CN106409922B - Crystal silicon flexible battery and preparation method thereof - Google Patents

Abstract

The invention discloses a crystalline silicon flexible battery and a preparation method thereof. The crystalline silicon flexible battery includes a packaging film and a battery component arranged in the packaging film. The battery component is sequentially composed of an aluminum back electrode layer, a single crystal silicon base layer, a cylindrical silicon array structure layer, a PN junction layer, and a SiNx passivation layer from bottom to top. layer and ITO thin film layer composition. The preparation method includes (1) chemical etching: (2) diffused PN junction: (3) preparation of SiNx passivation layer; (4) plating ITO thin film layer: (5) etching silicon backside; (6) aluminum plating back electrode : (7) encapsulation. The crystalline silicon flexible battery prepared by the invention has a good light-trapping structure and a large light absorption angle, short absorption length of photogenerated carriers, high light absorption efficiency, high photoelectric conversion efficiency, and excellent bending performance.

Description

Crystalline silicon flexible battery and preparation method thereof

technical field

The invention belongs to the field of photovoltaics, and in particular relates to a crystalline silicon flexible battery and a preparation method thereof.

Background technique

Solar cells currently on the market struggle to combine flexibility, high efficiency, and high battery life. Traditional crystalline silicon batteries have high battery efficiency, stability and battery life, but after being made into flexible batteries, cracks and debris are prone to appear in the process of repeated bending, and the repeated bending performance is not good. And new solar cells such as dye-sensitized solar cells, copper indium tin solar cells, etc., can be made into flexible cells with repeated bending, but the life and stability of these cells are poor. Therefore, it is urgent to seek a solar cell that not only has high stability and long life, but also has good repeated bending performance.

Contents of the invention

The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a light-trapping structure with a large light absorption angle, short absorption length of photogenerated carriers, high light absorption efficiency, high photoelectric conversion efficiency and bending performance. Excellent crystalline silicon flexible battery and its preparation method.

In order to solve the problems of the technologies described above, the present invention adopts the following technical solutions:

A crystalline silicon flexible battery, the crystalline silicon flexible battery includes an encapsulation film and a battery assembly arranged in the encapsulation film, the battery assembly consists of an aluminum back electrode layer, a single crystal silicon base layer, and a cylindrical silicon array from bottom to top Structure layer, PN junction layer, SiNx passivation layer and ITO film layer.

In the above crystalline silicon flexible battery, preferably, the diameter of the array unit of the cylindrical silicon array structure layer is 1 μm to 2 μm, the height of the array unit is 2 μm to 4 μm, and the center-to-center distance between adjacent array units is 3 μm to 2 μm. 8 μm; and/or, the junction depth of the PN junction layer is 0.2 μm to 0.42 μm; and/or, in the SiNx passivation layer, the atomic ratio of Si to N (ie 1/x) is between 0.743 and 1.014 Between, the thickness of the SiNx passivation layer is 50nm-80nm.

In the above crystalline silicon flexible battery, preferably, the thickness of the monocrystalline silicon base layer is 20 μm to 100 μm; and/or, the light transmittance T of the ITO thin film layer is > 90%, and the resistivity ρ < 4× 10 ^-4 Ω·cm, and the refractive index n is 2.1 to 2.5.

As a general technical idea, the present invention also provides a method for preparing the above-mentioned crystalline silicon flexible battery, comprising the following steps:

(1) Chemical etching: perform chemical etching on the single crystal silicon, etch out the cylindrical silicon array structure, and obtain the cylindrical silicon array structure layer;

(2) Diffusion: A PN junction is prepared by a diffusion process on the cylindrical silicon array structure layer to obtain a PN junction layer;

(3) Prepare SiNx passivation layer: adopt PECVD process to prepare SiNx passivation layer on PN junction layer;

(4) ITO film coating: on the SiNx passivation layer, the PECVD process is used to plate the ITO film to obtain the ITO film layer (i.e. Sn-doped In ₂ O ₃ film);

(5) Etching the back side of silicon: performing etching and thinning on the back side of monocrystalline silicon retained in step (1) to obtain a monocrystalline silicon base layer;

(6) Aluminum-plated back electrode: aluminum paste is screen-printed on the back of the monocrystalline silicon base layer, and after sintering, an aluminum back electrode layer is obtained;

(7) Encapsulation: Encapsulate the battery components composed of the respective structural layers prepared in steps (1) to (6) to obtain a crystalline silicon flexible battery.

