CN103746008A - Antireflection layer for solar cell and preparing process of antireflection layer - Google Patents

Abstract

The invention discloses an antireflection layer for a solar cell and a preparing process of the antireflection layer. The antireflection layer is characterized by being formed by Gd2O3. The preparing process comprises the steps of firstly depositing a Gd2O3 antireflection layer at one side of an N-type diffusion layer of a P-type silicon with an organic chemical vapor deposition method, then performing annealing treatment to form an SiO2 buffer layer between the antireflection layer and the N-type diffusion layer, thus finishing the preparing of the antireflection layer. The antireflection layer has the advantages of being low in Si lattice miss-matching ratio, large in forbidden bandwidth, high in refractive index, good in stability and the like.

Description

A kind of anti-reflection layer for solar cell and its preparation process

technical field

The present invention belongs to the field of semiconductors, in particular to the application field of optoelectronic materials, and in particular to an anti-reflection layer and its preparation process.

Background technique

The anti-reflection layer is very important for solar cells. It can increase the light absorption of solar cells by reducing the reflected light of solar cells, increase the short-circuit current of solar cells, and thus improve the photoelectric conversion efficiency of solar cells. However, traditional anti-reflection materials have insurmountable defects, such as SiO ₂ , MgF ₂ and other anti-reflection materials whose refractive index is too low, and the band gap of TiO ₂ is too narrow. Seeking a high-performance anti-reflection material has become the current photovoltaic industry research hotspot.

Contents of the invention

The object of the present invention is to provide a kind of anti-reflection layer of solar cell, and this anti-reflection layer adopts new anti-reflection material, and this anti-reflection material has low lattice mismatch ratio with Si, wide band gap, high refractive index, stable It can be used to replace traditional anti-reflection materials such as SiO ₂ , MgF _{2 ,} TiO _{2 ,} etc., and the invention also provides a preparation process for the anti-reflection layer.

The technical solution adopted to achieve the above object of the present invention is: an anti-reflection layer for solar cells, characterized in that the anti-reflection layer is made of gadolinium oxide (Gd ₂ O ₃ ).

The anti-reflection layer of the invention can be applied to the anti-reflection layer of monocrystalline silicon and polycrystalline silicon solar cells.

The preparation process of the above-mentioned antireflection layer for solar cells is characterized in that in the production of P-type crystalline silicon, after the P-type crystalline silicon has completed the HF acid pickling process, organic chemical vapor deposition (MOCVD) is used on the N-type diffusion layer An anti-reflection layer of gadolinium oxide is deposited on it, and annealing is performed to form a SiO ₂ buffer layer between the anti-reflection layer and the N-type diffusion layer to complete the preparation of the anti-reflection layer.

The optimum thickness of the deposited gadolinium oxide antireflection layer is 70-140nm.

In the MOCVD deposition method of gadolinium oxide, the precursor is an organometallic compound of gadolinium, the reaction temperature of the chamber is 300-700°C, the deposition time is 15-30min, the evaporation temperature is 100-250°C, and the pressure is 2-10mbar. The carrier gas is a mixed gas of Ar and _O2 .

The annealing process to form the _SiO2 buffer layer is as follows: put the battery sheet deposited with the gadolinium oxide anti-reflection layer into an annealing furnace with an inert gas or an oxidizing gas, control the annealing temperature to 300-800°C, and the annealing time For 0.5 to 4 hours, a thin SiO ₂ layer (buffer layer) of about 1 nm is formed between the anti-reflection layer and the N-type diffusion layer.

The inert gas or oxidizing gas is any one of Ar, N ₂ , N ₂ O or H ₂ .

In the above-mentioned technical scheme of the present invention, in the production process of P-type crystalline silicon, after cleaning the P-type crystalline silicon substrate, texturizing, diffusing phosphorus, edge etching, and HF pickling agent washing, organic chemical vapor deposition is used to Method (MOCVD) Deposit gadolinium oxide anti-reflection layer on the crystalline silicon wafer, and perform annealing treatment, form a SiO ₂ buffer layer between the anti-reflection layer and the N-type diffusion layer, complete the preparation of the anti-reflection layer, and then perform electrode and electric field The fabrication of crystalline silicon cells is completed.

