CN106328736B - A kind of anti-LID black silicon solars high-efficiency battery and its production method - Google Patents

Abstract

The invention relates to an anti-LID black silicon solar high-efficiency cell and a production method thereof, comprising positive and negative electrodes, an aluminum back field, a P-type silicon wafer substrate, and a PN junction sequentially located on the P-type silicon wafer substrate, _SiO2 oxidation film, SiNx thin film, the thickness of the PN junction is uniform, and the SiNx thin film is coated on the surface of the _SiO2 oxide film; through the production of high light-trapping nano-columns, the first diffusion, the removal of edge junctions and phosphosilicate glass layers, and the second Secondary diffusion, SiNx surface passivation and anti-reflection film deposition, preparation of battery negative electrode, positive electrode and aluminum back field, complete the preparation of anti-LID black silicon solar cells. The invention enhances the absorption of light energy, improves the photoelectric conversion efficiency, reduces the leakage phenomenon of the battery, and has anti-LID and PID effects.

Description

A kind of anti-LID black silicon solar energy efficient battery and production method thereof

technical field

The invention relates to the field of solar cells, and specifically discloses a high-efficiency anti-LID black silicon solar cell and a production method thereof.

Background technique

Silicon is one of the most abundant elements in the world, and it is widely used in important fields such as photoelectric detection, optical communication, and microelectronic equipment. However, due to the nature of crystalline silicon, the surface of crystalline silicon has a high reflection of visible-infrared light, which greatly limits the key technical indicators such as sensitivity, usable wavelength range and conversion efficiency of silicon-based optoelectronic devices. In recent years, a kind of microstructured silicon called black silicon has attracted great attention. Due to its extremely high absorption of visible-infrared light, black silicon can be widely used in biology, infrared detection, solar cells, Pharmacy, microelectronics, agriculture and safety testing, etc. Conventional crystalline silicon solar cells are all based on p-type boron-doped silicon crystals, but this kind of cell has light attenuation phenomenon, which has become an important bottleneck restricting the development of high-efficiency solar cells. At present, the nature and mechanism of light attenuation phenomenon is not completely clear, it is one of the research hotspots in the direction of crystalline silicon solar cell materials and devices in the world. The problem of light attenuation can be solved by suppressing the formation of boron-oxygen complexes caused by defects in light attenuation. The method of suppressing boron-oxygen complexes includes ① reducing oxygen content ② reducing boron concentration ③ p-type gallium-doped silicon crystal (gallium replaces boron) ④ n-type Silicon crystal (without boron) ⑤High temperature heat treatment ⑥Similar doped (germanium, tin and carbon) silicon crystal.

At present, there are various methods for preparing black silicon, and the two most industrialized methods are dry texturing RIE (Reactive Ion Etching) and wet texturing MCCE (Met Aluminum Catalyzed Chemic Aluminum Etching). Using RIE or MCCE method to prepare black silicon nano light-trapping eye structure can significantly improve the spectral absorption in the visible-infrared band, but due to the increase of the surface area and the introduction of defects during the preparation of black silicon, it has a high surface recombination rate. And the lower minority carrier lifetime leads to the decrease of open circuit voltage and the increase of leakage, and the photoelectric conversion efficiency of solar cells has not been significantly improved. The black silicon nano-light trapping hole structure makes the formed PN junction uneven in depth, and most of the boron and oxygen at the shallow junction of the PN junction are in a metastable state, and it is easy to form a boron-oxygen complex, resulting in more serious light attenuation (LID). At the same time, the shallow junction of the PN junction is easy to burn through, resulting in more serious leakage of the solar cell.

Contents of the invention

The object of the present invention is to provide a high-efficiency anti-LID black silicon solar cell with anti-LID and PID effects and a production method thereof that enhances light energy absorption, improves photoelectric conversion efficiency, and reduces battery leakage to solve the above problems.

