CN106169518A - A kind of laser pulse method carrying on the back passivation solaode - Google Patents

Abstract

The invention discloses a laser pulse method for back passivation solar cells. It includes the following steps: A. Carry out texturing treatment on monocrystalline silicon wafers to form pyramid textured surfaces; B. Diffusion to prepare PN junctions; C. Polishing to remove edge junctions and surface defects; D. Form blunt front and back sides by ALD and PECVD chemical film layer; E, laser slotting is carried out on the back surface, the slotting adopts pulse mode as multi-pulse, and the number of pulses is 2-5; F, screen printing forms positive electrode, back electrode and back field; G, sintering makes metal Makes good ohmic contact with silicon. Its advantages are: the damage to the silicon substrate and the film layer is reduced, the requirements for the smoothness of the film layer are relaxed when the laser is grooved, and the smoothness of the grooved part is better, thereby reducing the damage to the back film layer and the silicon substrate. damage and enhance the passivation effect; the flatness of the laser grooved part is better, so that the silicon substrate can form a good ohmic contact with the aluminum back field, thereby improving the conversion efficiency of the solar cell.

Description

A laser pulse method for back-passivated solar cells

technical field

The invention relates to a laser pulse method for back-passivated solar cells, belonging to the technical field of solar cell manufacture.

Background technique

Since the Al2O3 thin film and the SiN thin film are both insulating layers and cannot conduct electricity, the main function of the laser is to cut the back film layer to expose the silicon substrate. After the back electric field printing and sintering is completed, the silicon substrate can form a good ohmic contact with the aluminum back field. In this way, the laser output energy has an important influence on the passivation effect of aluminum oxide. The laser output energy will increase the corrosion depth and the thermal damage will directly affect the passivation effect of the aluminum oxide film layer, which will reduce the open circuit voltage and the laser output energy. If it is small, the etching depth will be insufficient, and the silicon nitride and aluminum oxide film layers on the back cannot be completely penetrated, resulting in poor contact between the silicon substrate and the aluminum back field, which will greatly increase the series resistance and reduce the filling.

At present, the common laser pulse method is mostly single pulse. On the one hand, the output energy of this pulse method is relatively large, it is difficult to control, the stability is poor, and it is easy to cause damage to the film layer and silicon substrate; on the other hand, the current polishing process is suitable for PERC. Acid polishing is often used for mass production of batteries, but this polishing method corresponds to poor flatness of the back coating layer. The poor morphology of the grooved parts by single pulse laser is mainly reflected in the flatness, which makes the silicon substrate and the aluminum back field poor contact.

Contents of the invention

The technical problem to be solved by the present invention is to provide a laser pulse method for back passivation of solar cells that can reduce damage to the back film and silicon substrate, enhance the passivation effect, and improve the conversion efficiency of PERC cells.

In order to solve the above-mentioned technical problems, the laser pulse method of the back passivation solar cell of the present invention comprises the following steps:

A. Carry out texturing treatment to the monocrystalline silicon wafer to form a pyramid textured surface;

B. Diffusion to prepare PN junction;

C. Polishing to remove edge knots and surface defects to make the back surface smooth;

D. A passivation film layer is formed on the front and back sides by ALD and PECVD;

E. Laser equipment is used for laser slotting on the back surface, and the slotting adopts pulse mode as multi-pulse, and the number of pulses is 2-5;

F. Screen printing to form positive electrode, back electrode and back field;

G. Sintering makes good ohmic contact between metal and silicon.

After the step G is completed, test the electrical performance of the battery.

In the step E, the output power is 10-40W, the frequency is 400-1000KHz, the frequency corresponds to the number of pulses, and the product of the frequency and the number of pulses is less than 2000.

The passivation film is aluminum oxide, silicon nitride or silicon oxide thin film or a laminated film of at least two materials, and the thickness of the film layer is 50-300nm.

The laser device is a picosecond, subsecond or nanosecond laser.

The advantages of the present invention are:

Since the slotting adopts multi-pulse pulse mode, especially the parameter range of the laser is set, so that under the same conditions, the total energy output by using multi-pulse is small, which reduces the damage to the silicon substrate and the film layer, and at the same time The increase in the number of pulses relaxes the requirements for the smoothness of the film layer during laser grooving, making the smoothness of the grooving part better, thereby reducing the damage to the back film layer and silicon substrate, and enhancing the passivation effect; at the same time, laser grooving The flatness of the part is better, so that the silicon substrate can form a good ohmic contact with the aluminum back field, thereby improving the conversion efficiency of the solar cell.

detailed description

The laser pulse method of the back passivated solar cell of the present invention will be further described in detail below in conjunction with specific embodiments.

