Preparation of silicon materials by physical method and Siemens method
1. Physical methods to produce solar-grade (SOG) silicon In the manufacturing cost of crystalline silicon solar cells, polysilicon raw materials account for a large proportion. In order to reduce the manufacturing cost of polysilicon materials, the polysilicon materials can be purified by physical methods (sometimes called metallurgical methods) or a combination of physical methods and chemical…
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Efficiency and characteristics of solar cells
1. Efficiency of solar cells The photoelectric conversion efficiency n of a solar cell is the ratio of the output electrical power to the incident light power when the solar cell is illuminated by light, referred to as cell efficiency, which can be expressed as where Ai is the area of the solar cell; Pin is the…
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Equivalent circuit, output power and fill factor
1) Equivalent circuit Figure 1 shows the equivalent circuit of a solar cell under stable illumination. It consists of the following circuit elements: a current source capable of generating a photocurrent IL, a diode VD under forward bias, a resistor Rsh in parallel with the diode, a capacitor Cf, and a resistor Rs in series with the…
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Photocurrent and photovoltage
The illumination characteristics of silicon solar cells are shown in Figure 1. It can be seen from the figure that the short-circuit current increases linearly with the increase of light intensity, the open-circuit voltage increases exponentially with the increase of light intensity, and tends to be saturated under strong light. The I-U characteristic curves of…
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Construction and working principle of silicon solar cells
Concentration knot浓度结 When two crystalline silicons with the same conductivity type and different doping concentrations are in contact, a concentration junction (also called a gradient junction) with a galvanic double layer and a self-built electric field can also be formed, as shown in Figure 1. For P-type silicon, the contact barrier height eUg at the junction…
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Semiconductor PN junction
Two pieces of uniformly doped P-type silicon and N-type silicon with doping concentrations of NA and ND, respectively. At room temperature, the impurity atoms are all ionized, and holes with a concentration of pp and electrons (minority carriers) with a concentration of np are distributed in P-type silicon; electrons with a concentration of nn and holes (minority carriers) with a…
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Carrier transport properties and non-equilibrium carriers
Carrier transport properties Under the action of an external electric field and a magnetic field, the movement of electrons and holes in crystalline silicon leads to the transport of electric charges and generates electric current. At 300K, the resistivity of uncompensated or lightly compensated silicon material versus shallow impurity concentration is shown in Figure 1.…
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Carrier concentration of doped semiconductors
The carrier concentration in doped semiconductors changes with temperature, and experiences weak ionization region, intermediate ionization region, strong ionization region, transition region and intrinsic excitation region from low temperature to high temperature. The carrier concentration of doped semiconductors can be calculated and analyzed by quantum statistics theory. There are a large number of energy states…
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N-type crystalline silicon and P-type crystalline silicon
(1) N-type crystalline silicon When crystalline silicon is doped with a small amount of impurity group V elements (such as P), its 5 valence electrons form 4 covalent bonds with silicon atoms, and the V group ion nucleus has one more positive charge, forming a positive center, and one more valence electron. This electron is bound…
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Energy bands and intrinsic semiconductor silicon vs. extrinsic semiconductor silicon
1. Band structure of crystalline silicon The energy bands of a crystal reflect the interactions between the various atoms in the crystal, especially the outer electrons. One energy level of n isolated atoms is split into n closely spaced near-continuous energy levels, forming an energy band, as shown in Figure 1. 2. Energy Band Model…
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