Silicon atoms have four outer electrons. If atoms with five outer electrons, such as phosphorus atoms, are added to pure silicon, it becomes an N-type semiconductor; if atoms with three outer electrons, such as boron atoms, are added, it forms a P-type semiconductor. When P-type and N-type atoms are combined, a potential difference is created at the interface, forming a solar cell. When sunlight shines on the PN junction, holes move from the P-region to the N-region, and electrons move from the N-region to the P-region, forming an electric current.
The photoelectric effect is the phenomenon that light causes a potential difference between different parts of a non-uniform semiconductor or a semiconductor-metal bond. It involves two main processes: first, the conversion of photons (light waves) into electrons, and light energy into electrical energy; second, the formation of a voltage.
Individual solar cells cannot be used directly as power sources. To function as power sources, several individual cells must be connected in series and parallel and tightly packaged into a module. Solar cell modules (also called solar panels) are the core and most important component of a solar power generation system. Their function is to convert solar energy into electrical energy, which can then be either stored in batteries or used to power loads.
For positive and negative charges, since the positive and negative charges are separated in the PN junction region, an external current field can be generated. Current flows from the bottom of the crystalline silicon solar cell through the load to the top of the cell. This is the "photovoltaic effect." When a load is connected between the top and bottom surfaces of the solar cell, current flows through the load, thus generating current in the solar cell. The more photons the solar cell absorbs, the greater the current generated. The energy of a photon is determined by its wavelength. Photons with energy below the base energy cannot produce free electrons, while photons with energy above the base energy will only produce one free electron. The excess energy will cause the cell to heat up, and the resulting energy loss will reduce the efficiency of the solar cell.
December 3 (Cailian Press) – JinkoSolar has announced that the first batch of photovoltaic modules temporarily detained by the company have been released by U.S. Customs. The exact quantity released and whether there have been any changes to the relevant inspection procedures are still being verified. Previously, industry information indicated that a large number of JinkoSolar modules manufactured using Wacker polysilicon had already appeared on the U.S. market and were already being installed.
The article explained the working principle of the photonics board, and I think it was quite helpful. I hope it can be of assistance.
In 1954, the first single-crystal photonics plate was invented, and in 1958, the first polycrystalline photonics plate began to appear, a difference of four years. As for the differences between them, there should be an introduction on Baidu, so I will not go into details here. As for how to distinguish them, I have also posted photos in the previous article. For the sake of easy observation and identification, I will post them again today.
This article focuses on the specific composition and electrical parameters of the photonic board.
The photonics board mainly consists of the following 8 parts:
1. Backsheet: A composite film made of multiple layers of polymer films bonded together by rolling, which protects and supports the battery cells and has reliable insulation, water resistance and aging resistance.
2. EVA: EVA film is used for encapsulating battery components.
3. Solder strip: Used for electrical connection of cells within the battery assembly.
4. Solar Cells. The core component of a solar cell module, consisting of semiconductor solar cells that have undergone doping, diffusion, and sintering.
5. Glass: It provides support and sufficient mechanical strength for the battery assembly.
6. Silicone: for sealing.
7. Aluminum profile: frame.
8. Junction box: generates electrical energy and outputs it to electrical appliances or other equipment.
The power generation efficiency of a single solar cell is relatively low. For example, a 156*156 solar cell only has a power of a little over 3W, which is far from meeting the needs. Therefore, multiple solar cells need to be connected in series. The solar cells connected in series are called a solar cell string.
In the diagram above, the diode acts as a bypass to prevent hot spot effects, ensuring that the entire module does not fail to generate electricity if one of the cells malfunctions.
The main parameters used to measure the performance of a photonics board are as follows:
1. Maximum power Pmax: The maximum power that the power supply can reach in a short period of time.
2. Optimal operating point current Imp: The current corresponding to the maximum output power Pmax.
3. Optimal operating point voltage Vmp: The voltage corresponding to the maximum output power.
4. Open-circuit voltage Voc: The voltage value corresponding to when the two ends are open.
5. Short-circuit current Isc: The current passing through both ends of the photonic board when the output is short-circuited.
6. Conversion efficiency η: Photoelectric conversion efficiency, which is the ratio of maximum power Pmax to incident power.
7. Fill factor FF: The ratio of maximum power Pmax to the power generated by the ideal battery, between 0.5 and 0.8.
If light shines on a solar cell and is absorbed at the interface layer, photons with sufficient energy can excite electrons from covalent bonds in both P-type and N-type silicon, creating electron-hole pairs. Before recombination, the electrons and holes near the interface layer are separated by the electric field of the space charge. Electrons move towards the positively charged N-region, and holes move towards the negatively charged P-region.
Through charge separation at the interface layer, an outward measurable voltage will be generated between the P-region and the N-region. Electrodes can then be added to both sides of the silicon wafer and connected to a voltmeter. For crystalline silicon solar cells, the typical value of the open-circuit voltage is 0.5 to 0.6 V. The more electron-hole pairs generated at the interface layer by light, the greater the current. The more light energy absorbed by the interface layer, the larger the area of the interface layer, i.e. the cell, the greater the current formed in the solar cell [2].
When sunlight shines on a semiconductor pn junction, new electron-hole pairs are formed. Under the influence of the built-in electric field of the pn junction, holes flow from the n-region to the p-region, and electrons flow from the p-region to the n-region. When the circuit is connected, an electric current is formed. This is the working principle of a solar cell based on the photoelectric effect.
The direct photovoltaic (PV) conversion method utilizes the photovoltaic effect to directly convert solar radiation energy into electrical energy. The basic device for this conversion is the solar cell. A solar cell is a device that directly converts solar energy into electrical energy due to the photovoltaic effect. It is a semiconductor photodiode. When sunlight shines on the photodiode, it converts the sunlight into electrical energy, generating a current. Many cells connected in series or parallel can form a solar cell array with a relatively large output power. Solar cells are a promising new type of power source, possessing three major advantages: permanence, cleanliness, and flexibility. Solar cells have a long lifespan; as long as the sun exists, solar cells can be used for a long time with a one-time investment. Compared to thermal power generation and nuclear power generation, solar cells do not cause environmental pollution.
The main principle of photovoltaic power generation is the photoelectric effect of semiconductors. When a photon shines on a metal, its energy can be completely absorbed by an electron in the metal. If the absorbed energy is large enough, the electron can overcome the internal attraction of the metal and escape from the metal surface, becoming a photoelectron. Silicon atoms have four outer electrons. If atoms with five outer electrons, such as phosphorus atoms, are added to pure silicon, it becomes an N-type semiconductor; if atoms with three outer electrons, such as boron atoms, are added, it forms a P-type semiconductor. When P-type and N-type semiconductors are combined, a potential difference is formed at the interface, forming a solar cell. When sunlight shines on the PN junction, holes move from the P-region to the N-region, and electrons move from the N-region to the P-region, forming an electric current.
