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New solar cell technology greatly boosts efficiency

Date:
April 29, 2011
Source:
DOE/Oak Ridge National Laboratory
Summary:
With the creation of a 3-D nanocone-based solar cell platform, scientists have boosted the light-to-power conversion efficiency of photovoltaics by nearly 80 percent.

Nanocone-based solar cell consisting of n-type nanocones, p-type matrix, transparent conductive oxide (TCO) and glass substrate.
Credit: Image courtesy of DOE/Oak Ridge National Laboratory

With the creation of a 3-D nanocone-based solar cell platform, a team led by Oak Ridge National Laboratory's Jun Xu has boosted the light-to-power conversion efficiency of photovoltaics by nearly 80 percent.

The technology substantially overcomes the problem of poor transport of charges generated by solar photons. These charges -- negative electrons and positive holes -- typically become trapped by defects in bulk materials and their interfaces and degrade performance.

"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 Xu, a member of ORNL's Chemical Sciences Division.

The new solar structure consists of n-type nanocones surrounded by a p-type semiconductor. The n-type nanoncones are made of zinc oxide and serve as the junction framework and the electron conductor. The p-type matrix is made of polycrystalline cadmium telluride and serves as the primary photon absorber medium and hole conductor.

With this approach at the laboratory scale, Xu and colleagues were able to obtain a light-to-power conversion efficiency of 3.2 percent compared to 1.8 percent efficiency of conventional planar structure of the same materials.

"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," Xu said.

Key features of the solar material include its unique electric field distribution that achieves efficient charge transport; the synthesis of nanocones using inexpensive proprietary methods; and the minimization of defects and voids in semiconductors. The latter provides enhanced electric and optical properties for conversion of solar photons to electricity.

Because of efficient charge transport, the new solar cell can tolerate defective materials and reduce cost in fabricating next-generation solar cells.

"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.

Research that forms the foundation of this technology was accepted by this year's Institute of Electrical and Electronics Engineers photovoltaic specialist conference and will be published in the IEEE Proceedings. The papers are titled "Efficient Charge Transport in Nanocone Tip-Film Solar Cells" and "Nanojunction solar cells based on polycrystalline CdTe films grown on ZnO nanocones."

The research was supported by the Laboratory Directed Research and Development program and the Department of Energy's Office of Nonproliferation Research and Engineering.

Other contributors to this technology are Sang Hyun Lee, X-G Zhang, Chad Parish, Barton Smith, Yongning He, Chad Duty and Ho Nyung Lee.


Story Source:

The above story is based on materials provided by DOE/Oak Ridge National Laboratory. Note: Materials may be edited for content and length.


Cite This Page:

DOE/Oak Ridge National Laboratory. "New solar cell technology greatly boosts efficiency." ScienceDaily. ScienceDaily, 29 April 2011. <www.sciencedaily.com/releases/2011/04/110429121853.htm>.
DOE/Oak Ridge National Laboratory. (2011, April 29). New solar cell technology greatly boosts efficiency. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2011/04/110429121853.htm
DOE/Oak Ridge National Laboratory. "New solar cell technology greatly boosts efficiency." ScienceDaily. www.sciencedaily.com/releases/2011/04/110429121853.htm (accessed July 31, 2014).

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