TWI609500B - Method for fabricating a hetero-junction solar cell - Google Patents

Description

Heterojunction solar cell manufacturing method

The invention relates to a method for manufacturing a battery, in particular to a method for manufacturing a heterojunction solar cell.

Referring to FIG. 1, a conventional bismuth-based heterojunction solar cell includes a substrate having an opposite first surface and a second surface, and a first intrinsic semiconductor layer 11 (ia-Si) formed on the first surface. :H), a p-type germanium semiconductor layer 12 (pa-Si:H) formed on the first intrinsic semiconductor layer 11, and a second intrinsic semiconductor layer 13 formed on the second surface (ia- Si:H), an n-type germanium semiconductor layer 14 (na-Si:H) formed on the second intrinsic semiconductor layer 13, and two layers separately formed on the p-type germanium semiconductor layer 12 and the n-type a transparent conductive layer 15 on the germanium semiconductor layer 14, and two electrodes 16 respectively formed on the two transparent conductive layers 15, the first intrinsic semiconductor layer 11 and the p-type germanium semiconductor layer 12, and the first The two intrinsic semiconductor layers 13 and the n-type germanium semiconductor layer 14 form a photoelectric conversion structure that generates electrons by photoelectric effect when two layers of light are irradiated, so that when light is received, light is photoelectrically converted into a two-layer photoelectric conversion structure to generate a flow of electrons, and then The two transparent conductive layers 15 and the two electrodes 16 are output outward.

One of the problems with the existing bismuth-based heterojunction solar cells is that doping such as p-type doped boron is required when forming the p-type germanium semiconductor layer 12 and/or the n-type germanium semiconductor layer 14. The atom acts as a dopant to become a non-essential impurity range, and the first intrinsic semiconductor layer 11, the p-type germanium semiconductor layer 12, the second intrinsic semiconductor layer 13, and the n-type germanium The semiconductor layer 14 itself is an extremely thin film body, so that dopants may be doped into the first intrinsic semiconductor layer 11 and the second intrinsic semiconductor layer 13 to form a carrier recombination center, which reduces the overall defect. The output efficiency of the base heterojunction solar cell.

At present, one of the solutions proposed by the academic community and the industry is disclosed in, for example, the patent application No. 101137752, before the formation of the p-type germanium semiconductor layer and the n-type germanium semiconductor layer, the low-power hydrogen plasma or After the oxygen plasma purges the first intrinsic semiconductor layer and the surface of the second intrinsic semiconductor layer, the p-type germanium semiconductor layer and the n-type germanium semiconductor layer are formed by plating, so that the occurrence of contamination can be effectively avoided; Low-power hydrogen plasma or oxygen plasma purge cleaning can cause interface defects, have limited effectiveness in improving the defect density caused by doping pollution, and, according to academic and industry research, are applied in this technology. The focus is on low-power (13.56 MHz) hydrogen plasma or oxygen plasma purge. The lower the plasma power, the more the bombardment effect on the surface of the first intrinsic semiconductor layer and the second intrinsic semiconductor layer can be avoided. However, the lower the power, the slower the plating rate does not meet the process efficiency requirements.

Further, for example, the patent application No. 101114082 discloses a PIN microcrystal formed by forming a multi-layered layer on the surface of the first intrinsic semiconductor layer and the second intrinsic semiconductor layer by a mixed gas of a fluoride and a hydride. The structure and the patent application No. 099124025 disclose that the microcrystalline germanium is embedded in the intrinsic semiconductor layer to effectively reduce internal defects, improve the output efficiency of the overall germanium-based heterojunction solar cell, and even the overall production yield. However, the disadvantages are that the additional process is increased, the difficulty of process control is increased, and the production time is also extended, leading to an increase in production cost, which is not conducive to market competition.

Accordingly, it is an object of the present invention to provide a method of fabricating a heterojunction solar cell that reduces film defect density.

Therefore, the manufacturing method of the heterojunction solar cell of the present invention comprises a step (A), a step (B), a step (C), a step (D), and a step (E).