Gd ₂ O ₃ has the same cubic phase structure as Si at room temperature, and its dielectric constant is high, K(Gd ₂ O ₃ ) =14～22, and it has a very close lattice matching constant with Si (a(Gd ₂ O ₃ )=10.812A; 2a(Si)=10.862A), the lattice mismatch rate is very low, high-quality films can be grown on Si, and Gd ₂ O ₃ has high thermodynamic stability (>1000℃ ), large bandgap width (5.9ev) and high refractive index (1.9), it is an ideal material for preparing anti-reflection layer.

The present invention uses gadolinium oxide as the anti-reflection material for the anti-reflection layer of the solar cell. In the manufacture of the solar cell, the gadolinium oxide anti-reflection layer is first deposited after being washed with P-type silicon HF pickling agent, and then the anti-reflection layer is deposited in an inert gas protection environment. Or annealing treatment is carried out under the protection environment of oxidizing gas, and a SiO ₂ buffer layer is formed between the anti-reflection layer and the crystalline silicon cell. The gadolinium oxide anti-reflection layer is prepared by MOCVD. The obtained anti-reflection layer has good lattice matching with the crystalline silicon substrate, low defect density, high refractive index, good thermal stability, and large forbidden band width, which ensures the anti-reflection of the battery Effect.

Description of drawings

Fig. 1 is the structural representation of the P-type crystalline silicon solar cell that contains gadolinium oxide anti-reflection layer;

Fig. 2 is a flow chart of the preparation of a P-type crystalline silicon solar cell containing a gadolinium oxide anti-reflection layer.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings and specific implementation examples, but the described embodiments should not be interpreted in a limiting manner.

The anti-reflection layer of the solar cell and its preparation process of the present invention is to deposit the anti-reflection layer of gadolinium oxide by organic chemical vapor deposition (MOCVD) after the HF pickling agent process is completed on the P-type crystalline silicon. In the MOCVD deposition method of gadolinium oxide, the precursor is an organometallic compound of gadolinium, the reaction temperature of the chamber is 300-700°C, the deposition time is 15-30min, the evaporation temperature is 100-250°C, and the pressure is 2-10mbar. The gas is a mixed gas of Ar and _O2 . Then perform an annealing treatment to form a SiO ₂ buffer layer to complete the preparation of the anti-reflection layer. The annealing process to form the _SiO2 buffer layer is as follows: put the battery sheet deposited with the gadolinia-alumina anti-reflection layer into an annealing furnace with an inert gas or an oxidizing gas, control the annealing temperature to 300-800°C, and the annealing time For 0.5 to 4 hours, a SiO ₂ buffer layer of about 1 nm is formed between the anti-reflection layer and the N-type diffusion layer.

Specific examples are as follows:

It can be seen from the flow chart of the preparation of a P-type crystalline silicon solar cell containing a gadolinium oxide anti-reflection layer given in Figure 2 that the process for preparing a P-type crystalline silicon solar cell is as follows:

a. Use HF and HC1 to clean and texture the P-type crystalline silicon substrate in order to remove the mechanical damage layer, oil stains and metal impurities, and at the same time form an uneven texture on the surface to increase the surface area and increase light absorption; then P Type crystalline silicon substrate is placed in the diffusion chamber, and a phosphorus source is introduced to diffuse phosphorus into the surface of P-type crystalline silicon to form an N layer, that is, a PN junction; then use a mixed liquid of HNO ₃ and HF to perform peripheral etching to remove The N layer deposited on the edge in order to insulate the battery sheet from the outside world; then the phosphorous silicon glass is removed, that is, the silicon dioxide and other substances formed during the diffusion process are washed away with HF. The above is the conventional process in the solar cell manufacturing process, which will not be repeated here.

b. After completing the above steps, quickly put the P-type crystalline silicon cell into the MOCVD reaction chamber, and deposit a gadolinium oxide anti-reflection layer on the N-type diffusion layer on the side of the N-type diffusion layer by MOCVD, and its thickness is controlled at In the range of 70-140nm, in the preparation process of gadolinium oxide anti-reflection layer, the precursor is acetylacetonate Gd(acac) ₃ , the reaction temperature of the chamber is 300-700°C, the deposition time is 15-30min, and the evaporation temperature is 100～250℃, the pressure is 2～10mbar, the carrier gas is the mixed gas of Ar and _O2 .

