CN103367513A - Polycrystalline silicon thin film solar cell and preparation method thereof - Google Patents

Abstract

The invention proposes an n-ZnO/p-Si heterojunction solar cell based on a ZnO nano array and a preparation method thereof. The battery structure is: FTO or AZO transparent conductive glass substrate/ZnO seed layer/N-type ZnO nano-array/P-type polysilicon film/metal electrode. The preparation method is as follows: prepare ZnO seed layer on FTO or AZO transparent conductive glass substrate by sol-gel method or magnetron sputtering, prepare ZnO nano-array on the seed layer by hydrothermal synthesis method, and then use metal induction The P-type polysilicon thin film is deposited on the surface of the nanometer array, and finally the metal electrode is plated to form an n-ZnO/p-Si heterojunction solar cell. This structural feature is that the Si film is fully covered with ZnO nanorods, and the nano-arrays are used to transfer carriers to improve photovoltaic conversion efficiency; N-type ZnO and P-type Si share a group of doping elements, and metal atoms can also be doped by using the metal induction method. Form an effective PN junction.

Description

A kind of polycrystalline silicon thin-film solar cell and its preparation method

technical field

The invention relates to a novel polycrystalline silicon solar cell structure and a preparation method thereof, and belongs to the technical fields of new energy, semiconductor optoelectronics and the like.

Background technique

Solar energy is a renewable energy source with abundant resources. The preparation of solar cells with high conversion efficiency, long life, low production cost, low energy consumption, safe and non-toxic materials and abundant sources is an important direction for the development of solar cells today.

ZnO/Si heterojunction solar cell is a dual energy band structure, which can not only effectively improve the photoelectric conversion efficiency of solar cells, but also effectively reduce the cost of solar cells. In terms of thin-film solar cells, various methods are used at home and abroad to prepare ZnO thin films on Si substrates to prepare ZnO/p-Si, ZnO/n-Si, and n-ZnO/n-Si heterojunction solar cells. So far, the highest photovoltaic conversion efficiency of n-ZnO/n-Si heterojunction is 8.5%, and the highest photovoltaic conversion efficiency of n-ZnO/p-Si heterojunction is 6.8%. There is still room for improvement in theory. In terms of organic solar cells, the photoelectric conversion efficiency of solar cells hybridized with _TiO2 flat films and polymers is only 0.09%, while the solar cells with _TiO2 nanoarrays and ZnO nanoarrays hybridized with polymers prepared by the same process, The highest efficiency reaches 0.29%, which fully reflects the advantages of nano-arrays in improving photovoltaic conversion efficiency.

At present, nano-arrays are used in ZnO/Si heterojunction thin-film solar cells. In terms of structure, ZnO nano-arrays are prepared on Si substrates. At present, there is no structure of depositing polysilicon thin films on the basis of ZnO nano-arrays. In the preparation of the ZnO nanoarray structure on the Si substrate, the contact with the Si substrate is not the real ZnO nanorods, but the ZnO seed layer. There is a high defect density between the ZnO seed layer and Si, which is not conducive to the excitons. Quick separation and transfer. On the contrary, when polysilicon thin films are deposited on ZnO nano-arrays, Si directly nucleates and grows on ZnO nano-rods, and ZnO nano-arrays can directly penetrate into the interior of Si, so that poly-silicon films can fully cover ZnO nano-rods, which not only reduces the gap between the two. The defect density, and greatly increased the contact area between the two, is conducive to the rapid separation of excitons, reducing the probability of recombination.

The invention overcomes the disadvantage of preparing the ZnO nano array structure on the Si substrate in terms of structure, and fully utilizes the advantages of nano rods in improving photovoltaic conversion efficiency. It is proposed to prepare a ZnO seed layer on FTO or AZO transparent conductive glass, grow ZnO nanoarrays on the seed layer, and then deposit a P-type polysilicon film on the basis of the nanoarray to form a ZnO/ Si heterojunction solar energy, the polysilicon film completely covers the ZnO nano-array, gives full play to the role of the nano-array, transmits photo-generated carriers to a greater extent, reduces the interface recombination probability, and improves the output efficiency.

In the present invention, the doping elements required by the N-type ZnO nano-array and the P-type Si thin film are the same or the same group of elements, which can not only form an effective PN junction, improve the open circuit voltage of the battery, but also avoid the Changes in battery performance due to interdiffusion of dopant elements.