The step (A) forms a first intrinsic semiconductor layer on a first surface of a substrate, and forms a second intrinsic semiconductor layer on a second surface of the substrate opposite to the first surface.

The step (B) uses a plasma having a frequency higher than 25 MHz to form a first oxide layer and a first thickness of less than 5 nm on the first intrinsic semiconductor layer and the second intrinsic semiconductor layer, respectively. Dioxide layer.

In the step (C), a p-type germanium semiconductor layer and an n-type germanium semiconductor layer are respectively formed on the first oxide layer and the second oxide layer.

The step (D) is deposited on the p-type germanium semiconductor layer and the n-type germanium semiconductor layer to form a transparent conductive layer.

In the step (E), an electrode for conducting electricity is formed on each of the transparent conductive layers.

The effect of the invention is that a plasma source having a frequency higher than 25 MHz is deposited on the first intrinsic semiconductor layer and the second intrinsic semiconductor layer with a relatively high plasma density and a low ion bombardment energy to form a low thickness. a first oxide layer and a second oxide layer of 5 nm to reduce the subsequent formation of the p-type germanium semiconductor layer and the n-type germanium semiconductor layer, which may occur on the first intrinsic semiconductor layer and the second intrinsic semiconductor layer Doping pollution can effectively improve the output efficiency of the overall sulfhydryl heterojunction solar cell and reduce the production cost by a relatively simple process, which is conducive to market competition.

Before the present invention is described in detail, it should be noted that in the following description, similar elements are denoted by the same reference numerals.

Referring to FIG. 2, an embodiment of a method for fabricating a heterojunction solar cell of the present invention sequentially performs a step (A), a step (B), a step (C), a step (D), and a step (E). In order to improve the production technology of the existing heterojunction solar cell, the problem of the production cost and the output performance of the overall sulfhydryl heterojunction solar cell cannot be achieved in the production of the heterojunction solar cell as shown in FIG.

As shown in FIG. 3, the heterojunction solar cell produced by the embodiment of the method for fabricating a heterojunction solar cell of the present invention is similar to the existing germanium-based heterojunction solar cell, and includes a first one having an opposite first. a substrate 2 of the surface 21 and a second surface 22, a first intrinsic semiconductor layer 3 (ia-Si:H) formed on the first surface 21, and a layer formed on the first intrinsic semiconductor layer 3 a first oxide layer 9, a p-type germanium semiconductor layer 5 (pa-Si: H) formed on the first oxide layer 9, and a second intrinsic semiconductor layer 4 formed on the second surface 22 (ia) -Si:H), a second oxide layer 10 formed on the second intrinsic semiconductor layer 4, and an n-type germanium semiconductor layer 6 (na-Si:H) formed on the second oxide layer 10, Two layers of transparent conductive layers 7 respectively formed on the p-type germanium semiconductor layer 5 and the n-type germanium semiconductor layer 6, and two electrodes 8 respectively formed on the two transparent conductive layers 7, which a first intrinsic type semiconductor layer 3, a first oxide layer 9 and a p-type germanium semiconductor layer 5, and the second intrinsic type semiconductor layer 4, the second oxide layer 10 and n The 矽-type semiconductor layer 6 forms a photoelectric conversion structure that generates electrons by photoelectric effect when two layers of light are irradiated, so that when light is received, light is photoelectrically converted into a two-layer photoelectric conversion structure to generate a flow of electrons, and then through the two transparent conductive layers 7 and The two electrodes 8 are output to the outside. In particular, the thickness of the first oxide layer 9 and the second oxide layer 10 is extremely thin (not more than 5 nm), so that the light travel, and electrons and carrier tunneling are affected to affect photoelectric conversion, and formation can be avoided. In the process of the p-type germanium semiconductor layer 5 and the n-type germanium semiconductor layer 6, contamination of the first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4 is caused by doping, so that the defect density increases and the whole The problem of reduced output efficiency of the ruthenium-based heterojunction solar cell is described in detail in the description of this embodiment.

