Solar cell with transparent passivate contact achieves 23.99% efficiency

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Researchers from the Jülich Institute for Energy and Climate Research (IEK-5) in Germany claim to have fabricated a prototype of solar cell based on a transparent passivate contact (TPC) with a power conversion efficiency of 23.99%.

The result was confirmed by the CalTeC laboratory of the Institute for Solar Energy Research in Hamelin (ISFH). “This means that the Jülich TPC solar cell still ranks slightly below the best crystalline silicon cells made in laboratories to date,” the scientists said. “But simulations carried out in parallel have shown that efficiencies of more than 26 percent are possible with TPC technology.”

The device passivation was achieved through ultra-thin transparent layers that are claimed to be effective in preventing recombination events. “In this process, negative and positive charge carriers that have already been generated combine and cancel each other out before they could be used for the flow of solar electricity,” the German group explained. “This effect can be countered by special materials that have a special property — passivation.”

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The manufacturing process is based on wet chemical processes, chemical vapor deposition (CVD), and a sputtering technique. The prototype was fabricated with a double layer of tiny pyramid-shaped nanocrystals of silicon carbide and a transparent layer of indium tin oxide which were both deposited on a thin layer of silicon dioxide.

The academics also claim that, on top of providing the desired passivation, the transparent layers reduce the incidence of light and have high electrical conductivity. “No other approach so far combines these three properties — passivation, transparency, conductivity — as well as our new design,” said researcher Kaining Ding, noting that the passivation technology may be easily scaled up for commercial production. “We expect solar cell manufacturers to show great interest in our technology,” he stated.

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