Tungsten diselenide promises flexible ultrathin semi-transparent solar cells

Technology News |
By eeNews Europe

Although regarded as one of the most promising materials in electronics graphene is not well suited for building solar cells which is why the Vienna University of Technology research team started to look for other materials similar to graphene that can arranged in ultrathin layers, but exhibit better electronic properties.

“The electronic states in graphene are not very practical for creating photovoltaics,” said Thomas Mueller. Therefore, he and his team started to look for other materials, which, similarly to graphene, can arranged in ultrathin layers, but have even better electronic properties.

Tungsten diselenide

The material of choice was tungsten diselenide which consists of one layer of tungsten atoms that are connected by selenium atoms above and below the tungsten plane. The material absorbs light, much like graphene, but in tungsten diselenide (WSe2), this light can be used to create electrical power.

Indeed the layer is so thin that 95% of the light just passes through – but a tenth of the remaining five percent, which are absorbed by the material, are converted into electrical power. Therefore, the internal efficiency is relatively high. A larger portion of the incident light can be used if several of the ultrathin layers are stacked on top of each other – but sometimes the high transparency can be a useful side effect.

“We are envisioning solar cell layers on glass facades, which let part of the light into the building while at the same time creating electricity,” said Mueller.

Standard solar cells, which are mostly made of silicon, are rather bulky and inflexible. Organic materials are also used for opto-electronic applications, but they age rather quickly. “A big advantage of two-dimensional structures of single atomic layers is their crystallinity. Crystal structures lend stability,” explained Mueller.

Microscope photograph of WSe2-samples, connected to electrodes

The results of the experiments at the Vienna University of Technology have now been published in the journal ‘Nature Nanotechnology’.

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