Solar cell is a kind of effect will use photovoltaic solar energy directly into electrical energy devices. The photovoltaic effect in solids, especially in the semiconductor, high energy conversion efficiency, it is also known as solar cells, semiconductor solar cells.
A solar cell works
Solar energy is converted into electrical energy to energy conversion, solar cells based on the working principle of semiconductor PN junction photovoltaic effect.
In the pure silicon crystal, the number of free electrons and holes are equal. If the incorporation of silicon to capture electrons boron, aluminum, gallium or indium and other impurities to form P-type semiconductor, if the incorporation of silicon to release electrons of phosphorus, arsenic or antimony and other impurities to constitute the N-type semiconductor. If you combine these two semiconductors, the interface will form at the PN junction, and junction formation on both sides of the barrier electric field. When the sunlight when the PN junction in the semiconductor light atoms obtained the release of the e-produce electron – hole pairs in the barrier effect of the electric field, electrons are driven to the N-type area, was driving to the hole P-type area, which formed near the PN junction with the barrier photo electric field in the opposite direction (Figure 1). Part of photo-electric barrier field off, the rest makes the N-type region and a thin layer of P-type area created between the electromotive force, that is, photovoltaic force, when connected to external circuit will have electrical power. This is the type of silicon PN junction contact with the basic principles of solar power generation. If the dozens, hundreds of single solar cells in series, parallel together to form solar modules, in the sunlight irradiation, the output power can be obtained considerable power.
2, the structure and parameters of solar cells
2.1 The structure of solar cells
The simplest structure of solar cells into by the PN. Shown in Figure 2, the gate line on the surface of the electrode on the shape of the back of the back electrode, the solar cell surface usually coated with a layer of antireflection coating.
2.2 The parameters of solar cells
Open circuit voltage Uoc: solar cells by light in the open state, the light carriers can accumulate at the PN junction photo-electromotive force on both sides of solar cells when measured at both ends of the electrical potential difference.
Short circuit current Isc: short circuit of solar cells measured from outside the maximum current.
Maximum output power Pm: Pm = UmIm, the load resistance to the product of output voltage and current maximum output power.
Fill factor FF: maximum output power and the open circuit voltage and short circuit current ratio of the product.
Conversion efficiency: the best in the external loop connecting the load resistor, the maximum energy conversion efficiency, equal to the output of solar power and energy of the incident to the solar surface ratio.
3 Classification of solar cells
3.1 Structure Classification
Homojunction solar cells: a semiconductor material by the same constitute one or more PN junction solar cells.
For example, silicon solar cells, GaAs solar cells.
Heterojunction solar cells: two different band gap semiconductor material in the phase of the interface to form a PN junction heterojunction solar cells. For example, indium tin oxide / silicon solar cells, cuprous sulfide / cadmium sulfide solar cells. If the crystal structure of two heterogeneous materials similar to better lattice matching at the interface, called the heterogeneity of its surface solar cells. For example, AlGaAs / GaAs heterojunction solar cells surface.
Schottky junction solar cells: The formation of a metal and semiconductor contacts, “Schottky barrier” of solar cells, solar cells, also known as MS. At present, this structure has developed into the battery metal – oxide – semiconductor solar cells (MOS); metal – insulator – semiconductor solar cells (MIS). For example, Pt / Si Schottky junction solar cells, Al / Si Schottky junction solar cells.
3.2 Classification by Material
Silicon solar cells: the silicon substrate material. Such as single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells. CdS solar cells: the CdS single crystal or crystal as the matrix material. For example, cuprous sulfide / cadmium sulfide solar cells, CdTe / CdS solar cells, copper indium selenide / cadmium sulfide solar cells. GaAs solar cells: the GaAs substrate material. For example, gallium arsenide homojunction solar cells, GaAs heterojunction solar cells. Solar cell structure according to the classification of its relatively clear physical meaning, which the country has been adopted as the basis for solar cell naming.
4, the design and selection of solar modules
Solar cells convert light energy into electrical energy is the smallest unit, that a single solar cell. To meet the actual requirements, shall the electrical properties of a number of single cell classification by series and parallel, can be encapsulated to form after independence as a power source using solar modules.
4.1 The technical requirements for solar modules
Terrestrial applications of solar components require good electrical insulation, adequate mechanical strength, lower cost, the combination of efficiency loss due to the small, long life components and materials used, the service life of components and its structure consistent. Currently the most widely used crystalline silicon PV modules are solar modules.