There are many methods for preparing polysilicon thin films, which can be divided into direct preparation and indirect preparation. Direct preparation refers to the direct preparation of polysilicon film on the substrate by PECVD, LPCVD or HWCVD, but the growth rate is slow. The growth rate of HWCVD is higher than that of ordinary PECVD, but there is a problem of contamination of high-temperature wire materials. The metal-induced crystallization technology is commonly used in the indirect preparation method. This method does not have high requirements on the substrate. The polysilicon film prepared by metal-induced crystallization mainly depends on the type of metal and crystallization temperature, and the structure of amorphous silicon and the thickness of the metal layer. The factors are irrelevant, and the low requirements on the original conditions of amorphous silicon can simplify the preparation process and reduce production costs, but this technology will introduce metal impurities, which will affect the electrical properties of polysilicon films. Generally, pickling or directional solidification is used to remove metal impurities, but it causes metal pollution and waste of metal materials.

The invention skillfully changes the metal Al pollution in the preparation of the polysilicon thin film induced by the metal into a favorable factor. During metal-induced crystallization, Al and Si on ZnO diffuse, Al diffuses to the outer surface, and Si diffuses to the surface of ZnO nano-arrays to nucleate and grow to form a polysilicon film. The contact between the polysilicon film and the ZnO nano-array has a larger area, which can better transfer carriers and improve the photovoltaic conversion efficiency. The doping of Al into Si is P-type doping, and the doping of ZnO is N-type doping. The doping of Al atoms forms an effective PN heterojunction, which not only improves the open circuit voltage of solar cells, but also the residual metal Al is effective Utilization, to avoid pollution and waste of metal materials.

The combined preparation method of the invention has mature technology in each stage, high feasibility, can be prepared in a large area, has no high-temperature and high-energy-consuming steps, has abundant material sources, and is safe and non-toxic.

Contents of the invention

The present invention proposes a n-ZnO/p-Si heterojunction solar cell based on a ZnO nanoarray, and the technical scheme includes the following steps:

(1) A new type of solar energy structure based on ZnO nanoarrays is adopted, and the structure includes: FTO or AZO transparent conductive glass substrate, ZnO seed layer, N-type ZnO nanoarray, P-type polysilicon thin film, and metal electrodes.

(2) A ZnO seed layer was prepared on the FTO transparent conductive glass substrate by a sol-gel method or a magnetron sputtering method, and then a ZnO nanoarray was prepared by a hydrothermal synthesis method.

(3) Polysilicon films were prepared on ZnO nanoarrays. The polycrystalline silicon thin film is prepared by the method of metal-induced crystallization of the amorphous silicon thin film. A layer of metal is vacuum evaporated on the surface of the ZnO nano-array, and then a layer of amorphous silicon film is deposited by PECVD. After heat treatment and annealing, a polysilicon film is obtained. The P-type polysilicon doping includes B and Al. The crystallized polysilicon film can directly reach the bottom of the nano-array, forming the effect that the polysilicon film fully covers the ZnO nanorods.

(4) Vacuum-deposit a layer of metal on the surface of the polysilicon film as an electrode to prepare the above n-ZnO/p-Si heterojunction solar cell based on ZnO nano-array.

The advantages of the present invention are:

(1) The combined preparation method of the present invention has mature technologies at each stage, high feasibility, large-area preparation, no high-temperature and high-energy-consuming steps, and cheap ordinary glass substrates can be used. The source of materials is abundant, safe and non-toxic.

(2) The present invention utilizes the advantage of nano-array in structure, and overcomes the deficiency that prepares ZnO on Si substrate, adopts to grow on the basis of ZnO nano-array to prepare polysilicon thin film, and ZnO nano-array can directly go deep into the inside of Si thin film, realizes The polysilicon film fully covers the ZnO nanorods, making full use of the unique photoelectric transmission and separation effect of the nanoarray structure on the photogenerated carriers, increasing the contact area between the ZnO nanorods and the polysilicon film, effectively transmitting the photogenerated carriers, reducing the probability of interfacial recombination, and improving output efficiency.

(3) among the present invention, the doping elements required by the N-type ZnO nano-array and the P-type Si film are the same or the same group of elements, which can form an effective PN junction, improve the open circuit voltage of the battery, and avoid the need for preparation or Changes in battery performance caused by interdiffusion of dopant elements during use.

