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Thin film design is a manufacturing technique of depositing very thin layers of on a base or substrate material. The process can be used for paint coatings, electronic parts, or solar cells to create electricity from light. A thin film describes the process of adding very fine amounts of product in repeating layers, not necessarily how thick is the finished product.
Early electronics used heavy and bulky vacuum tubes and other parts to make televisions and electronics in the mid-20th century. In time, semiconductors and solid-state devices became available, allowing electronics to use lightweight, small circuits. Into the 21st century, continuing improvements in electronic circuit design led to devices with smaller sizes and more computing capacity. Thin film design is important for its ability to use small amounts of expensive raw materials to make circuits at relatively low cost.
Despite the concept that thin film design is about the process, not the size of the part, a growing market in the early 21st century was the development of flexible circuits. Rather than having to use rigid circuit boards, developers could now create electronic parts on very thin, flexible plastics. A market that benefited from this improvement was solar electricity.
Solar panels in the early to mid-20th century were heavy, rigid panels made with solid glass and thick layers of electricity-generating materials. In time, thin film design led to rigid panels with much lower weight that reduced installation time and expense. Additionally, thin films allowed solar panels to be placed in portable calculators, radios and cellular phones or chargers at low cost. In the late 20th century, solar cells were first produced on plastic film, allowing the panel to be rolled up for storage or installed as the outer surface of a building or vehicle.
Energy efficiency, a measurement of how much sunlight is converted to electricity, was low in early solar designs. The electricity made from solar panels was typically stored in batteries that had their own efficiency limitations. It was important to maximize the energy efficiency of solar designs, and thin film design allowed efficiencies to rise to above 20 percent in the early 21st century, with additional improvements expected as new materials were tested.
In the 21st century, solar thin films used either a mixture of crystalline and non-crystalline, or amorphous, silicon. Crystalline silicon might be compared to sand, where the molecules have a fixed, regular structure. An amorphous material is like glass, where the molecules are more random with different physical and electrical properties.
At the same time, metals mixtures that could create electricity from light were developed for solar cells. Copper indium gallium selenide (CIGS) and cadmium telluride (CdTe) were two technologies used as an alternative to silicon. These metals, although toxic in some cases, were rigidly fixed in the thin film design, and at the time not considered environmental hazards. In all cases, manufacturers chose a particular design to create the highest efficiency per unit cost, in order to gain market advantage.
Some products can be sprayed similarly to paint onto a glass or film base. Alternating layers of electrically conducting and non-conducting materials can create electronic circuits. Another process for depositing thin films is sputtering, where the material is vaporized and given an electrical charge, where it is attracted to the base material with an opposite charge. Laser light can be used to vaporize materials to be deposited on a substrate. Plasma, a high-energy electrical discharge, can be used to transfer materials in some thin film designs.
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