New approach to trapping sunlight with silicon nanowires

WASHINGTON - Researchers with the Lawrence Berkeley National Laboratory (Berkeley Lab) are developing a new approach, which would use silicon nanowires to better trap sunlight for future renewable green energy equations.

Although there are silicon photovoltaics that can convert sunlight into electricity at impressive 20 percent efficiencies, the cost of this solar power is prohibitive for large-scale use.

And the new approach could substantially reduce these costs.

The researchers have developed a photovoltaic cell, comprising of 36 individual arrays of silicon nanowires featuring radial p-n junctions.

Semiconductor nanowires are one-dimensional strips of materials whose width measures only one-thousandth that of a human hair but whose length may stretch several microns.

“Through the fabrication of thin films from ordered arrays of vertical silicon nanowires we’ve been able to increase the light-trapping in our solar cells by a factor of 73,” said chemist Peidong Yang, who led the research.

“Since the fabrication technique behind this extraordinary light-trapping enhancement is a relatively simple and scalable aqueous chemistry process, we believe our approach represents an economically viable path toward high-efficiency, low-cost thin-film solar cells.

“Typical solar cells are made from very expensive ultrapure single crystal silicon wafers that require about 100 micrometers of thickness to absorb most of the solar light, whereas our radial geometry enables us to effectively trap light with nanowire arrays fabricated from silicon films that are only about eight micrometers thick.

“Furthermore, our approach should in principle allow us to use metallurgical grade or “dirty” silicon rather than the ultrapure silicon crystals now required, which should cut costs even further,” he added.

Yang and his group are able to reduce both the quantity and the quality requirements for silicon by using vertical arrays of nanostructured radial p-n junctions rather than conventional planar p-n junctions.

The study has been published in the journal NANO Letters. (ANI)