(4) The present invention turns metal-induced metal Al contamination in the preparation of polysilicon thin films into a favorable factor. When the polycrystalline silicon film is prepared by the metal Al induction method, the doping of Al atoms is used. Al is doped into Si as P-type doping, and as ZnO as N-type doping, which is conducive to the formation of an effective PN heterojunction and is beneficial to Increase the open circuit voltage of the solar cell. The remaining metal Al is effectively utilized to avoid contamination of metal materials.

Description of drawings

The accompanying drawings are structural schematic diagrams of the present invention, and the present invention will be further described below in conjunction with the accompanying drawings and specific implementation examples.

Fig. 1 is a kind of structural representation of polysilicon thin-film solar cell based on ZnO nano-array;

Reference signs: 1. FTO transparent conductive glass substrate; 2. ZnO seed layer; 3. N-type ZnO nano-array; 4. P-type polysilicon film; 5. Metal electrode.

Fig. 2 is a schematic diagram of the structure before the annealing of the aluminum induced crystallization process of the implementation case 1;

Reference signs: 1. FTO transparent conductive glass substrate; 2. ZnO seed layer; 3. N-type ZnO nano array; 6. induced metal aluminum; 7. amorphous silicon film.

Fig. 3 is a schematic diagram of the structure after the annealing of the aluminum induced crystallization process of the implementation case 1;

Reference signs: 1. FTO transparent conductive glass substrate; 2. ZnO seed layer; 3. N-type ZnO nano-array; 4. P-type polysilicon film; 8. Aluminum film after annealing.

Detailed ways

The present invention will be further described below by embodiment, and the present invention is by no means limited to stated embodiment:

Example 1:

As shown in Figure 2, using FTO glass as the substrate, the ZnO seed layer is prepared by the sol-gel method, and then the N-type ZnO nanoarray is grown on the seed layer by the hydrothermal synthesis method; a layer of metal is evaporated on the nanoarray Al, PECVD is used to deposit Al-doped amorphous silicon film on the Al film; then a layer of Al is vacuum evaporated on the annealed film to form n-ZnO/p-Si heterojunction solar cells based on ZnO nanoarrays. The zinc ion concentration is 0.005mol/L, the water bath temperature is 60°C, the water bath time is 8h, the PECVD reaction chamber temperature is 300°C, and the annealing heat treatment temperature is 650°C.

As shown in Figure 3, after heat treatment, Al and Si on the ZnO diffuse, Al diffuses to the outer surface, Si diffuses to the ZnO surface, and the polysilicon film contacts with a larger area of the ZnO nanoarray to better transfer carriers and improve photovoltaic performance. conversion efficiency.

Example 2:

FTO glass was selected as the substrate, and the ZnO seed layer was prepared by magnetron sputtering. Then, N-type ZnO nanoarrays were grown on the seed layer by hydrothermal synthesis; a layer of metal Ni was evaporated on the nanoarrays, and a B-doped amorphous silicon film was deposited on the Ni film by PECVD; and then on the annealed film A layer of Al is coated by vacuum coating to form a n-ZnO/p-Si heterojunction solar cell based on ZnO nano-arrays. The zinc ion concentration is 0.015mol/L, the water bath temperature is 70°C, the water bath time is 7h, the PECVD reaction chamber temperature is 350°C, and the annealing heat treatment temperature is 550°C.

Example 3:

FTO glass was selected as the substrate, and the ZnO seed layer was prepared by magnetron sputtering. Then, N-type ZnO nanoarrays were grown on the seed layer by hydrothermal synthesis; a layer of metal Ag was evaporated on the nanoarrays, and B-doped amorphous silicon films were deposited on the Ag film by PECVD; A layer of Cu is plated by vacuum coating to form a n-ZnO/p-Si heterojunction solar cell based on ZnO nano-arrays. The zinc ion concentration is 0.025mol/L, the water bath temperature is 80°C, the water bath time is 5.5h, the PECVD reaction chamber temperature is 400°C, and the annealing heat treatment temperature is 500°C.

