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Nanocone-Tips Take Solar Cell Efficiency to Next Level

May. 2 2011 - 3:58 pm |

By WILLIAM PENTLAND

Solar cells designed with 3-D nanocone tips can boost the light-to-power conversion efficiency of photovoltaics by a whopping 80%, according to research conducted at the U.S. Department of Energy’s Oak Ridge National Laboratory.

The new solar structure consists of n-type nanocones made of zinc oxide surrounded by a p-type semiconductor matrix made of polycrystalline cadmium telluride.  All engineering mumbo-jumbo aside, the resulting nanocone-tipped cells converted light-to-power with efficiency of 3.2% compared to 1.8% efficiency of conventional planar structure of the same materials.

The new technology solves significant performance problems resulting from the inefficient migration of electron charges associated with solar photons. These charges are commonly trapped by defects in bulk materials and their interfaces.  

“To solve the entrapment problems that reduce solar cell efficiency, we created a nanocone-based solar cell, invented methods to synthesize these cells and demonstrated improved charge collection efficiency,” said Jun Xu, a member of ORNL’s Chemical Sciences Division. “We designed the three-dimensional structure to provide an intrinsic electric field distribution that promotes efficient charge transport and high efficiency in converting energy from sunlight into electricity.”

The research underlying this technology was presented at this year’s Institute of Electrical and Electronics Engineers photovoltaic specialist conference and will be published in the IEEE Proceedings.

“The important concept behind our invention is that the nanocone shape generates a high electric field in the vicinity of the tip junction, effectively separating, injecting and collecting minority carriers, resulting in a higher efficiency than that of a conventional planar cell made with the same materials,” Xu said.