4.2 The connection of solar modules
Production of solar modules, you should choose the same electrical performance parameters of the monomer combination and package of solar cells in order to ensure minimal loss of solar cells combined. According to the nominal operating voltage to determine the number of single solar cells in series, according to the nominal output power to determine the number of solar cells in parallel (Figure 3). To save packaging materials, to make reasonable arrangement of solar cells, so that the total area as small as possible. Common peak power output of solar cell module has 8,10,20,36,40, 50,75,160 W and so on. High-power solar power generation system shall connect multiple components into a matrix, as shown in Figure 4.
4.3 The package of solar modules Solar panel in a single solar cell is connected between the conductive metal welding with a series or in parallel. Crystalline silicon solar cells currently used in the packaging process as follows.
Followed by the steel white glass-EVA (ethylene vinyl acetate copolymer) – solar film – siphon glass-EVA-PVF (polyvinyl fluoride) films stack up, into the packaging machine for packaging laminate.
Crystalline silicon solar cells of all packaging material must have good weather resistance, the request can be used outdoors in the sun more than 20a. Tempered glass is low iron glass, light transmission is generally 90%. EVA film to add a UV crosslinking agents, solar cells laminated package, after about 150 ℃ heat treatment, crosslinking agent crosslinking the EVA film with a certain flexibility in the formation of protective layer. EVA membrane to prevent the bubble, to the heat treatment under vacuum. Solar cells used in the back of PVF composite film, usually white, with good weather resistance. The middle layer of composite membrane with a polyester film, both sides of the PVF membrane structure, thickness of about 1mm. Finally, the edge of encryption components and seals the aluminum frame anodized to form a solar cell module (Figure 5)
As the integration of solar components and building the new package is sealed in the solar cells between two layers of tempered glass to increase the strength and light transmission.
4.4 The selection of solar modules
Use of crystalline silicon solar cell components, to check whether the following deficiencies components: ① cracking, bending, is not structured or damage the outer surface;
② a cracked or broken single cells;
③ faulty interconnect or connector;
④ Battery contact with each other or in contact with the border;
⑤ sealing material failure;
⑥ in the component’s border and the battery form a continuous channel between the bubbles or delamination;
⑦ lead terminal failure, exposed live parts;
⑧ junction box is not securely installed. Qualified manufacturers of solar modules should be given in the back of product performance data and test marks.
Solar Cell design and selection of components
Posted by admin in News
Solar cell is a kind of effect will use photovoltaic solar energy directly into electrical energy devices. The photovoltaic effect in solids, especially in the semiconductor, high energy conversion efficiency, it is also known as solar cells, semiconductor solar cells.
A solar cell works
Solar energy is converted into electrical energy to energy conversion, solar cells based on the working principle of semiconductor PN junction photovoltaic effect.
In the pure silicon crystal, the number of free electrons and holes are equal. If the incorporation of silicon to capture electrons boron, aluminum, gallium or indium and other impurities to form P-type semiconductor, if the incorporation of silicon to release electrons of phosphorus, arsenic or antimony and other impurities to constitute the N-type semiconductor. If you combine these two semiconductors, the interface will form at the PN junction, and junction formation on both sides of the barrier electric field. When the sunlight when the PN junction in the semiconductor light atoms obtained the release of the e-produce electron – hole pairs in the barrier effect of the electric field, electrons are driven to the N-type area, was driving to the hole P-type area, which formed near the PN junction with the barrier photo electric field in the opposite direction (Figure 1). Part of photo-electric barrier field off, the rest makes the N-type region and a thin layer of P-type area created between the electromotive force, that is, photovoltaic force, when connected to external circuit will have electrical power. This is the type of silicon PN junction contact with the basic principles of solar power generation. If the dozens, hundreds of single solar cells in series, parallel together to form solar modules, in the sunlight irradiation, the output power can be obtained considerable power.
2, the structure and parameters of solar cells
2.1 The structure of solar cells
The simplest structure of solar cells into by the PN. Shown in Figure 2, the gate line on the surface of the electrode on the shape of the back of the back electrode, the solar cell surface usually coated with a layer of antireflection coating.
2.2 The parameters of solar cells
Open circuit voltage Uoc: solar cells by light in the open state, the light carriers can accumulate at the PN junction photo-electromotive force on both sides of solar cells when measured at both ends of the electrical potential difference.
Short circuit current Isc: short circuit of solar cells measured from outside the maximum current.
Maximum output power Pm: Pm = UmIm, the load resistance to the product of output voltage and current maximum output power.
Fill factor FF: maximum output power and the open circuit voltage and short circuit current ratio of the product.
Conversion efficiency: the best in the external loop connecting the load resistor, the maximum energy conversion efficiency, equal to the output of solar power and energy of the incident to the solar surface ratio.
