American scientists have succeeded in developing a photoelectrochemical cell that can capture excess photon energy which is otherwise lost to heat generation, and generate solar fuels from it.

The US Department of Energy's National Renewable Energy Laboratory (NREL) scientists could extend the peak external quantum efficiency for hydrogen generation to 114% during their experiment. This, they could do so by using quantum dots (QD) and the Multiple Exciton Generation (MEG) process.

The findings from the experiment could lead to considerable increase in hydrogen production from sunlight by using the proof-of-principle cell to divide water at an increased efficiency and reduced cost than what is offered by the present photoelectrochemical methods.

The research findings are included in the paper dubbed as Multiple exciton generation for photoelectrochemical hydrogen evolution reactions with quantum yields exceeding 100%. The paper has been jointly authored by Matthew Beard, Yong Yan, and Ryan Crisp among others.

In 2011, Beard along with other NREL scientists published a paper outlining how MEG process enabled a solar cell to cross 100% quantum efficiency by generating more electrons in the electrical current compared to the number of photons making their way into the solar cell.

Beard said: "The major difference here is that we captured that MEG enhancement in a chemical bond rather than just in the electrical current.

"We demonstrated that the same process that produces extra current in a solar cell can also be applied to produce extra chemical reactions or stored energy in chemical bonds."

For their experiment to capture surplus photon energy, the NREL researchers invented a cell derived from a lead sulfide (PbS) QD photoanode.

The photoanode comprises a layer of PbS quantum dots found on top of a titanium dioxide/fluorine-doped tin oxide dielectric stack.

The subsequent chemical reaction caused by the surplus electrons showed a new direction in discovering high-efficiency approaches for solar fuels.

Image: A lead sulfide quantum dot solar cell developed by NREL researchers. Photo: courtesy of Dennis Schroeder/NREL.