Types of Solar Cells and its Applications

A solar cell is an electronic device which directly converts sunlight into electricity. Light shining on the solar cell produces both a current and a voltage to generate electric power. This process requires firstly, a material in which the absorption of light raises an electron to a higher energy state, and secondly, the movement of this higher energy electron from the solar cell into an external circuit. With regard to the development of sustainable energy, such as solar energy, in this article we will Study types of solar cells and their applications.

Quantum Dot Solar Cell
A quantum dot solar cell is a solar cell design that uses quantum dots as the absorbing photovoltaic material. It attempts to replace bulk materials such as silicon, copper indium gallium selenide (CIGS) or CdTe. Quantum dots have bandgaps that are tunable across a wide range of energy levels by changing the dots' size. In bulk materials the bandgap is fixed by the choice of materials.
This property makes quantum dots attractive for multi-junction solar cells, where, a variety of materials are used to improve efficiency by harvesting multiple portions of the solar spectrum.

Quantum dot solar cell working
Large-scale production could use spray-on or roll-printing systems, dramatically reducing module construction costs. Early examples used costly molecular beam epitaxy processes, but less expensive fabrication methods were later developed. These use wet chemistry and subsequent solution processing. Concentrated nanoparticle solutions are stabilized by long hydrocarbon ligands that keep the nanocrystals suspended in solution. To create a solid, these solutions are cast down (clarification needed) and the long stabilizing ligands are replaced with short - chain crosslinkers. Chemically engineering the nanocrystal surface can better passivate the nanocrystals and reduce detrimental trap states that would curtail device performance by means of carrier recombination. This approach produces an efficiency of 7.0%.

Thin Film Solar Cell (TFSC)
A thin-film solar cell (TFSC), also called a thin-film photovoltaic cell (TFPV), is a second generation solar cell that is made by depositing one or more thin layers, or thin film (TF) of photovoltaic material on a substrate, such as glass, plastic or metal. Thin-film solar cells are commercially used in several technologies, including cadmium telluride (CdTe), copper indium gallium diselenide (CIGS), and amorphous and other thin-film silicon (a-Si, TF-Si).

Structure of thin film solar cells
Film thickness varies from a few nanometers (nm) to tens of micrometers (μm), much thinner than thin-film's rival technology, the conventional, first-generation crystalline in most solar PV systems. Despite these enhancements, market-share of thin-film never reached more than 20 percent in the last two decades and has been declining in recent years to about 9 percent of worldwide photovoltaic production in 2013. Other thin- film technologies, that are still in an early stage of ongoing research or with limited commercial availability, are often classified as emerging or third generation photovoltaic cells and include, or ganic, dye-sensitized, and polymer solar cells, as well as quantum dot, copper zinc tin sulfide, nanocrystal, micromorph and perovskite solar cells.
Biohybrid Solar Cell
A biohybrid solar cell is a solar cell made using a combination of organic matter (photosystem I) and inorganic matter. Biohybrid solar cells have been made by a team of researchers at V anderbilt University. The team used the photosystem I (a photoactive protein complex located in the thylakoid membrane) to recreate the natural process of photosynthesis to obtain a greater efficiency in solar electric energy conversion. These biohybrid solar cells are a new type of renewable energy.
Multilayered bio hybrid solar cell
Multiple layers of photosystem I gather photonic energy, convert it into chemical energy and create a current that goes through the solar cell. The cell itself consists of many of the same non-organic materials that are found in other solar cells with the exception of the injected photosystem I complexes which are introduced and gathered for several days in the gold layer. After days the photosystem I are made visible and appear as a thin green film. It is this thin film that helps and improves the energy conversion.
The biohybrid cell however, is still in the research phase. The team from V anderbilt University began conducting research on the photosynthesis when they began to see and focus on the photosystem I protein. After seeing how widely available and efficient the protein was at solar conversion they began to look to incorporate and improve different technologies. The team used spinach as their source for the photosystem I. Thylakoid membranes were isolated and then went into a purification process to separate the photosystem I from the thylakoid membrane. Their research resulted in a greatly improved electrical current (1000 times greater) compared to those previous made by other solar cells. The team has been gathering a group of undergraduate engineers to help build the first prototype of the biohybrid solar cell. The team has also come up with a second design of the protein complex the photosystem II.
Micromorph Cells (Tandem-Cell Using a Si/μc-Si)
Micromorph solar cells are thin film solar cells based on a multijunction - architecture consisting of two solar cells that are stacked on top of each other. While the thin amorphous silicon top solar cell absorbs the blue light, the thicker microcrystalline silicon bottom cell absorbs the red and near-infrared light, allowing this so-called tandem cell to cover a wider range of the solar spectrum.
Schematic micromorph cell structure
"Micromorph" tandem solar cells consisting of a microcrystalline silicon bottom cell and an amorphous silicon top solar cell are considered as one of the most promising new thin-film silicon solar-cell concepts. Their promise lies in the hope of simultaneously achieving high conversion efficiencies at relatively low manufacturing costs. Since the bandgaps of amorphous

Silicon (1.7eV) and microcrystalline
Silicon (1.1eV) are well suited for tandem solar cells, the Shockley - Queisser limit of this solar cell allows conversion efficiencies of over 30%.
In reality this limit can not be reached and typical stable efficiencies are about 9% (world record 11.7%). That is well over the stable efficiencies of single junction thin film silicon solar cells which are around 6%. One reason of the low costs of silicon thin film solar cells is its very low thickness (2 μm) compared to silicon wafer (200 μm). In the red and infrared wavelength range 2 μm of silicon are not enough to absorb all light and therefore Light trapping is needed.

Some of Applications of solar energy
Power plants: In conventional power plants non-renewable energy sources are used to boil water and form stream so that turbines can rotate and water to produce electricity. But with application of solar renewable energy heat of sun can boil that water to create steam and rotate turbines. To convert sunlight into electricity solar panels, photoelectric technologies and thermoelectric technologies are used.
Residential appliances: Homes Use of solar energy is increasing in homes as well. Residential appliances can easily use electricity generated through solar power. Besides this solar energy is running solar heater to supply hot water in homes. Through photovoltaic cell installed on the roof of the house energy is captured and stored on batteries to use throughout the day at homes for different purposes. In this ways expenditure on energy is cutting down by home users.
Commercial use: On roofs of different buildings we can find glass PV modules or any other kind of solar panel. These solar panels are used there to supply electricity to different offices or other parts of building in a reliable manner. These solar panels collect solar energy from sun, convert it into electricity and allow offices to use their own electrical power for different purposes.
Ventilation system: At many places solar energy is used for ventilation purposes. It helps in running bath fans, floor fans, and ceiling fans in buildings. Fans run almost every time in a building to control moisture, and smell and in homes to take heat out of the kitchen. It can add heavy amount on the utility bills, to cut down these bills solar energy is used for ventilation purposes.