page_title: Amorphous silicon
section_title: Photovoltaic thermal hybrid solar collectors
hierarchical_section_title: Amorphous silicon / Applications / Photovoltaics / Photovoltaic thermal hybrid solar collectors
caption_attribution_description: English: Aerospace Product-Flexible Thin-Film Solar PV-United Solar Ovonic
context_page_description: Amorphous silicon is the non-crystalline form of silicon used for solar cells and thin-film transistors in LCDs.
  Used as semiconductor material for a-Si solar cells, or thin-film silicon solar cells, it is deposited in thin films onto a variety of flexible substrates, such as glass, metal and plastic. Amorphous silicon cells generally feature low efficiency, but are one of the most environmentally friendly photovoltaic technologies, since they do not use any toxic heavy metals such as cadmium or lead.
  As a second-generation thin-film solar cell technology, amorphous silicon was once expected to become a major contributor in the fast-growing worldwide photovoltaic market, but has since lost its significance due to strong competition from conventional crystalline silicon cells and other thin-film technologies such as CdTe and CIGS.
  Amorphous silicon differs from other allotropic variations, such as monocrystalline silicon—a single crystal, and polycrystalline silicon, that consists of small grains, also known as crystallites.
context_section_description: Photovoltaic thermal hybrid solar collectors (PVT), are systems that convert solar radiation into electrical energy and thermal energy. These systems combine a solar cell, which converts electromagnetic radiation (photons) into electricity, with a solar thermal collector, which captures the remaining energy and removes waste heat from the solar PV module. Solar cells suffer from a drop in efficiency with the rise in temperature due to increased resistance. Most such systems can be engineered to carry heat away from the solar cells thereby cooling the cells and thus improving their efficiency by lowering resistance. Although this is an effective method, it causes the thermal component to under-perform compared to a solar thermal collector. Recent research showed that a-Si:H PV with low temperature coefficients allow the PVT to be operated at high temperatures, creating a more symbiotic PVT system and improving performance of the a-Si:H PV by about 10%.
caption: Aerospace product with flexible thin-film solar PV from United Solar Ovonic
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