c. After the gadolinium oxide anti-reflection layer is deposited, annealing is performed to form a SiO ₂ buffer layer between the anti-reflection layer and the N-type diffusion layer. Put the cell into an annealing furnace with any one of Ar, N ₂ , N ₂ O or H ₂ , set the annealing temperature in the range of 300-800°C, and control the annealing time in the range of 0.5-4 hours , so that a thin SiO ₂ layer (SiO ₂ buffer layer) of about 1nm is formed between the anti-reflection layer and the N-type diffusion layer. So far, the preparation of the anti-reflection layer is completed.

d. Prepare an aluminum back electric field and a metal grid-shaped back electrode on the backlight side of the battery, and prepare a metal grid wire front electrode on the light-facing side (including the anti-reflection layer side). After drying and sintering, a complete battery with A crystalline silicon solar cell with gadolinium oxide anti-reflection layer.

It can be seen from the structural diagram of a P-type crystalline silicon solar cell with a gadolinium oxide anti-reflection layer shown in Figure 1 that phosphorus is diffused on a P-type crystalline silicon substrate 1 to form an N diffusion layer 2, and then diffused on the N A layer of gadolinium oxide anti-reflection layer 3 is deposited on the surface of layer 2 by MOCVD method. The gadolinium oxide anti-reflection layer 3 is annealed to form a SiO ₂ buffer layer 4. The SiO ₂ buffer layer 4 is located between the anti-reflection layer 3 and the N-type Between the diffusion layers 2, finally screen-print the aluminum back electric field 5 and the metal grid line back electrode 6 on the P-type substrate 1, and screen-print the metal grid line front electrode 7 on the anti-reflection layer 3, thereby making a A crystalline silicon solar cell with an anti-reflection layer of gadolinium oxide.

The organic chemical vapor deposition method (MOCVD) is the common knowledge of those skilled in the art and will not be repeated here.

The above is an illustration but not a limitation of the present invention, and other implementations based on the idea of the present invention are within the protection scope of the present invention.

Claims (7)

1. An antireflection layer for a solar cell, characterized in that the antireflection layer is made of gadolinium oxide. 2. The anti-reflection layer for solar cells according to claim 1, characterized in that the anti-reflection layer is applied in the anti-reflection process of monocrystalline silicon and polycrystalline silicon solar cells. 3. A process for preparing the solar cell anti-reflection layer described in claim 1 or 2 is characterized in that in the making of P-type crystalline silicon, after the P-type crystalline silicon completes the HF pickling process, organic chemical vapor phase is used to The deposition method deposits the gadolinium oxide anti-reflection layer on the N-type diffusion layer and performs annealing treatment to form a _SiO2 buffer layer between the anti-reflection layer and the N-type diffusion layer to complete the preparation of the anti-reflection layer. 4. The preparation process of the anti-reflection layer for solar cells according to claim 3, characterized in that the thickness of the deposited gadolinium oxide anti-reflection layer is 70-140 nm. 5. according to the preparation technology of solar cell antireflection layer according to claim 3, it is characterized in that in the organic chemical vapor deposition method of gadolinium oxide, the precursor is the organometallic compound of gadolinium, and the reaction temperature of chamber is 300～ 700°C, the deposition time is 15-30min, the evaporation temperature is 100-250°C, the pressure is 2-10mbar, and the carrier gas is a mixed gas of Ar and _O2 . 6. according to the preparation technology of solar cell anti-reflection layer according to claim 3, it is characterized in that described annealing treatment forms SiO ₂ The technique of buffer layer is: the cell sheet that is deposited with gadolinium oxide anti-reflection layer is put into In the annealing furnace with inert gas or oxidizing gas, control the annealing temperature to 300-800°C and the annealing time to 0.5-4 hours, and form a SiO ₂ buffer layer of about 1nm between the anti-reflection layer and the N-type diffusion layer. 7. The process for preparing an anti-reflection layer for solar cells according to claim 6, wherein the inert gas or oxidizing gas is any one of Ar, N ₂ , N ₂ O or H ₂ .

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