Principles of solar cell power generation
First, N-type semiconductor and P-type semiconductor
Completely pure, crystalline structure of the semiconductor, known as the intrinsic semiconductor, atoms formed between the covalent bond, the structure shown in Figure 1-3. The two electrons in the covalent bond are called valence electrons.
Valence electrons in a certain amount of energy (temperature rise or by light), you can get rid of the nucleus of the bondage, as free electrons (with negative), while the covalent bond left a vacancy, known as the hole (with positive) , Free electrons and holes are called carriers, intrinsic semiconductors in the number of carriers is very small, its poor electrical conductivity.
In the intrinsic semiconductors mixed with trace impurities (some elements), the formation of impurity semiconductors, can greatly enhance the conductivity.
The incorporation of pentavalent phosphorus to replace the silicon atom, the outer layer of phosphorus atoms in the outer layer of five of which formed a covalent bond with the surrounding semiconductor atoms, the extra electron is almost unrestrained, more easily become free electrons The Therefore, the number of free electrons after doping increases, free electron conduction becomes the main conductive mode of this kind of semiconductor, called N-type semiconductor.
Doped with trivalent boron to replace the silicon atoms, boron atoms outer layer of three outer electrons and the surrounding semiconductor atoms to form a covalent bond, it will produce a "hole." Therefore, the number of holes after doping increases, hole conduction becomes the main conductive mode of this kind of semiconductor, called P-type semiconductor.
Whether N-type or P-type semiconductors are neutral, external is not significant.
N-type semiconductor electrons are multi-child, holes are minority;
P-type semiconductor hole is a multi-child, electron is a minority.
Second, "PN junction" and "photovoltaic effect"
The PN junction is made up of an N-type doped region and a P-type doped region. On a complete wafer, the N-type semiconductor is formed on the other side by a different doping process, and the P-type semiconductor is formed on the other side. The area near the interface of the two semiconductors is a PN junction. The basic structure of solar cells is a large area plane PN junction.
When the sunlight is irradiated onto the PN junction, the PN junction absorbs light to excite electrons and holes, producing a voltage in the PN junction, called "photovoltaic effect" or "photovoltaic effect".