Solar cell - an electronic device which converts the photon energy into electrical energy. The first solar cell based on the external photoelectric effect, created the Alexander Stoletov in the late XIX century.
The most effective, in terms of energy, devices for converting solar energy into electricity are solid-state photovoltaic cells (solar cells), because it is a direct, one-step transition of power. CAP produced on an industrial scale cells on average 16%, the best samples of up to 25%. Under laboratory conditions has been achieved 43.5% efficiency.
The physical principle of operation of the photocell
Energy conversion in solar cells based on the photoelectric effect, which occurs in inhomogeneous semiconductor structures when exposed to solar radiation.
The heterogeneity of the structure of solar cells can be obtained by doping the same semiconductor with different impurities (the creation of pn junctions) or by combining different semiconductors with varying band gaps - energies of electron detachment from the atom (the creation of heterojunctions), or by changing the chemical composition of the semiconductor, resulting in the appearance of the gradient of the band gap (the creation of graded-gap structures). There are also various combinations of the following methods.
The conversion efficiency depends on the electrophysical characteristics of inhomogeneous semiconductor structure and optical properties of solar cells, among which the most important role is played by photoconductivity. It is due to the internal phenomena in semiconductors irradiated by sunlight.
Major irreversible losses of energy in solar cells are associated with:
-reflection of sunlight from the surface of the transducer,
-the passage of radiation through the absorption of solar cells, without it,
-scattering by thermal vibrations of the excess energy of photons
-recombination of photo-pairs formed on surfaces and in the amount of solar cells,
-internal resistance of the transducer,and some other physical processes.
To reduce all forms of energy loss in solar cells are developed and successfully used a variety of activities. Among them are:
-use of semiconductors with the optimum for solar energy gap;
-addressed to improve the properties of the semiconductor structure by its optimal doping, and a built-in electric fields;
-transition from homogeneous to heterogeneous and graded gap semiconductor structures;
-optimization of design parameters of solar cells (the depth of the pn junction, the thickness of the base layer, the frequency of the contact grid, etc.);
-the use of multifunctional optical coatings that provide illumination, temperature control and protection from cosmic radiation, solar cells;
Development of solar cells, transparent in the wavelength region of the solar spectrum at the fundamental absorption edge;
the creation of cascade solar cells of specially selected by the band gap semiconductors, allowing to convert in each stage of radiation passing through the previous stage, and so on;
Also, a significant increase in efficiency of solar cells has been achieved through the creation of probes with two-way sensitivity (up to 80% efficiency to an existing one hand), the use of luminescent reradiating structures, pre-expansion of the solar spectrum into two or more spectral regions with multilayer thin-film beamsplitters (dichroic mirrors ), followed by conversion of each plot range of individual solar cells, etc.
Materials:
Solar cells made from different semiconductor materials. The manufacture of photocell close to the manufacturing processes of other semiconductor devices such as chips.
Monocrystalline solar cells most difficult and expensive because their manufacture requires crystalline silicon, but with the greatest efficiency (14% -20% conversion of light into electricity).
Polycrystalline, or multykrystalichni solar cells cheaper than single crystal, but are less effective.
Thin film solar cells using thin films made of fused silica. Such solar cells less effective.
In the space vehicles used as solar cells or bahatoperehidni heterophotocells. This element consists of several pn junctions (AlGaAs-GaAs), each of which captures a light spectrum. Such solar cells achieve peak performance - 35%. The complexity of making such devices makes them rare.
To improve the efficiency of conversion of light is also used kontsentruvalnu optics.
In our research is underway to create a flexible thin film solar cells and semiconductor inks, use of organic semiconductors.
temperature
An important aspect of solar cells is their temperature. Upon heating element one degree over 25 ° C it loses voltage 0.002 V, ie 0.4% / degree. This is a problem for solar cells with kontsentruvalnoyu optics. Therefore, they require additional cooling.
The most effective, in terms of energy, devices for converting solar energy into electricity are solid-state photovoltaic cells (solar cells), because it is a direct, one-step transition of power. CAP produced on an industrial scale cells on average 16%, the best samples of up to 25%. Under laboratory conditions has been achieved 43.5% efficiency.
 |
| Solar cell based on polycrystalline silicon |
The physical principle of operation of the photocell
Energy conversion in solar cells based on the photoelectric effect, which occurs in inhomogeneous semiconductor structures when exposed to solar radiation.
The heterogeneity of the structure of solar cells can be obtained by doping the same semiconductor with different impurities (the creation of pn junctions) or by combining different semiconductors with varying band gaps - energies of electron detachment from the atom (the creation of heterojunctions), or by changing the chemical composition of the semiconductor, resulting in the appearance of the gradient of the band gap (the creation of graded-gap structures). There are also various combinations of the following methods.
The conversion efficiency depends on the electrophysical characteristics of inhomogeneous semiconductor structure and optical properties of solar cells, among which the most important role is played by photoconductivity. It is due to the internal phenomena in semiconductors irradiated by sunlight.
Major irreversible losses of energy in solar cells are associated with:
-reflection of sunlight from the surface of the transducer,
-the passage of radiation through the absorption of solar cells, without it,
-scattering by thermal vibrations of the excess energy of photons
-recombination of photo-pairs formed on surfaces and in the amount of solar cells,
-internal resistance of the transducer,and some other physical processes.
To reduce all forms of energy loss in solar cells are developed and successfully used a variety of activities. Among them are:
-use of semiconductors with the optimum for solar energy gap;
-addressed to improve the properties of the semiconductor structure by its optimal doping, and a built-in electric fields;
-transition from homogeneous to heterogeneous and graded gap semiconductor structures;
-optimization of design parameters of solar cells (the depth of the pn junction, the thickness of the base layer, the frequency of the contact grid, etc.);
-the use of multifunctional optical coatings that provide illumination, temperature control and protection from cosmic radiation, solar cells;
Development of solar cells, transparent in the wavelength region of the solar spectrum at the fundamental absorption edge;
the creation of cascade solar cells of specially selected by the band gap semiconductors, allowing to convert in each stage of radiation passing through the previous stage, and so on;
Also, a significant increase in efficiency of solar cells has been achieved through the creation of probes with two-way sensitivity (up to 80% efficiency to an existing one hand), the use of luminescent reradiating structures, pre-expansion of the solar spectrum into two or more spectral regions with multilayer thin-film beamsplitters (dichroic mirrors ), followed by conversion of each plot range of individual solar cells, etc.
Materials:
Solar cells made from different semiconductor materials. The manufacture of photocell close to the manufacturing processes of other semiconductor devices such as chips.
Monocrystalline solar cells most difficult and expensive because their manufacture requires crystalline silicon, but with the greatest efficiency (14% -20% conversion of light into electricity).
Polycrystalline, or multykrystalichni solar cells cheaper than single crystal, but are less effective.
Thin film solar cells using thin films made of fused silica. Such solar cells less effective.
In the space vehicles used as solar cells or bahatoperehidni heterophotocells. This element consists of several pn junctions (AlGaAs-GaAs), each of which captures a light spectrum. Such solar cells achieve peak performance - 35%. The complexity of making such devices makes them rare.
To improve the efficiency of conversion of light is also used kontsentruvalnu optics.
In our research is underway to create a flexible thin film solar cells and semiconductor inks, use of organic semiconductors.
temperature
An important aspect of solar cells is their temperature. Upon heating element one degree over 25 ° C it loses voltage 0.002 V, ie 0.4% / degree. This is a problem for solar cells with kontsentruvalnoyu optics. Therefore, they require additional cooling.
Comments (0)
Отправить комментарий