Light and heat absorption: the basic principle of photovoltaic power generation

The photovoltaic effect (that is, the photovoltaic effect) refers to an effect of electromotive force and current generated when the object is exposed to light, due to the absorption of light energy, the transition of electrons, and the change in the charge distribution state within the object.

According to the characteristics of the semiconductor, the semiconductor has two kinds of current carriers of electrons and holes (refers to the matter particles with charges that can move freely, referred to as “carriers”), in which electrons are negatively charged and holes are positively charged, and a certain carrier in the semiconductor material accounts for the majority, then it is called many, and a small part is the minority. Silicon is the most basic material is “silicon”, pure silicon does not conduct electricity, but can be doped in silicon to change the characteristics: in the silicon crystal with boron element, you can make P-type silicon; By adding phosphorus, N-type silicon wafers can be made. Due to the different price characteristics of boron and phosphorus, the holes in P-type silicon wafers are mainly involved in conducting electricity as many carriers, and the electrons are a few carriers (few carriers). The electrons in the N-type silicon chip are mainly involved in conducting electricity as many moles, and the holes are few moles. The above P (Positive, positive charge) and N (Negative, negative charge) are named according to the positive and negative charge of the silicon chip.

PNjunction (junction refers to cross, translated from English “PNjunction”) is the basic structural unit of a photovoltaic cell, which is usually formed at the junction of the P-type region and the N-type region in the same silicon wafer, and can be obtained by diffusing phosphorus to the surface of the P-type silicon wafer or boron to the surface of the N-type silicon wafer.

Photovoltaic cell power generation is to use the potential difference of free electrons generated by the PN junction position to generate current. When the sun shines on the surface of the battery, the electrons absorb energy into moving free electrons, and at the same time form holes in the original position. The free electrons will move to the N region under the action of the internal electric field, and the corresponding holes will move to the P region. When the positive and negative electrodes of the battery are connected to form a closed circuit, the free electrons are moved from the N region through the wire to the P region by the force of the internal electric field, and the current is generated in the outer circuit.