Photovoltaic power generation is a technology that directly converts light energy into electrical energy by using the photovoltaic volts effect of the semiconductor interface. The key component of this technology is the solar cell. After the solar cell is encapsulated and protected in series, a large area of solar cell modules can be formed, and then combined with components such as power controllers, a photovoltaic power generation device is formed.
Principle of solar cell power generation
1. N-type semiconductors and P-type semiconductors
Intrinsic semiconductors, is a pure semiconductors with crystal structures form covalent bonds between atoms. The two electrons in the covalent bond are called valence electrons.
Valence electrons can break free from the shackles of the nucleus and become free electrons (negatively charged) after gaining a certain amount of energy (temperature increase or illumination), while leaving a vacancy in the covalent bond,which is called a hole(positively charged). Both free electrons and holes are called carriers, and the number of carriers in intrinsic semiconductors is exceedingly small, the electrical conductivity is very poor.
The incorporation of trace amounts of impurities (some elements) into the intrinsic semiconductor forms an impurity semiconductor, which can enhance its conductivity.
The addition of pentavalent phosphorus replaces the silicon atom, and four of the five outer electrons of the outer layer of the phosphorus atom form a covalent bond with the surrounding semiconductor atoms, and the extra electron is almost unbound and easier to become a free electron. Therefore, the number of free electrons increases after doping, and free electron conduction becomes the main conductive mode of this semiconductor, called N-type semiconductor.
When trivalent boron is incorporated to replace the silicon atom, a "hole" is created when the three outer electrons of the outer layer of the boron atom form a covalent bond with the surrounding semiconductor atoms. Therefore, the number of holes after doping increases significantly, and hole conduction becomes the main conductive method of this semiconductor, called P-type semiconductor.
Both N-type and P-type semiconductors are neutral and do not show electrical properties to the outside.
The electrons of N-type semiconductors are majority carrier, and the holes are minority carrier.
The holes of P-type semiconductors are majority carrier, and the electrons are minority carrier.
2. “PN junction” and “photovoltaic volts effect”
The PN junction is composed of an N-doped region and a P-type doping region in close contact. On a complete piece of silicon wafer, different doping processes are used to form N-type semiconductors on one side and P-type semiconductors on the other side. The region near the interface of the two kinds of semiconductors is the PN junction. The basic structure of a solar cell is a large area planar PN junction.
When sunlight hits the PN junction, the PN junction absorbs light energy to excite electrons and holes, generating voltage in the PN junction, called the "photovoltaic volts effect" or simply the "photovoltaic effect.”