3 Classification of solar cells
3.1 Structure Classification
Homojunction solar cells: a semiconductor material by the same constitute one or more PN junction solar cells.
For example, silicon solar cells, GaAs solar cells.
Heterojunction solar cells: two different band gap semiconductor material in the phase of the interface to form a PN junction heterojunction solar cells. For example, indium tin oxide / silicon solar cells, cuprous sulfide / cadmium sulfide solar cells. If the crystal structure of two heterogeneous materials similar to better lattice matching at the interface, called the heterogeneity of its surface solar cells. For example, AlGaAs / GaAs heterojunction solar cells surface.
Schottky junction solar cells: The formation of a metal and semiconductor contacts, “Schottky barrier” of solar cells, solar cells, also known as MS. At present, this structure has developed into the battery metal – oxide – semiconductor solar cells (MOS); metal – insulator – semiconductor solar cells (MIS). For example, Pt / Si Schottky junction solar cells, Al / Si Schottky junction solar cells.
3.2 Classification by Material
Silicon solar cells: the silicon substrate material. Such as single crystal silicon solar cells, polycrystalline silicon solar cells, amorphous silicon solar cells. CdS solar cells: the CdS single crystal or crystal as the matrix material. For example, cuprous sulfide / cadmium sulfide solar cells, CdTe / CdS solar cells, copper indium selenide / cadmium sulfide solar cells. GaAs solar cells: the GaAs substrate material. For example, gallium arsenide homojunction solar cells, GaAs heterojunction solar cells. Solar cell structure according to the classification of its relatively clear physical meaning, which the country has been adopted as the basis for solar cell naming.
4, the design and selection of solar modules
Solar cells convert light energy into electrical energy is the smallest unit, that a single solar cell. To meet the actual requirements, shall the electrical properties of a number of single cell classification by series and parallel, can be encapsulated to form after independence as a power source using solar modules.
4.1 The technical requirements for solar modules
Terrestrial applications of solar components require good electrical insulation, adequate mechanical strength, lower cost, the combination of efficiency loss due to the small, long life components and materials used, the service life of components and its structure consistent. Currently the most widely used crystalline silicon PV modules are solar modules.
4.2 The connection of solar modules
Production of solar modules, you should choose the same electrical performance parameters of the monomer combination and package of solar cells in order to ensure minimal loss of solar cells combined. According to the nominal operating voltage to determine the number of single solar cells in series, according to the nominal output power to determine the number of solar cells in parallel (Figure 3). To save packaging materials, to make reasonable arrangement of solar cells, so that the total area as small as possible. Common peak power output of solar cell module has 8,10,20,36,40, 50,75,160 W and so on. High-power solar power generation system shall connect multiple components into a matrix, as shown in Figure 4.
4.3 The package of solar modules
Solar panel in a single solar cell is connected between the conductive metal welding with a series or in parallel. Crystalline silicon solar cells currently used in the packaging process as follows.
Followed by the steel white glass-EVA (ethylene vinyl acetate copolymer) – solar film – siphon glass-EVA-PVF (polyvinyl fluoride) films stack up, into the packaging machine for packaging laminate.
Crystalline silicon solar cells of all packaging material must have good weather resistance, the request can be used outdoors in the sun more than 20a. Tempered glass is low iron glass, light transmission is generally 90%. EVA film to add a UV crosslinking agents, solar cells laminated package, after about 150 ℃ heat treatment, crosslinking agent crosslinking the EVA film with a certain flexibility in the formation of protective layer. EVA membrane to prevent the bubble, to the heat treatment under vacuum. Solar cells used in the back of PVF composite film, usually white, with good weather resistance. The middle layer of composite membrane with a polyester film, both sides of the PVF membrane structure, thickness of about 1mm. Finally, the edge of encryption components and seals the aluminum frame anodized to form a solar cell module (Figure 5)
As the integration of solar components and building the new package is sealed in the solar cells between two layers of tempered glass to increase the strength and light transmission.
4.4 The selection of solar modules
Use of crystalline silicon solar cell components, to check whether the following deficiencies components: ① cracking, bending, is not structured or damage the outer surface;
② a cracked or broken single cells;
③ faulty interconnect or connector;
④ Battery contact with each other or in contact with the border;
⑤ sealing material failure;
⑥ in the component’s border and the battery form a continuous channel between the bubbles or delamination;
⑦ lead terminal failure, exposed live parts;
⑧ junction box is not securely installed. Qualified manufacturers of solar modules should be given in the back of product performance data and test marks.