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A solar cell, also known as a photovoltaic cell (PV cell), is an electronic device that converts the energy of light directly into electricity by means of the photovoltaic effect. [1] It is a form of photoelectric cell, a device whose electrical characteristics (such as current, voltage, or resistance) vary when it is exposed to light.
A single-nanocrystal (channel) architecture in which an array of single particles between the electrodes, each separated by ~1 exciton diffusion length, was proposed to improve the device efficiency [3] and research on this type of solar cell is being conducted by groups at Stanford, Berkeley and the University of Tokyo.
However, the solar frequency spectrum approximates a black body spectrum at about 5,800 K, [1] and as such, much of the solar radiation reaching the Earth is composed of photons with energies greater than the band gap of silicon (1.12eV), which is near to the ideal value for a terrestrial solar cell (1.4eV).
A cross-sectional schematic of the layers of a bifacial silicon heterojunction solar cell An energy band diagram showing energy levels of layers in a typical SHJ solar cell A "front-junction" heterojunction solar cell is composed of a p–i–n–i–n -doped stack of silicon layers; the middle being an n -type crystalline silicon wafer and the ...
A basic thermophotovoltaic system consists of a hot object emitting thermal radiation and a photovoltaic cell similar to a solar cell but tuned to the spectrum being emitted from the hot object. [1] As TPV systems generally work at lower temperatures than solar cells, their efficiencies tend to be low.
The theoretical performance of a solar cell was first studied in depth in the 1960s, and is today known as the Shockley–Queisser limit. The limit describes several loss mechanisms that are inherent to any solar cell design. The first are the losses due to blackbody radiation, a loss mechanism that affects any material object above absolute zero.
The retina (from Latin rete 'net'; pl. retinae or retinas) is the innermost, light-sensitive layer of tissue of the eye of most vertebrates and some molluscs.The optics of the eye create a focused two-dimensional image of the visual world on the retina, which then processes that image within the retina and sends nerve impulses along the optic nerve to the visual cortex to create visual perception.
White cells are larger than red blood cells and can be larger than the diameter of a capillary, so must deform to fit. As a large, deformed white blood cell goes through a capillary, a space opens up in front of it and red blood cells pile up behind. This makes the dots of light appear slightly elongated with dark tails.