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Thin film photovoltaics comprise a photovoltaic technology that typically uses thin substrates of materials, such as metals or plastics, instead of glass plates. Films of different materials are then layered on these substrates to create solar power cells. Photovoltaic cells of this type are not only thin, but light and flexible.
Also called solar film, thin-film photovoltaics were developed primarily to integrate solar power systems into the construction of new and older buildings. The reactive cells in the film are created by depositing thin layers of a photoreactive material, often only several nanometers thick, onto a thin substrate, or base. Other photovoltaic technologies create solar cells by using a crystalline silicon substrate, which is in essence a plate of heavy glass.
Despite the differences in the substrate materials used, thin film photovoltaics function on the same basic principles as do standard solar cells. When sunlight strikes a piece of silicon, it excites the electrons in the material. If conducting layers of opposing charges are placed above and below the silicon, the excited electrons will move toward one side of the silicon, creating a voltaic imbalance and subsequent electrical charge as they do. Primarily, the difference between standard and thin film photovoltaics is that the silicon layer is not in the form of a plate of glass, but a thin flexible silicon layer deposited on a thin, light, and flexible substrate material.
The most significant advantage of thin film photovoltaics is that the cells are light enough to apply to the roofs of existing buildings. Regular solar cells are so heavy and delicate that they require a supporting structure to bear their weight and hold them so that they will not flex and shatter. Often, this involves redesigning and rebuilding the entire roof structure so that it can bear the additional weight of the cells and the substantial structure needed to hold the cells.
Installing thin film photovoltaics often involves little more effort than laying the film down on the existing roof and securing it with screws or other simple fasteners. In most cases, the existing roof structure is already capable of bearing the weight of the solar film and requires no additional reinforcement. Additionally, using this technology in new constructions often requires no significant cost-of-building increases to make the best use of the cells.
While they are cheaper to install, thin film solar cells are typically less efficient in generating a given amount of power per square meter than their crystalline brethren. Still, many other significant financial reasons make thin film photovoltaics worth considering. These include lower purchase price, lower production cost per watt generated, and possible installation in many places where standard photovoltaic cells could not be installed.