Author: Sathish Marimuthu, Research Scholar, VIT Vellore. (02/02/2023)
Imagine a world where the glass on our windows, phones, car sunroofs, and office building glass roofs could be used to generate electricity. Thanks to a new emerging photovoltaic technology, transparent solar panels, which sound like a far-off dream, are getting closer to becoming a reality.
But there is a question that comes to our minds... Is it feasible to develop transparent solar cells...?
The answer is yes. Scientists are now interested in transparent solar technologies because they can be used in many different ways in our everyday lives. In some countries, these things are already done with semi-transparent solar cells. In others, they won't be done for a long time from now, when their efficiency and stability have improved.
Two different extremes...
Transparency is a physical property of a material that allows light to pass through, but the concept of solar cells is to utilise the photonic energy and convert it to electricity. These are two different extremes, which makes it hard to encompass both features in one material.
The Key Solution
To retain a decent level of efficiency, most studies concentrate on developing thin layers to achieve some degree of transparency and absorb the visible spectrum. This often results in cells with a transparency of less than 30%.
But there is another route to achieving transparency in solar cells: changing the molecules of the dye to absorb ultraviolet and near-infrared (NIR) wavelengths (650–850 nm), instead of focusing on the active layer's thickness to achieve a transparent solar cell. A heterojunction organic PV (OPV) is transparent to visible light with a transmission of more than 65% and will absorb in the near-infrared spectrum.
Radiant energy over the solar spectrum
Most photovoltaic (PV) technologies are opaque to maximize visible light absorption.
A selective near-infrared sensitizer based on a polymethine cyanine structure (VG20-Cx) to render dye-sensitized solar cells (DSSCs) fully transparent and colourless.
In 2021 Naim et.al, demonstrated the selective NIR-DSSC can display 3.1% power conversion efficiency. Up to 76% average visible transmittance(AVT) [2].
Does the efficiency of TSCs provide enough power for the future?
The present efficiency of fully transparent solar panels is about 1%, with a potential of 5%. In comparison to conventional solar panels' average efficiency of 15%, efficiencies of 5% and 7.2% for totally and partially transparent panels, respectively, are still extremely low.
However, solar panel efficiency does not imply everything. In reality, all this means is that the panel with the lower efficiency will need to have a bigger surface area than the panel with the higher efficiency to generate the same amount of power. The lower efficiency of transparent solar panels, which may be incorporated into the windows of buildings, implies that the lower efficiency is more than compensated for by the potential job market.
Conclusion
There is still a long way to go before transparent solar panels become reality, but if the advances discussed in this article can be scaled and manufactured more inexpensively, then the far-away goal of a "solar-powered future" and the concept of "zero energy buildings" is not so far away.
References.
[1] Lunt, R. R., & Bulovic, V. (2011). Transparent, near-infrared organic photovoltaic solar cells for window and energy-scavenging applications. Applied Physics Letters, 98(11), 61.
[2] Naim, W., Novelli, V., Nikolinakos, I., Barbero, N., Dzeba, I., Grifoni, F., ... & Sauvage, F. (2021). Transparent and Colorless Dye-Sensitized Solar Cells Exceeding 75% Average Visible Transmittance. Jacs Au, 1(4), 409-426.
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