The technical scheme adopted in the present invention is as follows:

An anti-LID black silicon solar high-efficiency cell, including positive and negative electrodes and an aluminum back field, also includes a P-type silicon substrate and a PN junction, _SiO2 oxide film, and SiNx film that are sequentially located on the P-type silicon substrate, The thickness of the PN junction is uniform, and the SiNx film is coated on the surface of the _SiO2 oxide film

Further, one end of the P-type silicon wafer substrate is flat, and the other end is a light-trapping structure, and the end face of the light-trapping structure is a PN junction; the outside of the PN junction and the outer layer of the P-type silicon wafer substrate light-trapping structure It is a _SiO2 oxide film; one end of the SiNx film is flat, and the other end is matched with the end of the light-trapping structure of the P-type silicon wafer substrate.

Further, the purity of the P-type silicon wafer substrate is greater than 99.9999%.

Further, the depth of the PN junction is 0.1-10 μm.

Further, the thickness of the SiNx film is 50-150 nm.

The production method of above-mentioned a kind of anti-LID black silicon solar energy high-efficiency cell, comprises the steps:

(1) Fabrication of high-light-trapping nanocolumns: P-type silicon wafers are processed by RIE method or MCCE method to prepare high-light-trapping nanocolumns;

(2) For the first diffusion, the silicon wafer is placed in a diffusion furnace, and the diffusion is carried out by introducing a phosphorus source process under the atmosphere of protective gas N ₂ and O ₂ ;

(3) Remove the edge junction and phosphosilicate glass layer;

(4) The second diffusion, in the diffusion furnace, using _O2 as the diffusion source, diffusion is carried out under the protective gas _N2 atmosphere;

(5) Use PEVCD equipment to perform SiNx surface passivation and anti-reflection film deposition on silicon wafers;

(6) Prepare the negative electrode, positive electrode and aluminum back field of the battery, and complete the preparation of the anti-LID black silicon solar cell.

Further, the gas diffusion temperature in the step (2) is 810-860°C.

Further, in the step (3), the edge junction and the phosphosilicate glass layer are removed by a wet etching process, followed by a mixed acid etching tank, back polishing, diluted hydrofluoric acid, and deionized water cleaning treatment, wherein the acid The concentration of lye and lye remain unchanged.

Further, the gas diffusion temperature in the step (4) is 600-800°C.

In summary, owing to adopting above-mentioned technical scheme, the beneficial effect of the present invention is:

1. Use the RIE method or MCCE method to form a black silicon nano-light trapping eye structure. Due to the unique anti-reflection effect of the ultra-low nano-anti-reflection structure array, the absorption of light energy is increased, which is conducive to improving the conversion efficiency of nano-pillar cells;

2. Through two diffusions, the first is due to the black silicon nano-light trapping hole structure, which promotes the redistribution of phosphorus to form a uniform PN junction surface through re-diffusion, effectively preventing the light attenuation caused by the shallow PN junction in the concave part of the high trapping light structure, It has an anti-LID effect; secondly, it improves the ohmic contact characteristics of the nano-column and the electrode, improves the contact problem between the black silicon nano-hole structure and the electrode, and reduces the leakage phenomenon of the solar cell; thirdly, the surface of the silicon wafer is obtained. The impurity concentration is low, the surface recombination is small, and the open circuit voltage of the solar cell is increased, thereby significantly improving the photoelectric conversion efficiency of the solar cell; fourth, a silicon dioxide passivation film is formed on the surface of the phosphorus diffusion layer, which has an anti-PID effect.

Description of drawings

Fig. 1 is a structural schematic diagram of the present invention.

Marks in the figure: 1. Positive electrode; 2. Negative electrode; 3. Aluminum back field; 4. P-type silicon wafer substrate; 5. PN junction; 6. SiO ₂ oxide film; 7. SiNx film.

Detailed ways

All features disclosed in this specification, or steps in all methods or processes disclosed, may be combined in any manner, except for mutually exclusive features and/or steps.

Any feature disclosed in this specification (including any appended claims, abstract and drawings), unless expressly stated otherwise, may be replaced by alternative features which are equivalent or serve a similar purpose. That is, unless expressly stated otherwise, each feature is one example only of a series of equivalent or similar features.

