printing or any other proper means. These means are given for exemplary purposes only, not for limitation. The second laminate22is completed after the steps represented by b-1to b-4are taken.

At b-5, an additional coating-resisting material layer310is formed on the face224of the second substrate220. The additional coating-resisting material layer310is formed on the face224of the second substrate220shown inFIG. 8like the coating-resisting material layer280is formed on the face224of the second substrate220shown inFIG. 4.

At b-6, an additional buffering material layer322is formed on the absorbing material layer262. The additional buffering material layer322is formed in the same manner as the buffering material layer252is formed.

At b-7, a pattern is formed on each of the buffering material layer322and the absorbing material layer262to form an additional buffering layer320and an additional absorbing layer260that expose at least one portion of the back electrode layer240. Preferably, the additional buffering material layer322and the additional absorbing material layer262are made by laser scribing. After the steps represented by b-1to b-7are taken, the second laminate22is completed.

After the steps represented by a-1to a-5and b-1to b-7are taken, the first laminate20is joined with the second laminate22. At c-1, a film290of conductive paste is provided between the first substrate210and the second substrate220. The first substrate210(or the first laminate20) is joined with the second substrate220(or the second laminate22) by the joining device14. The transparent electrode layer230attached to the first substrate210is electrically connected to the back electrode layer240attached to the second substrate220by the film290of conductive paste. The face212is in contact with the face222. The film290of conductive paste is provided by screen printing silver paste on the second substrate220for example. Means for providing the film290of conductive paste are however not limited to the screen printing of silver paste. Moreover, the first substrate210(or the first laminate20) is joined with the second substrate220(or the second laminate22) by hot pressing for example.

Because the film290of conductive paste electrically connects the transparent electrode layer230to the back electrode layer240, various photovoltaic modules200aof the solar cell200are electrically connected to one another in series. Now, the solar cell200is completed. It should be noted that the steps represented by a-1to a-5can be executed synchronously or asynchronously with the steps represented by b-1to b-7. That is, the sequence of the forming of the first laminate20and the second laminate22can be determined based on a user's need and is not limited.

As mentioned above, as shown inFIG. 8, the solar cell200is made by joining the first laminate20with the second laminate22. The first laminate20and the second laminate22can be made synchronously before they are joined together. Therefore, the system1can be used to produce the solar cell200efficiently.

It should be noted that the methods shown inFIGS. 4 to 8can be realized in a non-vacuum continuous production system. Moreover, the foregoing methods are described in relation to a CIGS solar cell for exemplary purposes, not for limitation.

It should also be noted that an isolative layer340can be provided between the first substrate210and the second substrate220after joining the first laminate20with the second laminate22by hot pressing.

Referring toFIG. 9, there is shown a selenizing step of the method of the present invention. Preferably, a transparent conductive material layer420is formed on a first substrate400before an i-ZnO layer440is formed on the transparent conductive material layer420. A zinc layer460is formed on the i-ZnO layer440before a selenium layer480is formed on the zinc layer460. Thus, a first portion40of the CIGS solar cell is made. Then, a second substrate410is substantially coated with a back electrode layer430of Mo and a CIGS absorbing layer450. Thus, a second portion41of the CIGS solar cell is made. Finally, the selenium layer480of the first portion40of the CIGS solar cell is joined with the absorbing layer450of the second portion41of the CIGS solar cell by hot pressing so that the absorbing layer450is selenized by reaction with the selenium layer480. By hot pressing, the selenium layer480can further be joined with a zinc layer460to form the buffering layer of the solar cell and further joined with the absorbing layer450to form a CIGS solar cell. The description referring toFIG. 8is given in relation to a CIGS solar cell for exemplary purposes, not for limitation.

Referring toFIG. 10, there is shown a hot pressing step according to a sixth embodiment of the present invention. A transparent electrode layer61is formed on a first substrate60before a buffering layer62is formed on the transparent electrode layer61. A back electrode layer51is formed on a second substrate50before an absorbing layer52is formed on the back electrode layer51. Then, the buffering layer62is joined with the absorbing layer52by hot pressing so that the second substrate50and the first substrate60are joined together to form a solar cell. Alternatively, the buffering layer62can be formed on the absorbing layer52attached to the second substrate50before the buffering layer62is joined with the transparent61attached to the second substrate60by hot pressing.

Referring toFIG. 11, there is shown a hot pressing step according to a seventh embodiment of the present invention. A buffering layer62ais formed on the transparent electrode layer61attached to the first substrate60while another buffering layer53ais formed on the absorbing layer52attached to the second substrate50. Then, the buffering layer53ais joined with the buffering layer62aby hot pressing so that the second substrate50is joined with the first substrate60to form a solar cell. The buffering layer62aor53acan be made of ZnSe, CdS, ZnS or In2S3. Alternatively, the buffering material layer can be made of cadmium and phosphor that can react with each other to form the CdS of the buffering layer by hot pressing. Alternatively, the buffering material layer can be made of zinc and phosphor that can react with each other to form the ZnS of the buffering layer by hot pressing. Alternatively, the buffering material layer can be made of indium and phosphor that can react with each other to form the In2S3of the buffering layer by hot pressing. These components of the buffering material layer are only given for exemplary purposes, not for limitation.

As discussed above, with the method of the present invention, the solar cell can efficiently be made by forming the first and second laminates synchronously before the first and second laminates are joined together. Furthermore, the present invention provides the system for realizing the method for making the solar cell.

The present invention has been described via the detailed illustration of the embodiments. Those skilled in the art can derive variations from the embodiments without departing from the scope of the present invention. Therefore, the embodiments shall not limit the scope of the present invention defined in the claims.