Referring to FIG. 2 and FIG. 3, this embodiment of the method for fabricating a heterojunction solar cell of the present invention is to load the substrate 2 into a coating chamber (not shown) of a vacuum coating chamber, and then perform the step (A). The first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4 are formed on the first surface 21 and the second surface 22 of the substrate 2, respectively. In more detail, the step (A) forms the first intrinsic type semiconductor layer 3 by plasma enhanced chemical vapor deposition (PECVD), and thereafter, the movement of the first intrinsic type semiconductor layer 3 is completed. The substrate 2 is turned into an inversion chamber of the vacuum coating chamber, and the substrate 2 of the first intrinsic semiconductor layer 3 is inverted and then transferred into the coating chamber to form a plasma enhanced chemical vapor deposition on the second surface 22 Two intrinsic semiconductor layers 4.

The step (B) uses a plasma having a frequency higher than 25 megahertz (MHz) to form the first oxide having a thickness of less than 5 nm on the first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4, respectively. The layer 9 and the second oxide layer 10, in particular, the step (B) is similar to the step (A), in which the entire semi-finished product is continuously flipped in the inversion chamber and the coating chamber of the vacuum coating chamber.

In more detail, the step (B) is to first maintain the vacuum of the coating chamber of the vacuum coating chamber below 10 ^-6 Torr, preferably below 700 mTorr to 900 mTorr, and to introduce hydrogen gas and a mixed gas of methane (H ₂ /SiH ₄ ), a gas flow ratio of hydrogen (H ₂ ): methane (SiH ₄ ) of between 2 and 25, preferably between 15 and 20, and maintaining the The temperature of the substrate 2 is between 150 degrees and 250 degrees, preferably between 170 degrees and 200 degrees, and the power density of the plasma source is controlled between 10 milliwatts and 100 milliwatts per square centimeter. a plasma source having a frequency between 27.12 MHz and 40.68 MHz, preferably having a power density of between 30 milliwatts and 80 milliwatts per square centimeter and a frequency of 40.68 MHz, deposited to form the first oxide layer 9 and The second oxide layer 10.

In particular, the step (B) produces a plasma of higher density and lower ion bombardment energy at a high oscillation frequency of 27.12 MHz to 40.68 MHz, which can be quickly applied to the first intrinsic semiconductor layer 3 and the second essence. Depositing the first oxide layer 9 and the second oxide layer 10 having a thickness of not more than 5 nm on the semiconductor layer 4, thereby reducing ions of the first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4 during coating The impact of the bombardment effect.

The step (C) forms the p-type germanium semiconductor layer 5 and the n-type germanium semiconductor layer 6 on the first oxide layer 9 and the second oxide layer 10, respectively; similar to the step (A) and the step ( B), successively flipping the whole semi-finished product in the inversion chamber and the coating chamber of the vacuum coating chamber. In detail, when the p-type germanium semiconductor layer 5 is formed in the plating chamber, the first oxide layer 9 can appropriately block the dopant into the first intrinsic semiconductor layer 3, thereby reducing the defect density of the film body. Moreover, since the first oxide layer 9 has a negative charge, the composite probability of the surface carrier and the defects at the interface can be reduced, thereby improving the quality of the film body and effectively improving the photoelectric conversion efficiency; after depositing the p-type germanium semiconductor layer 5, Then, the semi-finished product is moved into the inversion chamber to invert the semi-finished product, and at the same time, water vapor is introduced into the cleaning coating chamber; then the inverted semi-finished product is transferred into the coating chamber, and a similar process is performed to form the n-type germanium semiconductor layer 6.

The step (D) is deposited on the p-type germanium semiconductor layer 5 and the n-type germanium semiconductor layer 6 to form a transparent conductive layer 7, wherein the material of the transparent conductive layer 7 is selected from the group consisting of ZnO, Al: ZnO, B: ZnO, Ga: ZnO, In: ZnO, and the group formed by these.

