To force non-matching items together, yield better solar cells

ScienceDaily (Sept. 8, 2010) - in what could be a step of to higher efficiency solar cells, an international team to explain the most common model the behavior of a unique class of materials, including the University of Michigan professors that high matching alloy gave invalid.

High mismatched alloys that are combinations of elements, which of course is mixed with conventional crystal growth Techniken.Professor Rachel Goldman compares you to some extent to homogenized milk, still in an experimental stage of development where the high fat cream and low-fat milk, which of course would separate are forced together to mix at high pressure.

Researchers are new methods, such as "molecular beam epitaxy" mix to combine this disparate elements.The results, Goldman says, are more dramatic than smooth milk.

"" Not matching High alloys have very unusual properties,"Goldman said.""You can add an item to only a pinch and drastically change the electrical and optical properties of the alloy."

Goldman is Professor in the departments of physics, materials science and engineering.Other U-M physicists and engineers and researchers from Tyndall National Institute in Ireland include your team.

Solar cells convert energy from the sun into electricity by absorbing light. However, different materials absorb light at different Wellenl?ngen.Die most efficient solar cells consist of several materials that can capture a larger part of electromagnetic radiation in sunlight.The best solar cells are today still missing a material that can make use of the infrared light from the Sun.

Goldman's team of samples of gallium arsenide nitride, insufficiently used a high not matching alloy which is peppered with nitrogen, which can tap into the infrared radiation.

The researchers to the molecular beam epitaxy coax-includes the nitrogen with your other elements to mischen.Molekularstrahlepitaxie evaporate pure examples of non-matching items and combined in a vacuum.

Next, measured convert researchers of the alloy's ability to heat into electricity.You wanted to determine, whether its 10 parts per million of nitrogen were as individual atoms or as cluster verteilt.Sie found out that in some cases grouped the nitrogen atoms what the prevailing had in contrast to the "Anti crossing Band" model predicted.

"" We have shown experimentally, the band anti-crossing model is too simple to explain the electronic properties of high mismatched alloys,"said Goldman.""It is not quantitative more their exceptional optical and electronic properties erl?utert.Atomic clusters have significant effects on the electronic properties of the alloy films."

If researchers can learn to control, said the formation of this pile materials could build more efficient at converting light and heat into electricity, Goldman.

"The availability of more efficient Thermoelectrics about practical to generate power from waste heat, for example, produced engines power stations and car" Goldman said.

This research is in physical review b online published. the paper is entitled "nitrogen composition depending on electron effective mass in gallium arsenide nitride."

This research is funded by the National Science Foundation for solar and thermal funded Science Foundation Ireland and the Centre energy conversion, an energy Frontier Research Center by the U.S. Department of energy.

Story source:

The above story is made of materials from the University of Michigan reprinted provided (with editorial adjustments of ScienceDaily staff).

Journal reference:

T. Dannecker, y. Jin, H. CHENG, C. Gorman, j. Buckeridge, C. Uher, S. Fahy, C. Kurdak, R. Goldman.Nitrogen composition dependence of the electron effective mass in GaAs_ {1?x} N_ {X}.Physische review B, 2010; 82 (12): 125203 DOI: 10.1103/PhysRevB.82.125203

Note: If no author is specified, instead cites the source.

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