Knowledge introduction of solar cells and their components

Knowledge introduction of solar cells and their components

  1. The history of solar cells
    In 1839, Alexandre-Edmond Becquerel, a French physicist at the time, observed that shining light into a conductive solution would produce electric current and a photovoltaic effect (Photovoltaic Effect). But it was not until 1883 that the first solar cell was manufactured by American scientist Charles Frits, who coated a thin layer of gold on the semiconductor material selenium to form a simple battery. This solar cell has only 1% energy conversion efficiency. In 1927, scientists used metallic copper and semiconductor copper oxide to make solar cells. By 1930, selenium batteries and copper oxide batteries had been applied to some light-sensitive instruments, such as photometers.

The first silicon solar cell was developed by Russell Ohl in the United States in 1946. In 1954, Bell Labs developed a silicon solar cell with a conversion efficiency of 6% and applied it to the first artificial satellite.

  1. Solar cell
    Solar cells are essentially “diodes” under sunlight, and the basis of their energy conversion is the photovoltaic effect of semiconductor PN junctions. When sunlight hits the “diode” PN junction, photo-generated electron-hole pairs are generated in the semiconductor. These photogenerated electrons and holes migrate to the two ends of the PN junction and accumulate on the boundary, thereby forming a photogenerated electric field and electromotive force (photovoltaic effect), which is the principle of solar cells.
  2. Classification of solar cells
    There are many types of solar cells, which can be roughly divided into single crystal, polycrystalline, amorphous and other types. Generally, academically, solar cells are classified according to the materials used to manufacture the cells. The solar modules discussed in this article are all crystalline silicon solar cells.
  3. Solar cell components
    Solar cells made of monolithic monocrystalline silicon or polycrystalline silicon are called monomers. If a large battery is composed of multiple cells connected in series and in parallel, and fixed with an aluminum alloy frame, the surface is covered with high-strength, high-transmittance glass to form a solar cell module, also called a solar cell module. A square array composed of several components (modules) is called a solar cell array.

Usually the power of each module ranges from a few watts to hundreds of watts. These modules can be produced according to the same standard, which is beneficial for large-scale mass production and installation.

  1. Common specifications of solar cells
    The specifications of monocrystalline silicon and polycrystalline silicon solar cells produced in large quantities in the industry are basically 5in and 6in (1in≈2.54㎝), only the diagonal will be different.

In the initial stage of the solar cell industry, the raw material silicon wafers for the production of solar cells are expensive. Therefore, the early solar cells are all round, and saving raw materials as much as possible is the basis for cost-saving in the early production of cells. In the past 20 years, due to the continuous reduction of technology and costs, the price of raw materials has fallen, but the price of silicon wafers no longer plays a decisive role, and the prices of other auxiliary materials have continued to rise, and some have approached 1/5 of the price of silicon wafers. Since then, quasi-square cells have appeared for the purpose of saving auxiliary materials.

In recent years, the efficiency of solar cells produced by conventional processes has risen to close to the theoretical limit, and cost reduction can only move in the direction of overall cost reduction, and square monocrystalline silicon cells have begun to appear. At the same time, because of the characteristics of the production process of polycrystalline silicon, polycrystalline silicon cells have been used in the market in a square shape. In addition, because of the continuous improvement of the production process of polycrystalline silicon cells, the performance indicators of silicon wafers produced from polycrystalline silicon are close to those produced by monocrystalline silicon and are widely used. In the future, more square cells will be seen.

  1. Common specifications of solar cell modules
    The specifications of the components are mainly constrained by two aspects, namely power and voltage. There are many changes in daily application specifications, but for large-scale power stations and rooftop solar power generation systems, the size changes are relatively simple.

The main open-circuit voltage is required to be controlled above 45V. Commonly used are 5in monocrystalline silicon 72 pieces connected in series, the size is 1580mm×808mm, the thickness is 35mm, 42mm, 50mm, and the power range is 175~215W; 6in monocrystalline silicon 72 pieces connected in series Method, size is 1956mm×92mm, thickness is 42mm, 50mm, power range is 265~320w; 72 pieces of 6in polysilicon are connected in series, size is 1956mm×92mm, thickness is 42mm, 50mm, power range is 250~300w, main open circuit is required For voltage control above 36V, there are common 6in monocrystalline silicon 60 pieces in series, the size is 1652mm×92mm, the thickness is 42mm, 50mm, and the maximum power is above 250W; 6in polysilicon 60 pieces in series, the size is 1652mm×92mm, The thickness is 42mm, 50mm, and the maximum power is above 230W.

The main open circuit voltage is required to be controlled above 33V. Commonly used are 54 pieces of 6in polysilicon in series, the size is 1494mm×92mm, the thickness is 42mm, 50mm, and the maximum power is more than 210W.

In recent years, large-scale Building Integrated Photo Voltaics (BIPV) modules have been widely used. The corresponding specifications and dimensions vary according to the structure, and are often designed according to the shape of the building. This section will not be detailed. Narrated.