In the future, decarbonized societies that use internet of things (IoT) devices will become commonplace. But to achieve this, we need to first realize highly efficient and stable sources of renewable energy. Solar cells are considered a promising option, but their electrical contacts suffer from a “tradeoff” relationship between surface passivation and conductivity. Recently, researchers from Japan have developed a new type of electrical contact that can overcome this problem.
The most recent type of commercial photovoltaic cell (solar cell) uses stacked layers of crystalline silicon (c-Si) and an ultrathin layer of silicon oxide (SiOx) to form an electrical contact. The SiOx is used as a “passivating” film—an unreactive layer that improves the performance, reliability, and stability of the device. But that does not mean that simply increasing the thickness of this passivating layer will lead to improved solar cells. SiOx is an electrical insulator and there is a trade-off relationship between passivation and the conductivity of the electrical contact in solar cells.
In a new study, published in ACS Applied Nano Materials, a research team led by Assistant Professor Kazuhiro Gotoh and Professor Noritaka Usami from Nagoya University has developed a novel SiOx layer that simultaneously allows high passivation and improved conductivity. Named NAnocrystalling Transport path in Ultrathin dielectrics for REinforcing passivating contact (NATURE contact), the new electrical contact consists of three-layer structures made up of a layer of silicon nanoparticles sandwiched between two layers of oxygen-rich SiOx. “You can think of a passivating film as a big wall with gates in it. In the NATURE contact, the big wall is the SiOx layer and the gates are Si nanocrystals,” explains Dr. Gotoh.
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