Example 4:

FTO glass was selected as the substrate, and the ZnO seed layer was prepared by magnetron sputtering. Then, N-type ZnO nano-arrays were grown on the seed layer by hydrothermal synthesis; a layer of metal Cu was evaporated on the nano-arrays, and a B-doped amorphous silicon film was deposited on the Cu film by PECVD; and then on the annealed film A layer of Pt is coated by vacuum coating to form a n-ZnO/p-Si heterojunction solar cell based on ZnO nano-arrays. The zinc ion concentration is 0.035mol/L, the water bath temperature is 85°C, the water bath time is 4.5h, the PECVD reaction chamber temperature is 450°C, and the annealing heat treatment temperature is 450°C.

Example 5:

AZO glass was selected as the substrate, and the ZnO seed layer was prepared by magnetron sputtering. Then, N-type ZnO nanoarrays were grown on the seed layer by hydrothermal synthesis; a layer of metal Au was evaporated on the nanoarrays, and a B-doped amorphous silicon film was deposited on the Au film by PECVD; A layer of Ag is plated by vacuum coating to form a n-ZnO/p-Si heterojunction solar cell based on ZnO nano-arrays. The zinc ion concentration is 0.04mol/L, the water bath temperature is 90°C, the water bath time is 3h, the PECVD reaction chamber temperature is 500°C, and the annealing heat treatment temperature is 400°C.

Embodiment 6:

AZO glass was selected as the substrate, and the ZnO seed layer was prepared by magnetron sputtering. Then, N-type ZnO nanoarrays were grown on the seed layer by hydrothermal synthesis; a layer of metal Pd was evaporated on the nanoarrays, and a B-doped amorphous silicon film was deposited on the Pd film by PECVD; A layer of Ag is plated by vacuum coating to form a n-ZnO/p-Si heterojunction solar cell based on ZnO nano-arrays. The zinc ion concentration is 0.05mol/L, the water bath temperature is 100°C, the water bath time is 2h, the PECVD reaction chamber temperature is 600°C, and the annealing heat treatment temperature is 350°C.

Claims (10)

1. the multi-crystal silicon film solar battery based on the ZnO nano array is characterized in that, its structure comprises successively: FTO or AZO transparent conducting glass substrate, ZnO inculating crystal layer, N-type ZnO nano array, P type polysilicon membrane, metal electrode.

2. according to right 1 described structure, it is characterized in that, N-type ZnO nano array is directly deeply inner to the Si film, realizes the comprehensive clading ZnO nano rod of polysilicon membrane.

3. according to right 1 described structure, it is characterized in that, the required doped chemical of N-type ZnO nano array and P type Si film is same or with gang's element, can form effective PN junction, improve the open circuit voltage of battery, can avoid again the battery performance that the doped chemical counterdiffusion causes in preparation or use procedure to change.

4. according to right 1 described structure, it is characterized in that, adopt first sol-gel process or magnetron sputtering method making ZnO inculating crystal layer on FTO or AZO transparent conducting glass substrate in the preparation N-type ZnO nano array process, then adopt hydrothermal synthesis method at inculating crystal layer preparation N-type ZnO nano array, the N-type doped chemical comprises B, Al.

5. according to right 1 described structure, it is characterized in that, in the step of the above-mentioned P type polysilicon membrane of preparation, form P type polysilicon membrane by metal-induced crystallization amorphous silicon membrane, thermal anneal process, the P type mixes and comprises B, Al.

6. according to right 5 described preparation methods, it is characterized in that, in the step of the above-mentioned P type polysilicon membrane of preparation, the described metal of inducing comprises Al, Ni, Cu, Au, Ag, Pd.

7. according to right 6 described preparation methods, it is characterized in that, in the step of the above-mentioned P type polysilicon membrane of preparation, if it is that the P type mixes that employing induces metal A l, Al to mix among the Si, mixing among the ZnO is that N-type is mixed, effectively form the PN heterojunction, improve the open circuit voltage of battery.

8. according to right 1 described structure, it is characterized in that, adopt the vacuum evaporation metal electrode, metal electrode comprises Al, Ag, Cu, Pt.

9. according to right 3 described preparation methods, it is characterized in that, zinc ion concentration is between 0.005-0.5mol/L, and bath temperature is between 60-100 ℃, and the water-bath time is between 2-8h.

10. according to right 4 described preparation methods, it is characterized in that, in the step of the above-mentioned P type polysilicon membrane of preparation, the PECVD reaction chamber temperature arranges between 300-600 ℃; Heat treatment temperature is between 350-650 ℃.

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