‘Honeycomb graphene’ promise for cheaper solar cells

A new, inexpensive material could replace the platinum in solar cells without degrading their efficiency, claims Yun Hang Hu, a researcher at Michigan Technological University.

Dye-sensitised solar cells are thin, flexible, easy to make and very good at turning sunlight into electricity but the platinum contained within them is expensive at $1,500 an ounce.

Hu’s replacement material is a 3D version of graphene that possesses a honeycomb-like structure.

To synthesise the material Hu and colleagues combined lithium oxide with carbon monoxide to form lithium carbonate (Li2CO3) and the honeycomb graphene. The Li2CO3 helps shape the graphene sheets and isolates them from each other, preventing the formation of graphite.

Furthermore, the Li2CO3 particles can be easily removed from 3D honeycomb-structured graphene by an acid.

According to MTU, the researchers determined that the 3D honeycomb graphene had excellent conductivity and high catalytic activity, raising the possibility that it could be used for energy storage and conversion. They replaced the platinum counter electrode in a dye-sensitised solar cell with one made of the 3D honeycomb graphene. Then they put the solar cell in the sunshine and measured its output.

The cell with the 3D graphene counter electrode converted 7.8 per cent of the sun’s energy into electricity, nearly as much as the conventional solar cell using platinum (eight per cent).

Synthesising the 3D honeycomb graphene is neither expensive nor difficult, Hu said in a statement, and making it into a counter electrode posed no special challenges.

A field emission scanning electron microscopy (FESEM) image of 3D honeycomb-structured graphene. The material can replace platinum in dye-sensitised solar cells with virtually no loss of generating capacity
A field emission scanning electron microscopy (FESEM) image of 3D honeycomb-structured graphene. The material can replace platinum in dye-sensitised solar cells with virtually no loss of generating capacity

An article describing the work, 3D Honeycomb-Like Structured Graphene and Its High Efficiency as a Counter-Electrode Catalyst for Dye-Sensitised Solar Cells, has been co-authored by Hu, the Charles and Caroll McArthur Professor of Materials Science and Engineering at Michigan Technological University, Michigan Tech graduate student Hui Wang, Franklin Tao of the University of Notre Dame, Dario J. Stacchiola of Brookhaven National Laboratory and Kai Sun of the University of Michigan.

It has been published in the journal Angewandte Chemie, International Edition.