In this step (E), at least one electrode 8 for conducting electricity is formed on each of the transparent conductive layers 7, respectively.

Compared with the existing ruthenium-based heterojunction solar cells and related process technologies, the method for fabricating the ruthenium-based heterojunction solar cell of the present invention is mainly to rapidly deposit the first oxide layer 9 with a plasma source of high oscillation frequency. The second oxide layer 10 is such that the composite probability of the surface carrier can be reduced and the defect density of the film body can be reduced. Obviously, the process technology of the present invention can improve the quality of the film body without increasing the time cost and the difficulty of the process. Results.

Referring to the table below, in order to clearly illustrate the effectiveness of the method of fabricating the heterojunction solar cell of the present invention, the present invention will be further experimentally tested with different process parameters and verified against existing process techniques.         <TABLE border="1" borderColor="#000000" width="85%"><TBODY><tr><td> </td><td> Oscillation frequency (MHz) </td><td> Power density (mW/cm²) </td><td> substrate temperature (degrees) </td><td> vacuum degree (mtorr) </td><td> defect density (eV<sup >-1</sup>cm^-2) </td></tr><tr><td> Existing Processes</td><td> 13.56 </td><td> </td><td> </td><td> </td><td> 1.4×10¹³</td></tr><tr><td> the present invention </ Td><td> 40.68 </td><td> 60 </td><td> 150 </td><td> 800 </td><td> 2.9×10¹¹</ Td></tr><tr><td> 60 </td><td> 250 </td><td> 800 </td><td> 3.1×10¹²</td ></tr><tr><td> 30 </td><td> 250 </td><td> 400 </td><td> 1.3×10¹²</td> </tr><tr><td> 40 </td><td> 250 </td><td> 400 </td><td> 4.8×10¹¹</td>< /tr><tr><td> 50 </td><td> 250 </td><td> 400 </td><td> 6.0×10¹²</td></ Tr><tr><td> 60 </td><td> 250 </td><td> 400 </td><td> 8.5×10¹¹</td></tr ></TBODY></TABLE>

It can be proved from the above experimental results that the defect density exhibited by the present invention with different power density, substrate 2 temperature, and vacuum degree is obviously far lower than the defect density of the existing process by at least one order of magnitude, thus confirming the present Invented a thin film process for depositing the first oxide layer 9 and the second oxide layer 10 on the first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4 by a plasma source having a frequency of 40.68 MHz, The defect density of the film is indeed lower than that of the conventional film deposited by the plasma source having a frequency of 13.56 MHz and can be avoided in the process of forming the p-type germanium semiconductor layer 5 and the n-type germanium semiconductor layer 6, and further The problem that the subsequently produced ruthenium-based heterojunction solar cell is not contaminated by the intrinsic semiconductor layer causes an increase in defect density and a decrease in output efficiency.

In summary, the method for fabricating a heterojunction solar cell of the present invention deposits the first oxide layer 9 and the second oxide layer 10 on the first essential type by a high frequency (frequency of 40.68 MHz) plasma source. On the semiconductor layer 3 and the second intrinsic semiconductor layer 4, the problem of contamination of the first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4 is reduced, so that defects are generated to reduce the composite probability of surface carriers. For the production of heterojunction solar cells, a good heterojunction can be formed, thereby increasing the lifetime of the photo-generated carriers, thereby improving the film passivation effect and optimizing the photoelectric conversion performance, and at the same time, at a high frequency (frequency of 40.68 MHz). The plasma source acts on the first intrinsic semiconductor layer 3 and the second intrinsic semiconductor layer 4 to form the first oxide layer 9 and the second oxide layer 10, respectively, compared to the existing heterojunction solar cells. (For example, in the patent application No. 101114082), the complexity of the process is further simplified, and at the same time, the yield of the product is improved, so that the object of the present invention can be achieved.