In the above method for preparing a crystalline silicon flexible battery, preferably, in the step (2), the diffusion process includes the following process: first oxidizing at 600°C to 800°C for 3min to 5min in an _O2 and _N2 atmosphere , then pass through POCl ₃ , O ₂ and N ₂ , diffuse at a diffusion temperature of 800°C to 825°C for 3min to 5min, then increase the temperature to 810°C to 835°C, and deep in POCl ₃ , O ₂ and N ₂ Diffuse for 3 minutes to 5 minutes to further push the PN junction deeper.

In the above method for preparing a crystalline silicon flexible battery, preferably, in the step (3), the conditions of the PECVD process are: the vacuum pressure is 180Pa to 230Pa, the coating temperature is 430°C to 450°C, and SiH ₄ and NH ₃ , the gas flow ratio of SiH ₄ and NH ₃ is 4200:500, and the radio frequency power is 3500W-4000W.

In the above method for preparing a crystalline silicon flexible battery, preferably, in the step (6), the sintering process is as follows: first, the aluminum paste is dried at a drying temperature of 100° C. to 200° C. and a drying time of 10 minutes. ～20min, then sintering at 400℃～450℃ for 30min～60min, and then sintering at 600℃～900℃ for 10min～25min to form ohmic contact.

In the above method for preparing a crystalline silicon flexible battery, preferably, in the step (7), the packaging material is polydimethylsiloxane (PDMS).

In the present invention, the thickness of the aluminum back electrode layer is generally 20 μm to 30 μm.

In the present invention, SiNx acts as a passivation layer and a light-absorbing layer. When the refractive index is the smallest, the three-layer refractive index conforms to the following relationship:

Among them, n ₁ is the refractive index of SiNx, n ₀ is the refractive index of single crystal silicon, n ₀ = 2.39, n ₂ is the refractive index of the packaging material PDMS, n ₂ = 1.40, according to formula (1), we can know the refractive index of SiNx , n ₁ = 1.83 The film has the best optical properties, in order to improve the minority carrier lifetime, n ₁ is set between 1.9-2.1;

According to the empirical formula of the refractive index of SiNx and the content ratio of Si and N elements (atomic ratio):

The Si to N ratio (ie 1/x) is between 0.743 and 1.014.

The innovation of the present invention is:

Based on the traditional crystalline silicon battery, the present invention designs a brand-new crystalline silicon battery structure, which can be bent repeatedly, and is a highly efficient flexible battery. The invention is a solar cell with a 3D structure. A PN junction is formed on a cylindrical silicon array structure, which has good light trapping performance, short photocarrier absorption length, high cell efficiency, and a special 3-D microrod structure. The crystalline silicon flexible battery can be bent or repeatedly bent, and it is difficult to generate cracks. The impact of bending on battery performance is very small, and the battery life is longer. Considering that crystalline silicon has a long minority carrier diffusion length and a high exciton recombination rate on the silicon surface, the columnar silicon array structure is optimized, and the scale of the nanorods is set on the order of microns, so as to ensure that this new type of While the battery has relatively high light absorption efficiency and photoelectric conversion efficiency, it reduces the loss caused by surface recombination. After the transparent conductive layer ITO is plated, the present invention has an etching and thinning process, which makes it more suitable for flexible batteries. The invention does not need to weld the grating, reduces the light-enhancing area, simplifies the preparation steps, and is beneficial to increase the production capacity and reduce the cost.

Compared with the prior art, the present invention has the advantages of:

1. The crystalline silicon flexible battery prepared by the present invention has a completely different structural design from the prior art, especially a special 3-D microrod structure (ie, a cylindrical array structure). This special 3-D microrod structure It is difficult to produce cracks when bending or repeated bending, and the impact of bending on battery performance is very small, and the battery life is longer.

2. The crystalline silicon flexible battery prepared by the present invention has higher light absorption efficiency: (1) has a good light trapping structure and a large light absorption angle; (2) short photon absorption length; (3) does not require a grating, which can reduce shading area.

3. The photoelectric conversion efficiency of the crystalline silicon flexible battery prepared by the present invention is higher: (1) short photogenerated carrier absorption length; (2) larger PN junction area, which can carry out photoelectric conversion in time; (3) silicon has Longer minority carrier diffusion length and higher exciton recombination rate on the silicon surface, so the scale of the cylindrical silicon array structure is on the order of microns, which ensures that this new type of cell has higher light absorption efficiency and photoelectric conversion efficiency. At the same time, the loss caused by surface recombination is reduced.

Description of drawings

FIG. 1 is a schematic structural view of the crystalline silicon flexible battery of the present invention.

illustration:

1. Aluminum back electrode layer; 2. Monocrystalline silicon base layer; 3. Cylindrical silicon array structure layer; 4. PN junction layer; 5. SiNx passivation layer; 6. ITO thin film layer; 7. Packaging film.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

All materials and instruments used in the following examples are commercially available.

