Electrochromic Glass and Its Uses
Electrochromic glass works on the concept of electrochromism which enables it to change from transparent to opaque when an electric voltage is applied across it.
What is this used for?
As the layers tint, they can be used to absorb the heat from the sun and thereby help in keeping the interiors cool during a hot day. During the night, the glass can be turned back to its transparent self.
A typical insulated glass is made up of two layers glass which are separated by an air gap. This helps in sound proofing. Electrochromic glass too works on a similar concept.
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It has 5 thin layers which are about one micron thick sandwiched between the two outer panes of glass. It has two transparent conducting layers of (TC1 and TC2), two electrochromic layer (EC1 and EC2) and an ion conducting layer (IC) which acts as a separator between the two electrochromic layers.
Initially when the window is transparent, the ions reside in the inner most layer (EC2) made of lithium cobalt oxide.
When a small voltage is applied between the transparent layers TC1 and TC2, then the ions move to the outer layer EC1 made of a poly-crystalline tungsten oxide which reflects light causing the glass to tint.
Once the voltage is reversed, the ions move back to the inner most layer causing the glass to become transparent.
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This type of glass commonly finds application in homes but is now being used in automobiles as well. The McLaren 570GT has an electrochromic glass which allows it to shift from transparent to opaque when needed.
OnePlus showed off their concept one phone which used the electrochromic glass to hide the rare cameras and act as a Neutral Density Filter (ND Filter) which allows the user to use a wider aperture in brightly lit environment. This helps in the image not being over exposed by reducing the amount of light entering into the lens while at the same time getting a good bokeh.
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