Many people may notice that the solar panels lying on the roofs of residents are subdivided into small pieces, and these grid lines are actually the metal conductors of solar cells. Although they exist for the transmission of electrical energy, excessive "footprint" compromises the solar energy absorption/conversion efficiency per unit. But now, researchers at Stanford University have found a way to allow them to give way to the underlying semiconductors, using "concealed contact" technology.
Through the grey silicon nanopillars of the gold contact layer, the structure can achieve invisible/concealed metal contacts on solar panels.
Although the contact portion of the upper metal is very thin, it still occupies 10% of the surface of the solar panel. What the Stanford researchers did was find a way to squeeze the space between the underlying semiconductor and the metal so that it was "nearly invisible" to the incident light.
To achieve this, the researchers placed a 16nm thick gold thin film conductive metal layer on the silicon wafer. Although the gold layer is almost a solid one from the naked eye, it is actually covered with a full row of square holes, covering only 65% ​​of the silicon surface, and an average of 50% of incident light.
After the silicon gold structure is treated with hydrofluoric acid and hydrogen peroxide, the gold layer will be trapped on the silicon substrate, and the silicon nanocolumns will pass through the gold layer film. The team called the chemical process "convex contacts," and shiny gold turned dark red in seconds, while the height of the silicon column grew to 330 nm.
Graduate students Vijay Narasimhan, Ruby Lai, and Thomas Hymel have discovered how to make metal contacts on solar panels "invisible" under incident light.
The main author of the study, Vijay Narasimhan, compared the nanosilicon column to the filter pan in the kitchen sink:
Once the nano-silicon pillars are initially highlighted, the light near the metal grid is funneled to the underlying silicon substrate. When you turn on the tap, not all the water will flow into the loophole of the filter.
But if you put a small funnel on top of each loophole, all the water will naturally flow through the coefficients, and that's what the structure we built has to do—the nanosilicon column acts as a loophole, catching light And introduce it into the metal grid of the silicon substrate.
After a series of simulations and experiments, the team optimised this design so that nearly two-thirds of the surface was covered by metal and the reflection loss was only 3%.
Narisimhan said: Compared with traditional solar technology, building new solar cells can significantly increase the efficiency of the panel by 20% to 22%.
Although the initial breakthrough was achieved through gold conductors, Ruby Lai, co-author of the research report, said that the nano-pillar structure is also applicable to other materials such as silver, platinum, and nickel.
In addition, the team said that this technology can also be used on other semiconductor materials to open up more potential for photoelectric sensors, LEDs, displays, and transparent battery lamp technologies.
The team was planning to put the new design on a solar cell under real-world conditions for work testing, and it was described in the above video.
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