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The solar cells are based on the principle of photovoltaic effect.
The solar cells are sandwiched between N-type silicon that contains free electrons and P-type silicon that contains free holes. When N-type and P-type silicon comes into contact, an electric field forms within the cell. Thus, when P and N layers are connected to external circuit, electrons flow from N-layer to P-layer. Hence, current is generated.
The electrons leave the solar cell as current give up their energy to whatever is connected to the solar cell and then re-enter the solar cell.
This is how the process begins again.
Depending upon the efficiency and material of the solar panel, they are categorised into various generations.
These are made of monocrystalline silicon or polysilicon. They served the most commonly its use in conventional surroundings.
These cells includes different types of thin-film solar cells.
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They are mainly useful for photovoltaic power stations, integrated in buildings or smaller solar power systems.
This generation of solar panels include a variety of thin films technologies.
Some of them generate electricity by using organic materials and also inorganic substances like CdTe.
The most commonly used semiconductor material in the production of solar cells is silicon. Polycrystalline thin films like copper indium diselenide, cadmium telluride, and gallium arsenide are also used.
The molecular structure of single-crystal silicon is uniform. This crystal exhibits the ideal transfer of electrons and hence the doping of silicon with other element results in effective photovoltaic cells.
Multi-crystalline silicon posses less efficieny than single-crystal silicon and cheap to produce. Casting process is used for the production.
Amorphous silicon can absorb 40 times more solar radiation than single-crystal silicon i.e. amorphous silicon can reduce the cost of photovoltaics.
Polycrystalline Thin Films - Reducing Material Required in Solar Cells
Large number of thin-film technologies are currently being developed to decrease the amount of light absorbing material required to produce solar cells so that there will be reduction in processing cost. And this will ultimately lead to a reduction in energy conversion efficiency.
Copper indium diselenide has an extremely high absorptivity
It also has a very high absorptivity and can be produced using low-cost techniques. The properties of CdTe can be altered by the addition of mercury and zinc (alloying elements).
Gallium arsenide also has a very high absorptivity. These cells are unaffected by heat and are highly resistant to damage from radiation.
They are generally hybrid organic-inorganic lead or tin-halide materials, such as methylammonium lead halide. They posses less cost and simple fabrication. The efficiency of perovskite-based solar cells has been steadily increasing (more than 20%).
This type of solar cell material is a small molecule dye, such as a ruthenium metalorganic dye, that can absorb a broad range of the visible region of sunlight.
Nanoparticles also known as quantum dots.They have low bandgap and it can be tuned by changing the size of the particle ( such as in CdS, CdSe, and PbS). Pb and Cd are considered toxic, therefore copper indium selenide CIS are being developed.
Perovskites take their name from the mineral, which was first discovered in the Ural mountains of Russia by Gustav Rose in 1839 and is named after Russian mineralogist L. A. Perovski (1792-1856).
The cubic perovskite structure is observed in many compounds featuring a composition ABX3, where 'A' and 'B' are two cations of very different sizes, and X is an anion that bonds to both. The 'A' atoms are larger than the 'B' atoms. In ABO3 structured compounds, A ion is twelvefold coordinated by oxygen (like dodecahedra) and B ion is octahedrally coordinated by oxygen ions.
Oxygen atoms form an FCC-like cell with atoms missing from the corners which are occupied by A atoms.
An important parameters about perovskites is the their Tolerance Factor (t)"which is defined as
Perovskites can also have various combinations of ionic valence such as A2+B4+O4 , BaTiO3, PbTiO3, CaTiO3, SrTiO3 ,A3+B3+O4 , LaAlO3, LaGaO3, BiFeO3 etc.
Arranging the stacked pervoskites on a silicon solar cells improves the efficiency of the solar cells.Perovskite is a crystalline material.It is inexpensive and can be easily produced in the lab. Scientists showed that perovskites are made of lead, iodide and methylammonium that converts sunlight into electricity with an efficiency of 3.8%. Since then researchers had achieved the above 20% efficiency. This result was very impressive.
We can get the large efficiency boost by the combination of two cells of the approximately same energy.
Silicon is just like a rock. If we heat it to a 600 degrees Fahrenheit shine light on it for 25 years. No change will occur.But if we expose pervoskites to light or water, it will be easily degraded. Thus shows that pervoskites solar cells are more stable even for 25 years. It is highlighted by the co-author Michael McGehee, a professor of materials science and engineering at Stanford that in the five to ten years, the efficiency will be reaching nearly 30%. His vision is that someday they will be able to get low-cost tandems that has an efficiency of 25%.
In the coming future research, the scientists are likely to emphasize on the reduction of recombination through strategies such as passivation and reduction of defects. Charge extractions layers are likely to move away from different layers that improves efficiency and stability.
Future research directions for pervoskite solar cells are going to be finding Pb -free light absorbing materials. Protection technologies, in order not to release Pb from the Pb- based pervoskite solar cells, will be an important issue. The most significant potential use of the perovskites in light-emitting diodes and resistive memories.
This idea of research began as a joke on a shining morning. Researchers from the University of California, Los Angeles (UCLA) and Solargiga Energy in China have discovered that caffeine can help make a promising alternative to traditional solar cells and makes more efficient in conversion of light into electricity.
If a human needs coffee to boost their energy, then how these pervoskites gets energy. "Would these pervoskites also need coffee to boost their energy?" Rui Wang and Jingjing Xue discussed.They recalls that caffeine in coffee is an alkaloid compound that contains molecular structures that could interact with the precursors of perovskite materials. Compounds having a particular crystal structure can form the light-harvesting layers between the layers of solar cells. Previously the attempt was done to improve the thermal stability of these solar cells by applying dimethyl sulfoxide between pervoskite layers. This also boost the efficiency and long-term stability. But no one had tried caffeine.
For further investigation, the team began investigating. They added caffeine to the pervoskite layer of 40 solar cells. They uses infrared radiations for identifying the chemical compounds in order to determine that caffeine had been effectively bonded with the materials. On doing further infrared spectroscopy tests they observed that a carbon is bonded to an oxygen group in caffeine that interacts with lead ions in the layer to create a " molecular lock". This locking increased the threshold energy required by the pervoskite film to react and boosting the efficiency from 17 to 20 %. The molecular lock even exists on heating the materials, and this could prevent heat from breaking down the layer. But in order to improve efficiency these pervoskites utilize solar energy, hence researchers do not think it to be useful for other types of solar cells.
Pervoskites are cheaper and more flexible as compared to silicon. These can be easily manufactured and can be fabricated from solution-based precursors. Wang believes that caffeine can be applied in large scale pervoskites solar cells. Caffeine can help the perovskite achieve low defects, high crystallinity, and good stability, he remarked. In order to enhancing stability and efficiency of solar cells, the scientists are further investigating the chemical structure of caffeine and identifying the best protective materials for pervoskites.
This research have discovered that caffeine can lend a helping hand as an alternative to solar energy that can convert light into electricity. This also enables cost-effective renewable energy technology to compete in the market with the silicon solar cells.
In the coming future research, scientists are likely to emphasize on the reduction of recombination through strategies such as passivation and reduction of defects. Charge extractions layers are likely to move away from different layers that improves efficiency and stability.
Future research directions for pervoskite solar cells are going to be finding Pb free light absorbing materials. Protection technologies, in order not to release Pb from the Pb-based pervoskite solar cells, will be an important issue. The most significant potential use of the perovskites in light-emitting diodes and resistive memories.
Caffeine Gives An Energy Boost To Solar Cells. (2019, Dec 16). Retrieved from https://studymoose.com/caffeine-gives-an-energy-boost-to-solar-cells-essay
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