Recently, researchers at the National Renewable Energy Laboratory (NREL) of the U.S. Department of energy have developed windows that can automatically change color when the sun is heated to keep buildings cool - most importantly, they are also solar cells.

The study was published in the journal Nature communication.

Discolored glass has been around for a long time and is enlarged to the size of the window. At the same time, transparent (or translucent) solar cells are becoming more and more efficient and can also be installed on windows.


In this new study, researchers at the National Renewable Energy Laboratory (NREL) of the U.S. Department of energy combined the two technologies into one window. What they call "thermochromic photovoltaic" technology can switch colors when heated by sunlight to block glare and reduce the need for cooling, and also begin to collect energy from these lights.

The window is made of a perovskite film, a new solar cell material, sandwiched between two pieces of glass and injected with solvent vapor in the gap. When the humidity is low, the perovskite film remains transparent, so that the window can transmit light normally. However, at a certain temperature, the steam will rearrange the perovskite crystals, first in chains, then in sheets, and then in cubes. Each new shape will change the color, block the light to varying degrees, and reduce the temperature of the room.


When the glass temperature reaches 35 ° C to 46 ° C, the window can switch between several different colors, from transparent to yellow, orange, red and brown, in about 7 seconds. This is a considerable improvement over the prototype developed by the NREL team in the early stage. When the temperature of the early prototype product reaches 65.5 ° C to 79.4 ° C, it can only be switched between transparent and a red brown color, and it takes 3 minutes to complete.


The team said that a prototype window using the new technology could be developed within a year.