Solar panels have become dramatically more efficient over the last few decades. In 1954, the first commercially viable panels from Bell Labs had only 6 percent efficiency. Since then, panel efficiency has surged, reaching one milestone after another; for example, in January 2016 the National Renewable Energy Laboratory and the Swiss Center for Electronics and Microtechnology nearly reached the 30 percent mark.
Many manufacturing improvements have contributed to this long-term trend toward more useful solar technologies. An important recent development has been the at-scale use of black silicon to increase sunlight absorption.
What is black silicon?
If you’ve ever worn an all-black article of clothing during a particularly hot, sunny day, then you have probably experienced firsthand how darker materials are magnets for heat: Compared to lighter colors, black clothes absorb more light. The same holds for solar panels.
However, there’s an important distinction: Black silicon becomes “black” through a specific etching process, rather than the coloration associated with clothing production. The procedure entails the use of high-energy laser pulses, oxidizers, hydrofluoric acid and/or metal-assisted wet etching to create nanotextures on the surface of a silicon wafer. In contrast, traditional crystalline silicon has a completely smooth veneer.
Why are these nanotextures advantageous?
The undulated surfaces of black silicon allow it to absorb sunlight throughout the day. More specifically, crystalline silicon only has optimal absorption when the sun is at its peak in the sky, since panel efficiency is best when photons reach the panel perpendicularly; black silicon can efficiently pick up energy from many angles and better capture reflected and shorter wavelength light, too, thanks to its texturing.
There is considerable variance in black silicon designs, with choices related to balancing reflection and efficiency particularly key to optimizing panel efficiency. Photons can get trapped within the numerous peaks and valleys of a black panel and accordingly become unusable for energy conversion.
What other benefits can black silicon deliver?
Because black silicon does not need anti-reflective coating, it can usually be manufactured at lower cost than panels that do require it. There are also many experimental use cases for black silicon that could enhance its usability. For example, the etching could be done as a single-sided process with a smooth reverse side ideal for some specific high-efficiency layouts. Passivation – i.e., the depositing of an outer layer of a compound such as aluminum oxide on the black silicon – is another way to boost efficiency by reducing the number of trapping areas.
What does black silicon mean for solar viability in the long run?
The design advantages and diverse use cases of black silicon panels are best understood as one innovation among many that have pushed solar panel technology into the mainstream. Swanson’s Law, which holds that solar photovoltaic cell prices decline 20 percent each time global installed capacity doubles, has also helped to bring solar to larger audiences across the globe.
Gains in both efficiency and affordability are critical to the long-term sustainability of the solar market. Trina Solar has been at the forefront of creating innovative black silicon solar solutions that combine excellent efficiency with aesthetically pleasing designs. Products such as deep black monocrystalline cells can bring considerable power to small spaces on rooftops. Moreover, the proven real-world reliability of Trina’s offerings, along with their support and warranties, ensure the best possible return on investment for customers. Learn more by visiting our products page or contacting us directly today.
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