As shown in Figure 1, a kind of anti-LID black silicon solar energy high-efficiency battery comprises positive and negative electrodes 1, 2 and aluminum back field 3, also includes P-type silicon wafer substrate 4 and is positioned on P-type silicon wafer substrate 4 successively PN junction 5, SiO ₂ oxide film 6, SiNx thin film 7, one end of the P-type silicon chip substrate 4 is flat, the other end is a light trapping structure, and the end face of the light trapping structure is a PN junction 5, and the surface of the PN junction 5 Uniform, with a depth of 0.1 to 1.0 microns; the outside of the PN junction 5 and the outer layer of the light-trapping structure end of the P-type silicon wafer substrate 4 is a _SiO2 oxide film 6, which has an anti-LID effect; one end of the SiNx film 7 is flat, and the other One end is matched with the light-trapping structure end of the P-type silicon wafer substrate 4 . The thickness of the SiNx thin film 7 is 50-150 nm.

The production method of above-mentioned a kind of anti-LID black silicon solar energy high-efficiency cell, comprises the steps:

(1) Fabrication of high-light-trapping nanocolumns, the P-type silicon wafer substrate 4 is a solar-grade silicon substrate with a purity greater than 99.9999%, and is P-type doped. The MCCE (Metal Catalyzed Chemical Corrosion) method to prepare high light-trapping nanopillars is to add nanometer metal particle catalysts during corrosion, after mixed acid corrosion treatment, alkali pore expansion treatment, hydrofluoric acid treatment, and deionized water cleaning process, during which the acid solution Concentration and lye concentration remain unchanged. RIE (plasma texturing) method to prepare high-light-trapping nanocolumns is to pass the gas required for plasma texturing in a vacuum environment, and then apply a negative bias voltage on the silicon wafer, and immerse the silicon wafer directly in the plasma. Light-trapping nanostructures are formed on the surface of the wafer, and finally the light-trapping nanostructures are de-damaged; the average reflectance of the silicon wafers after texturing is 5% to 15%.

(2) The first diffusion, the first phosphorus diffusion treatment is carried out on the above-mentioned silicon wafers. The phosphorus diffusion treatment is a traditional diffusion process, including pre-deposition and re-advancing process. The phosphorus diffusion uses POCl ₃ as the phosphorus diffusion source. Diffusion is carried out by introducing phosphorus source technology under gaseous N ₂ and O ₂ atmosphere. The gas diffusion temperature is 810℃～860℃. The flux ranges of each gas are as follows: small N ₂ : 0-1.8 slm; N ₂ : 2-20 slm; O ₂ : 0-1.1 slm. The sheet resistance after diffusion is 50-150 ohms, and the depth of the PN junction 5 is 0.1-1.0 microns.

(3) Remove the edge junction and phospho-silicate glass layer; use the wet etching process to go through the mixed acid etching tank to remove the edge of the silicon wafer, remove the edge short circuit part that may be caused during the diffusion process, and at the same time clean the back of the silicon wafer Polishing followed by treatment with dilute hydrofluoric acid removes the layer of phosphosilicate glass produced by the diffusion. Finally rinse with deionized water. During this period, the concentration of acid solution and lye solution remained unchanged.

(4) The second diffusion, in order to solve the inhomogeneous PN junction phenomenon that the groove depth of the nanopillar prepared by RIE method or MCCE method in step (1) is large, the junction of the convex part is deep during the diffusion process, and the junction of the groove is shallow , a second diffusion is required. Secondary diffusion is the process of redistribution of phosphorus and generation of oxide layer, and oxygen diffusion is carried out on the diffused side of the silicon wafer. Using _O2 as a diffusion source, diffusion is carried out under the protective gas _N2 atmosphere, and a silicon dioxide oxide layer passivation film is formed on the surface of the phosphorus diffusion layer. The secondary diffusion temperature is 650°C to 800°C, which is lower than the primary diffusion temperature.

(5) SiNx surface passivation and anti-reflection film deposition are carried out on silicon wafers. The SiNx surface passivation and anti-reflection film deposition on silicon wafers is to use PEVCD equipment to deposit a layer of SiNx film 7 on the diffusion surface of silicon wafers. The thickness is 50-150nm. After completion of PEVCD, the reflectivity is 0-15%.

