Applications of Transparent Solar Cells
By Olivia Hakan
Solar cells are not a new invention; the technology has been around for decades. However, even though most people know what solar cells are and what they do, many cannot explain how they work. Simply put, a solar cell is a device that converts light into electricity. Some materials have the ability to absorb photons of light and release electrons which are then captured and turned into an electric current that can then be used as electricity (Knier). Solar cells are typically made of a positive and negative electrode, with a semiconducting material in between. This semiconductor is made of positive (p) and negative (n) type materials. When light hits the cell, electrons are displaced from the p-type portion of the semiconductor creating a positively charged, “hole,” an electron pair, called an exciton. This exciton diffuses towards the n-type portion of the material and the charges separate. This forms an electric current between the electrodes which is used as energy and can be stored or used to power things (Knier).
With the capabilities we have today, scientists are finally able to expand on the longstanding potential of solar technology. There have been many developments in this rapidly developing field, but one of the most exciting possibilities is using see-through solar cells as windows in buildings. Though most solar cell materials give windows a red-brown tint, Richard Lunt’s research group in Michigan has created a solar cell that absorbs exclusively ultraviolet and infrared light, leaving the window completely clear (Service, 2018). These transparent solar cells are made from organic molecules called perovskites. Solar cells are typically silicon-based because of their high efficiency of up to 25%; the theoretical efficiency limit for a solar cell is 33.7%.
However, organic molecules are becoming more widely used due to their low price, easy synthesis, and moldability. And, with the increased research in this area, the efficiencies of organic-based solar cells are quickly closing in on those of silicon. Lunt’s group currently has reported the synthesis of transparent UV and IR absorbing solar cells with efficiencies of 5%. Though this is quite low in terms of typically manufactured solar cells, the group says that they have the potential for efficiencies of up to 20%, which would almost match market values (Service, 2018).
Transparent solar cells have the potential for application in a multitude of places. However, the location with the most significant impact would by far be in construction. There are between 5 and 7 million billion square meters of glass window surface in the US and Buildings account for 75% of electricity use, and 40% globally (Henion). Using transparent solar cells in windows would allow them to reduce their energy consumption dramatically. Even at just single-digit efficiency, if widely used, this would be a revolutionary product. With 5% efficiency, using solar cell windows, buildings could power their air lighting and air conditioning renewably and in-house (Service, 2018). At 20%, there may even be excess to donate to the rest of the grid. With the ever-increasing threat of climate change many things need to be done to minimize damage and help protect our people. Making the switch to renewable energy is one of the most promising ways to begin doing this, and why not utilize the space we have already built on to help us achieve this.
Henion, A. (n.d.). Transparent Solar Technology 'Wave of the Future'. Retrieved from https://research.msu.edu/transparent-solar-technology-wave-of-the-future/
Knier, G. (n.d.). How do Photovoltaics Work? Retrieved from https://science.nasa.gov/science-news/science-at-nasa/2002/solarcells
Lunt, R., Bulovic V. (2011). Transparent, near-infrared organic photovoltaic solar cells for window and energy-scavenging applications. Appl. Phys. Lett. 98, 113305. doi: https://doi.org/10.1063/1.3567516
Service, R. F. (2018). See-through solar cells could power offices. Science,360 (6396), 1386-1386. doi:10.1126/science.360.6396.1386