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Groundbreaking transparent solar cells generate power 1000x more efficiently

[Sept 20, 2022: Public Relations, Tohoku University]

An optical image of a highly-transparent solar cell fabricated with a 2D atomic sheet. (CREDIT: Toshiaki Kato)

Solar panels often get a bad rap for spoiling the appearance of homes and businesses. Yet, this may be about to change.

A research group has fabricated a highly transparent solar cell with a 2D atomic sheet. These near-invisible solar cells achieved an average visible transparency of 79%, meaning they can, in theory, be placed everywhere - building windows, the front panel of cars, and even human skin.


Scientists have long sought to develop transparent solar cells, but the suitable materials have not existed thus far.

To make the solar cell, the team controlled the contact barriers between indium tin oxide (ITO), one of the most widely used transparent conducting oxides, and a monolayer tungsten disulfide.


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They coated various thin metals onto the ITO and inserted a thin layer of Tungsten Oxide between the coated ITO and the tungsten disulfide.

"The way in which we formed the solar cell resulted in a power conversion efficiency over 1000 times that of a device using a normal ITO electrode," pointed out Toshiaki Kato, corresponding author of the paper and associate professor at Tohoku University's Graduate School of Engineering.


The group's efforts did not stop there. They also explored how their solar cell can be expanded for use in an actual solar panel.

Highly Transparent Solar Cell with 2D Atomic Sheet Successfully Fabricated. (CREDIT: Toshiaki Kato)

“It was found that the aspect ratio […] [of the] device should be lower than the critical value of approximately 36,” the paper explains. “By further scaling up the device size by considering an optimal series–parallel connection structure, an extremely high transparency of 79% could be realized, with PT reaching up to 420 pW [picowatts].”


"We discovered the appropriate design modifications needed to avoid an unexpected voltage drop that accompanies increasing the device area," said Kato.

(a) Schematic illustration of device structure and ideal optimal band structure for the transparent Schottky solar cell. (b) Images of samples for WF and AVT measurement. ITO was sputtered on quartz substrate and a thin metal film was coated on the top of ITO. (c) Transparency spectra of quartz, ITO/quartz, and Mx/ITO on quartz (Mx = Ni1, Ni5, Fe1, Fe2, Al1, Al5, Cu1, Ag1, Au1, and Au5). (d) Plot of WF for Mx/ITO measured by PYS. Inset in (d) shows typical photoemission features of Ni1/ITO and fitting curve to obtain the WF. (e) Scatters of transparency and work function of tested Mx/ITO. (CREDIT: Scientific Reports)

“This is the highest value within a TMD based solar cell with a few layers,” the paper concludes. “These findings can contribute to the study of TMD-based NISCs from fundamentals to truly industrialized stages.”


Details of their research were published in the journal Scientific Reports.

For more science and technology stories check out our New Discoveries section at The Brighter Side of News.


Note: Materials provided above by Tohoku University. Content may be edited for style and length.


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