(6) Prepare the negative electrode, positive electrode and aluminum back field of the battery, and complete the preparation of the anti-LID black silicon solar cell.

The above-mentioned embodiments are only to illustrate the technical concept and characteristics of the present invention, and its purpose is to allow those of ordinary skill in the art to understand the content of the present invention and implement it accordingly, and cannot limit the protection scope of the present invention; Equivalent changes or modifications made to the essence of the present invention shall fall within the protection scope of the present invention.

Claims (8)

1. a kind of anti-LID black silicon solars high-efficiency battery, including positive and negative electrode and Al-BSF, further include P-type wafer substrate and according to Secondary PN junction, SiO on P-type wafer substrate₂Oxide-film, SiNx films, the PN junction thickness is uniform, the SiNx films bag Overlay on SiO₂Aoxidize film surface；

Described P-type wafer substrate one end is smooth, and the other end is in light trapping structure, is PN junction in its light trapping structure end end face；The PN Knot outside, P-type wafer substrate light trapping structure end outer layer are SiO₂Oxide-film；Described SiNx films one end is smooth, the other end and institute State P-type wafer substrate light trapping structure end and form identical setting；

It is characterized in that：The light trapping structure indention shape, and the zigzag fashion is relatively distant from the P-type wafer substrate Smooth one end is the tooth tip portion of the zigzag fashion, and the relatively close P-type wafer substrate of the zigzag fashion is smooth One end be the zigzag fashion root portion, the SiO₂Oxide-film is arranged between the PN junction and the SiNx films, and The SiO₂Oxide-film and the PN junction, the SiO₂Oxide-film connects with the SiNx films in the position close to the tooth tip portion Touch, the SiO₂Oxide-film and the PN junction are rounded contact, the SiO₂Oxide-film is contacted with the SiNx films for obtuse angle.

A kind of 2. anti-LID black silicon solars high-efficiency battery according to claim 1, it is characterised in that：The P-type wafer lining Bottom purity is more than 99.9999%.

A kind of 3. anti-LID black silicon solars high-efficiency battery according to claim 1, it is characterised in that：The PN junction depth is 0.1~10μm。

A kind of 4. anti-LID black silicon solars high-efficiency battery according to claim 1, it is characterised in that：The SiNx films Thickness is 50 ~ 150nm.

A kind of 5. production method of anti-LID black silicon solars high-efficiency battery as claimed in claim 1, it is characterised in that：Including Following steps：

（1）The making of high light trapping nano-pillar, carries out P-type wafer RIE methods or the processing of MCCE methods prepares high light trapping nano-pillar；

（2）Spread, silicon chip is placed in diffusion furnace, in protective gas N for the first time₂、O₂Used under atmosphere and be passed through the progress of phosphorus source technique Diffusion；

（3）Remove flash trimming knot and phosphorosilicate glass layer；

（4）Second of diffusion, in diffusion furnace, utilizes O₂As diffusion source, in protective gas N₂It is diffused under atmosphere；

（5）SiNx surface passivations and anti-reflection thin film deposition are carried out to silicon chip using PEVCD equipment；

（6）Battery negative electrodes, positive electrode and Al-BSF are prepared, anti-LID black silicon solar cells is completed and prepares.

A kind of 6. production method of anti-LID black silicon solars high-efficiency battery according to claim 5, it is characterised in that：Institute State step（2）Middle gas diffusion temperature is 810 ~ 860 DEG C.

A kind of 7. production method of anti-LID black silicon solars high-efficiency battery according to claim 5, it is characterised in that：Institute State step（3）It is middle that flash trimming knot and phosphorosilicate glass layer are gone using wet-etching technology, successively by nitration mixture etching groove, polished backside, Diluted hydrofluoric acid, deionized water cleaning treatment, wherein acid strength and concentration of lye remain unchanged.

A kind of 8. production method of anti-LID black silicon solars high-efficiency battery according to claim 5, it is characterised in that：Institute State step（4）Middle gas diffusion temperature is 600 ~ 800 DEG C.