New solar window tech with 2.1% efficiency


A group of scientists from South Korea's Incheon National University has developed a low-cost transparent solar cell that, it is claimed, is able to operate as a self-powered photodetector and a power generator.

The fully transparent solar cell is based on a titanium dioxide (TiO2) layer used as a UV light absorber and a Nickel(II) oxide (NiO) layer deposited for high transmittance for visible light. “The p-type semiconductor NiO serves as the heterojunction counterpart to n-type TiO2,” the researchers explained.

The device was built with a glass substrate, a fluorine-doped tin oxide (FTO) film – on top of which the two layers were deposited – and a coating of silver nanowire. “The FTO and silver nanowires (AgNWs) serve as the bottom and the top electrodes for collecting photo-generated carriers, respectively,” the Korean group specified, adding that the p-n heterostructure-based TiO2 can also separate the photogenerated charges by the internal electric field at junction interface, resulting in self-powered operation.

The measurements taken by the scientists showed that the integrated PV device is able to produce electric power with a conversion efficiency of 2.1%, with more than 57% of visible light being transmitted through the cell's layers. “By UV illumination, the transparent solar cell generated power to move a motor (0.2 V and 10 mA),” they specified. “This clearly suggests the transparent solar cell would serve as an invisible power generator.”

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The low-cost cell may be suitable for various applications in many electronic devices. “While this innovative solar cell is still very much in its infancy, our results strongly suggest that further improvement is possible for transparent photovoltaics by optimizing the cell's optical and electrical properties,” said research co-author Joondong Kim.

The solar cell was described in the study Transparent photovoltaic cells and self-powered photodetectors by TiO2/NiO heterojunction, published in the Journal of Power Sources.

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