Sintering is the last key process of Polycrystalline Solar Cells, which determines the efficiency and qualified rate of solar polycrystalline cell, and sintering furnace directly affects the success or failure of sintering process. In this paper, the phenomenon of sintered EL caused by sintering furnace is studied emphatically.
1 screen printing sintering process
Sintering is the printing of the slurry of the wafer through the drying process after the coke, so that most of the organic solvent in the slurry volatile, and then sintered into a battery at high temperatures, and ultimately the electrode and the wafer itself to form an ohmic contact, thus Improve the open circuit voltage and filling factor of the battery chip, the two key factor parameters, so that the contact with the electrode resistance characteristics, to achieve the purpose of producing high conversion efficiency of the battery. Sintering process is conducive to PECVD process introduced by the proliferation of-H to the body, can play a good body passivation. Sintering is a process of diffusion, flow and physical chemistry. In the printing conditions under the premise of stability, temperature zone temperature, gas flow, belt speed is the sintering of the three key parameters.
Analysis of Sintering Abnormality of Solar Polycrystalline Cell
Screen printing section due to sintering furnace peripheral maintenance is not in place, intermittent string resistance caused by high, low efficiency. In the low efficiency of the battery chip EL test found that the EL image part of the region showed a black mist,Polycrystalline Solar Cells such phenomena are mainly due to sintering abnormalities caused.
3 analysis method
Screen printing sintering anomalies mainly from the equipment and process two aspects of experimental analysis and verification.
3.1 Equipment aspects
Equipment mainly from the sintering furnace exhaust and lamp 2 to consider.
3.1.1 Sintering furnace exhaust problem
Compared with the sintering furnace of the polycrystalline workshop and the single crystal workshop, it is found that the sintering furnace of the polycrystalline production line is low, only about 300m3 / h, and the sintering exhaust wind is suspected to be low, which leads to the volatilization of organic matter in the sintering furnace , In the sintering furnace inside the accumulation,Polycrystalline Solar Cells so that organic matter and silicon contact with the pollution of the battery, resulting in sintering abnormalities, low efficiency. Strengthen the sintering furnace organic solvent extraction capacity mainly through the following
1) power plant to improve the frequency of organic exhaust fan;
2) Clean the HTO condenser filter, clean the FF Venturi system, check the internal cavity of the furnace.
3) FF sintering area of process gas compensation and cooling zone fan speed to adjust to ensure that the furnace cavity negative pressure state.
4) 5 lines and 6 lines of organic exhaust pipe to transform the 5-line and 6-wire organic exhaust pipe connected to the screen ordinary exhaust pipe, 7 lines, 8 lines and 9 lines unchanged.
After the treatment of the sintering furnace, the B102 of the sintering furnace increased from 300m3 / h to 500m3 / h, and the pressure difference B112 and B113 increased from about 10Pa to about 20Pa, which greatly enhanced the organic drainage of the sintering furnace ability.
3.1.2 sintering furnace lamp aging problem
The low efficiency of the battery chip EL detection and found that the positive EL image surface black, suspected lamp aging, less than the sintering temperature requirements.
The sintering area of the 5-wire,Polycrystalline Solar Cells 6-wire and 8-wire sintering furnaces was replaced and the power of the upper and lower lamps was adjusted to reduce the trimtop / bottom of the sintered area from 100% to 70% , Efficiency increased by about 0.03%.
3.2 Process aspects
3.2.1 Battery surface contamination
The EL of the low efficiency of the battery EL detection and found that the edge or the whole side of the phenomenon of black, suspected slurry pollution or battery front in the production process with the track contact with the local pollution or sintering furnace pollution point with the front of the battery ,Polycrystalline Solar Cells Polluted the battery. In view of this problem, on the one hand, cleaning the drying furnace track and the machine conveyor belt, on the other hand, open the sintering furnace drying area and cooling zone furnace cavity, clean up the dust and debris, to ensure the cleanliness of the sintering furnace.
3.2.2 sintering internal airflow problem
Polycrystalline battery production line is a two-track production line, found in the production of a normal efficiency of the track, the other track the phenomenon of abnormal efficiency, or monorail production of normal, dual-track abnormal phenomenon. It is suspected that the internal combustion of the sintering furnace in the double-track production is unstable and the sintering temperature is unstable,Polycrystalline Solar Cells resulting in abnormal sintering and low efficiency.
In view of the internal airflow problem in the sintering furnace, the air flow in the sintering furnace sintering area and the fresh air volume in the drying zone are adjusted.