Example:

A crystalline silicon flexible battery of the present invention, as shown in FIG. 1 , the crystalline silicon flexible battery includes an encapsulation film 7 and a battery assembly disposed in the encapsulation film 7, and the battery assembly consists of an aluminum back electrode layer 1, a single The crystal silicon base layer 2, the cylindrical silicon array structure layer 3, the PN junction layer 4, the SiNx passivation layer 5 and the ITO thin film layer 6 are composed.

In this embodiment, the diameter of the array units of the cylindrical silicon array structure layer 3 is 1.511 μm, the height of the array units is 3.24 μm, and the center-to-center distance between adjacent array units is 5.32 μm. The junction depth of the PN junction layer 4 is 0.252 μm; in the SiNx passivation layer 5 , the atomic ratio of Si to N is 0.875, and the thickness of the SiNx passivation layer 5 is 68 nm.

In this embodiment, the thickness of the monocrystalline silicon base layer 2 is 55 μm; the light transmittance T of the ITO thin film layer 6 is > 90%, the resistivity ρ < 4×10 ^-4 Ω·cm, the refractive index n is 2.1, and the aluminum The thickness of the back electrode layer 1 was 27 μm.

A preparation method of the crystalline silicon flexible battery of the above-mentioned present embodiment, comprising the following steps:

(1) Chemical etching: perform chemical etching on the single crystal silicon to etch out the cylindrical silicon array structure, and obtain the cylindrical silicon array structure layer 3;

(2) Diffusion: a PN junction is prepared on the cylindrical silicon array structure layer 3 by a diffusion process to obtain a PN junction layer 4;

(3) Prepare SiNx passivation layer 5: prepare SiNx passivation layer 5 on PN junction layer 4 by PECVD process, wherein the atomic ratio of Si to N is 0.875;

(4) ITO thin film layer 6: adopt PECVD process to plate ITO thin film on SiNx passivation layer 5, obtain ITO thin film layer 6;

(5) Etching the back side of the silicon: performing etching and thinning on the back side of the single crystal silicon retained in step (1), so that the thickness of the single crystal silicon is 55 μm to obtain the single crystal silicon base layer 2;

(6) Aluminum-plated back electrode: use screen printing to brush aluminum paste on the back side of the monocrystalline silicon base layer 2, and after sintering, obtain the aluminum back electrode layer 1; at this time, the battery assembly is also obtained, that is, step (1) Each structural layer prepared in step (6) together forms a battery assembly;

(7) Encapsulation: the battery assembly is encapsulated with polydimethylsiloxane (PDMS) to form an encapsulation film 7 , and finally a crystalline silicon flexible battery is obtained.

In step (2) of this embodiment, the diffusion process conditions are: first oxidize the single crystal silicon with the cylindrical silicon array structure layer 3 in _O2 and _N2 atmosphere at 800°C for 3min, and then pass _POCl3 , O ₂ and N ₂ , diffused at a diffusion temperature of 825°C for 5 minutes, then raised the temperature to 835°C, and diffused deeply in POCl ₃ , O ₂ and N ₂ atmosphere for 5 minutes to further deepen the PN junction.

In step (3) of this embodiment, the PECVD process conditions for preparing the SiNx passivation layer are: put the intermediate product obtained in step (2) into a PECVD tube to grow the passivation film, and vacuum to a vacuum degree of 226.65Pa , and the temperature of the furnace tube was raised to 430° C., and SiH ₄ and NH ₃ were introduced. The gas flow ratio of SiH ₄ and NH ₃ was 4200 sccm: 500 sccm (in standard cubic centimeters per minute), and the radio frequency power was 3800 W.

In step (6) of this embodiment, the aluminum paste is first dried at a drying temperature of 150° C. for 10 minutes, then sintered at 400° C. for 45 minutes, and then sintered at 800° C. for 10 minutes to form an ohmic contact.

After testing, the crystalline silicon flexible battery (3-D microrod structure) prepared by the present invention has no change in battery efficiency when the incident angle is 0-60°, while the battery efficiency of ordinary crystalline silicon battery drops by 12% when the incident angle reaches 60° . It can be seen that the crystalline silicon flexible battery of the present invention has a good light trapping structure and a large light absorption angle.

The diffusion length of photogenerated carriers in ordinary crystalline silicon cells is the distance from the position where photogenerated carriers are generated to the fine grid line, which depends on the distance of the fine grid, and is on the order of centimeters. And the photogenerated carrier diffusion length of the present invention is the distance from the PN junction to the ITO on the cylindrical silicon array structure (that is, the depth of the PN junction plus the thickness of the SiNx passivation layer), and the depth H of the PN junction can be .2 μm～0.42 μm , generally 0.252 μm, it can be seen that the present invention greatly reduces the absorption length of photogenerated carriers, and can greatly improve the electrical performance of the battery.