The laser pulse method of the back passivation solar cell of the present invention comprises the following steps:

A. Carry out texturing treatment to the monocrystalline silicon wafer to form a pyramid textured surface;

B. Diffusion to prepare PN junction;

C. Polishing to remove edge knots and surface defects to make the back surface smooth;

D. A passivation film is formed on the front and back by ALD and PECVD; the passivation film is aluminum oxide, silicon nitride or silicon oxide film or a laminated film of at least two of them, and the film thickness is 50-300nm;

E. Use laser equipment to carry out laser slotting on the back surface. The slotting method is multi-pulse, and the number of pulses is 2-5; the output power is 10-40W, and the frequency is 400-1000KHz. The frequency corresponds to the number of pulses. The product of the frequency and the number of pulses is less than 2000; the said laser device is a picosecond, subsecond or nanosecond laser.

F. Screen printing to form positive electrode, back electrode and back field;

G. Sintering makes good ohmic contact between metal and silicon.

H, to test the electrical performance of the battery.

Its comparative examples are as follows:

Comparative example one:

A. Carry out texturing treatment to the monocrystalline silicon wafer to form a pyramid textured surface;

B. Diffusion to prepare PN junction;

C. Polishing to remove edge knots and surface defects to make the back surface smooth;

D. A passivation film is formed on the front and back surfaces by ALD and PECVD. The front is a silicon nitride film with a thickness of 80nm, and the back is a laminated film of aluminum oxide and silicon nitride with a thickness of 130nm;

E. Use a picosecond laser to make laser grooves on the back surface. The pulse mode for grooves is single pulse, the groove frequency is 625KHz, and the output power is 12W.

F. Screen printing to form positive electrode, back electrode and back field;

G. Sintering makes good ohmic contact between metal and silicon;

H. Test the electrical performance of the battery.

Comparative example two:

The laser pulse method of the back passivation solar cell of the present embodiment comprises the following steps:

A. Carry out texturing treatment to the monocrystalline silicon wafer to form a pyramid textured surface;

B. Diffusion to prepare PN junction;

C. Polishing to remove edge knots and surface defects to make the back surface smooth;

D. A passivation film is formed on the front and back by ALD and PECVD; the front is a silicon nitride film with a thickness of 80nm, and the back is a laminated film of aluminum oxide and silicon nitride with a thickness of 130nm;

E. Laser slotting is performed on the back surface of the picosecond laser, the slotting adopts a pulse mode of double pulse, the slotting frequency is 625KHz, and the output power is 12W;

F. Screen printing to form positive electrode, back electrode and back field;

G. Sintering makes good ohmic contact between metal and silicon.

F, to test the electrical performance of the battery.

Comparative example three:

A. Carry out texturing treatment to the monocrystalline silicon wafer to form a pyramid textured surface;

B. Diffusion to prepare PN junction;

C. Polishing to remove edge knots and surface defects to make the back surface smooth;

D. A passivation film is formed on the front and back surfaces by ALD and PECVD. The front is a silicon nitride film with a thickness of 80nm, and the back is a laminated film of aluminum oxide and silicon nitride with a thickness of 130nm;

E. Use a picosecond laser to make laser grooves on the back surface. The groove adopts three pulses, the groove frequency is 625KHz, and the output power is 12W.

F. Screen printing to form positive electrode, back electrode and back field;

G. Sintering makes good ohmic contact between metal and silicon;

H. Test the electrical performance of the battery.

The electrical properties of the PERC battery prepared according to the above method are shown in Table 1. It can be seen that the efficiency of multi-pulse is 0.2-0.4% higher than that of single-pulse, mainly due to the improvement of opening pressure and filling. With the increase of the number of pulses, the opening Pressure lift is reduced.

pulse mode Eta Uoc Isc FF Rs. Rsh monopulse 20.92 0.652 9.711 79.56 0.0020 170.22 double pulse 21.26 0.654 9.725 80.55 0.0018 250.12 triple pulse 21.26 0.655 9.757 80.14 0.0019 324.81

Claims (5)

1. carry on the back a laser pulse method for passivation solaode, comprise the following steps:

A, monocrystalline silicon piece is carried out making herbs into wool process, form pyramid matte；

B, diffusion are for PN junction；

Flash trimming knot and surface defect are gone in C, polishing, make back surface smooth；

D, made by ALD, PECVD the positive back side formed passivation film；

E, using laser equipment to carry out lbg at back surface, fluting uses pulse mode to be multiple-pulse, and umber of pulse is 2-5；

F, silk screen printing form anelectrode, back electrode and back surface field；

G, sintering make to form good Ohmic contact between metal and silicon.

2. according to the laser pulse method of the back of the body passivation solaode described in claim 1, it is characterised in that: described step G Carry out testing the electrical property of battery after completing.

3. according to the laser pulse method of the back of the body passivation solaode described in claim 1 or 2, it is characterised in that: described step In rapid E, output is 10-40W, and frequency is 400-1000KHz, and frequency is corresponding with umber of pulse, frequency and umber of pulse product Less than 2000.

4. according to the laser pulse method of the back of the body passivation solaode described in claim 1, it is characterised in that: described passivating film For aluminium oxide, silicon nitride or silicon oxide film or the stack membrane of at least a part of which bi-material, thicknesses of layers is 50-300 nm.

5. according to the laser pulse method of the back of the body passivation solaode described in claim 1, it is characterised in that: described source, laser apparatus Standby for psec, submicrosecond or nanosecond laser.