1. Polarity of solar cell modules
The silicon solar cell module is generally made into a P+/N type structure or an N+/P type structure. The first symbol P+ in front of the P+/N type structure indicates that the conductivity type of the semiconductor material on the front side of the solar cell is P-type; the second symbol N indicates that the conductivity type of the semiconductor material on the backside of the solar cell is N-type. When sunlight is irradiated, the polarity of the output voltage of the solar cell is positive on the P-type side electrode, and negative on the N-type side electrode. The first symbol N+ in front of the N+/P type structure indicates that the conductivity type of the semiconductor material on the front side of the solar cell is N-type; the second symbol P indicates that the conductivity type of the semiconductor material on the backside of the solar cell is P-type.
When the solar cell is connected to an external circuit as a power source, the solar cell works in a forward state. When the solar cell is used in combination with other power sources, if the positive electrode of the external circuit is connected to the P electrode of the battery and the negative electrode is connected to the N electrode of the battery, the external power source provides forward bias to the solar cell; if the positive electrode of the external power source is connected to the battery’s N electrode The N electrode is connected, and the negative electrode is connected to the P electrode, and the external power supply provides reverse bias voltage to the solar cell.
2. Basic requirements for solar cell modules
A solar cell module with good performance should meet the following requirements:
① long working life (should be more than 20 years), low packaging cost;
②Good sealing performance, windproof, waterproof and anti-corrosion;
③High mechanical strength, impact resistance and vibration resistance;
④Good electrical insulation performance and anti-ultraviolet radiation ability;
⑤ There are a variety of wiring methods that can meet different voltage, current and power output requirements;
⑥ The welding between solar cells is required to be straight and firm, and when the solar cells are combined in series and parallel, the loss of photoelectric conversion efficiency is not large.
Regardless of the power of the battery module, the number and arrangement of the internal cells are generally composed of 36 cells, 72 cells, 54 cells and 60 cells in series. Common arrangement methods are 4 pieces × 9 pieces, 6 pieces × 6 pieces, 6 pieces × 12 pieces, 6 pieces × 9 pieces and 6 pieces × 10 pieces.