The crystalline silicon flexible battery of the present invention has no cracks, bubbles or damage after 200 repeated bending tests, and its battery efficiency is 93% of the initial efficiency.

The above descriptions are only preferred embodiments of the present invention, and do not limit the present invention in any form. Although the present invention has been disclosed above with preferred embodiments, it is not intended to limit the present invention. Any person familiar with the art, without departing from the spirit and technical solutions of the present invention, can use the methods and technical content disclosed above to make many possible changes and modifications to the technical solutions of the present invention, or modify them to be equivalent Variations of equivalent embodiments. Therefore, any simple modifications, equivalent replacements, equivalent changes and modifications made to the above embodiments according to the technical essence of the present invention, which do not deviate from the technical solutions of the present invention, still fall within the protection scope of the technical solutions of the present invention.

Claims (5)

1. a kind of crystal silicon flexible battery, which is characterized in that the crystal silicon flexible battery includes encapsulating film and in encapsulating film Battery component, the battery component is from the bottom to top successively by aluminum back electrode layer, monocrystal silicon substrate layer, cylindrical silicon array structure Layer, PN junction layer, SiNx passivation layers and ito thin film layer composition；

A diameter of 1 μm~2 μm of the array element of the cylindrical silicon array structure layer, a height of 2 μm~4 μm of array element, Center spacing between adjacent array element is 3 μm~8 μm；The junction depth of the PN junction layer is 0.2 μm~0.42 μm；The SiNx In passivation layer, for the atomic ratio of Si and N between 0.743 and 1.014, the thickness of the SiNx passivation layers is 50nm~80nm；

The thickness of the monocrystal silicon substrate layer is 20 μm~100 μm.

2. crystal silicon flexible battery according to claim 1, which is characterized in that the light transmission rate T ＞ of the ito thin film layer 90%, electricalresistivityρ ＜ 4 × 10^-4Ω cm, refractive index n are 2.1~2.5.

3. a kind of preparation method of crystal silicon flexible battery as claimed in claim 1 or 2, comprises the following steps：

（1）Chemical etching：Chemical etching is carried out on the monosilicon, etches cylindrical silicon array structure, obtains cylindrical silicon battle array Array structure layer；

（2）Diffusion：PN junction is prepared using diffusion technique on cylindrical silicon array structure layer, obtains PN junction layer；

（3）Prepare SiNx passivation layers：SiNx passivation layers are prepared using pecvd process on PN junction layer；

（4）Plate ito thin film layer：Ito thin film is plated using pecvd process on SiNx passivation layers, obtains ito thin film layer；

（5）Etch the silicon back side：In step（1）The monocrystalline silicon back side of reservation, which performs etching, cuts thin, obtains monocrystal silicon substrate layer；

（6）Plate aluminum back electrode：In the back side silk-screen printing aluminium paste of monocrystal silicon substrate layer, after sintering, aluminum back electrode layer is obtained；

（7）Encapsulation：By step（1）~（6）The battery component of each structure sheaf composition prepared respectively is packaged, and it is soft to obtain crystal silicon Property battery；

The step（2）In, the diffusion technique includes following process：First in O₂And N₂In atmosphere at 600 DEG C~800 DEG C oxygen Change 3min~5min, then lead to POCl₃、O₂And N₂, 3min~5min is spread in the case where diffusion temperature is 800 DEG C~825 DEG C, then is risen High-temperature is to 810 DEG C~835 DEG C, in POCl₃、O₂And N₂3min~5min is spread in atmosphere deeply, further pushes away deep PN junction；

The step（3）In, the condition of the pecvd process is：Vacuum pressure be 180Pa~230Pa, coating temperature 430 DEG C~450 DEG C, it is passed through SiH₄And NH₃, SiH₄With NH₃Gas flow ratio for 4200: 500, radio-frequency power for 3500W~ 4000W。

4. the preparation method of crystal silicon flexible battery according to claim 3, which is characterized in that the step（6）In, it is described Sintering process is as follows：First aluminium paste is dried, drying temperature is 100 DEG C~200 DEG C, and drying time is 10 min~20min, then 30min~60min is sintered at 400 DEG C~450 DEG C, 10min~25min is sintered at 600 DEG C~900 DEG C, forms ohm Contact.

5. the preparation method of crystal silicon flexible battery according to claim 3, which is characterized in that the step（7）In, it is described The material of encapsulation is dimethyl silicone polymer.