However, the above is only the embodiment of the present invention, and the scope of the invention is not limited thereto, and all the simple equivalent changes and modifications according to the scope of the patent application and the patent specification of the present invention are still Within the scope of the invention patent.

1‧‧‧Substrate

3‧‧‧First essential semiconductor layer

11‧‧‧First Intrinsic Semiconductor Layer

4‧‧‧Second essential semiconductor layer

12‧‧‧p-type germanium semiconductor layer

5‧‧‧p-type germanium semiconductor layer

13‧‧‧Second essential semiconductor layer

6‧‧‧n-type germanium semiconductor layer

14‧‧‧n-type germanium semiconductor layer

7‧‧‧Transparent conductive layer

15‧‧‧Transparent conductive layer

8‧‧‧Electrode

16‧‧‧Electrode

9‧‧‧First oxide layer

2‧‧‧Substrate

10‧‧‧Second oxide layer

21‧‧‧ first surface

A~E‧‧‧Steps

22‧‧‧ second surface

Other features and effects of the present invention will be apparent from the following description of the drawings, wherein: FIG. 1 is a schematic diagram illustrating a conventional bismuth-based heterojunction solar cell; FIG. 2 is a flow chart illustrating the present invention An embodiment of a method of fabricating a heterojunction solar cell; and FIG. 3 is a schematic view of a heterojunction solar cell of the method of fabricating a heterojunction solar cell of the present invention.

A~E‧‧‧Steps

Claims (10)

A method for fabricating a heterojunction solar cell, comprising: (A) forming a first intrinsic semiconductor layer on a first surface of a substrate, and on a second surface of the substrate opposite to the first surface Forming a second intrinsic semiconductor layer; (B) using a plasma having a frequency between 27.12 MHz and 40.68 MHz to form a thickness of less than 5 nm on the first intrinsic semiconductor layer and the second intrinsic semiconductor layer, respectively a first oxide layer and a second oxide layer of the rice; (C) forming a p-type germanium semiconductor layer and an n-type germanium semiconductor layer respectively on the first oxide layer and the second oxide layer; (D) Forming a transparent conductive layer on the p-type germanium semiconductor layer and the n-type germanium semiconductor layer; and (E) forming an electrode for conducting electricity on each of the transparent conductive layers. The method for fabricating a heterojunction solar cell according to claim 1, wherein the step (B) is to form the first oxide layer and the first layer in a vacuum coating chamber maintained at a vacuum of less than 10 ^-6 Torr. Dioxide layer. The method for fabricating a heterojunction solar cell according to claim 2, wherein in the step (B), the vacuum degree of the vacuum coating chamber is maintained between 700 mTorr and 900 mTorr. The method for fabricating a heterojunction solar cell according to claim 2, wherein in the step (B), the vacuum coating chamber is further provided with a mixed gas of hydrogen and helium methane, and a gas flow ratio of hydrogen and helium methane is introduced. Between 2 and 25. The method for fabricating a heterojunction solar cell according to claim 4, wherein in the step (B), H ₂ /SiH _{4 having a} gas flow ratio between 15 and 20 is also introduced into the vacuum coating chamber. . The method for fabricating a heterojunction solar cell according to claim 1, wherein in the step (B), the temperature of the substrate is maintained between 150 degrees and 250 degrees. The method for fabricating a heterojunction solar cell according to claim 1, wherein in the step (B), the power density of the plasma source is controlled to be between 10 milliwatts and 100 milliwatts per square centimeter. The method for fabricating a heterojunction solar cell according to claim 1, wherein in the step (B), the power density of the plasma source is controlled to be between 30 milliwatts and 80 milliwatts per square centimeter. The method for fabricating a heterojunction solar cell according to claim 1, wherein in the step (B), the frequency of the plasma source is controlled to be 40.68 MHz. The method for fabricating a heterojunction solar cell according to claim 1, wherein the step (D) is selected from the group consisting of ZnO, Al: ZnO, B: ZnO, Ga: ZnO, In: ZnO, and the like. The group is formed by material deposition to form the transparent conductive layers.