Technology that embeds silicon nanoparticles into efficient luminescent solar concentrators (LSCs) has been developed. The LSCs are the key element of windows that can efficiently collect solar energy. When light shines through the surface, the useful frequencies of light are trapped inside and concentrated to the edges, where small solar cells can be put in place to capture the energy.

While most of the light concentrated to the edge of the silicon-based LSC is actually invisible, the concentration effect can be seen by the naked eye when the slab is illuminated by a black light, which is composed of mostly ultraviolet wavelengths. (Uwe Kortshagen, College of Science and Engineering)

Photovoltaic windows have the potential to largely increase the surface of buildings suitable for energy generation without impacting their aesthetics — a crucial aspect, especially in metropolitan areas. LSC-based photovoltaic windows do not require any bulky structure to be applied onto their surface, and since the photovoltaic cells are hidden in the window frame, they blend invisibly into the built environment.

Until recently, the best results for achieving the LSCs had involved relatively complex nanostructures based either on potentially toxic elements such as cadmium or lead, or on rare substances like indium, which is already massively utilized for other technologies. Silicon is abundant in the environment and non-toxic, and also works more efficiently by absorbing light at different wavelengths than it emits. Silicon, in its conventional bulk form, however, does not emit light or luminesce.

The dimension of silicon crystals was decreased to a few nanometers. At this size, silicon’s properties change, and it becomes an efficient light emitter, with the important property not to re-absorb its own luminescence. The optical features of silicon nanoparticles and their nearly perfect compatibility with the industrial process for producing the polymer LSCs create a clear path to developing efficient photovoltaic windows that can capture more than 5 percent of the Sun’s energy at low cost.

The silicon nanoparticles are produced in a process using a plasma reactor, and are formed into a powder. Each particle is made up of less than 2,000 silicon atoms. The powder is turned into an ink-like solution, and then embedded into a polymer, either forming a sheet of flexible plastic material or coating a surface with a thin film.

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