Double helix of inorganic SnIP semiconductor eyes solar cells

Double helix of inorganic SnIP semiconductor eyes solar cells

Technology News |
By Nick Flaherty

Comprising tin, iodine and phosphorus, the novel semiconductor exhibits extraordinary optical and electronic properties, as well as extreme mechanical flexibility, with centimetre-long fibres that can be arbitrarily bent without breaking. The thinnest SnIP fibres to date comprise only five double helix strands and are only a few nanometres thick.

Through appropriate doping, the researchers expect the novel material to lend itself to many applications in the electronic industry, from energy conversion in solar cells and thermoelectric elements to photocatalysts, sensors and optoelectronic elements. What’s more, the material is stable up to around 500°C and the SnIP double helices can be suspended in solvents like toluene to produce thin layers through ink jet printing or spray deposition.

“This property of SnIP is clearly attributable to the double helix,” says Daniela Pfister, who discovered the material and works as a researcher in the work group of Tom Nilges, Professor for Synthesis and Characterization of Innovative Materials at TU Munich. “SnIP can be easily produced on a gram scale and is, unlike gallium arsenide, which has similar electronic characteristics, far less toxic.”

The double helical SnIP molecule.

According to the researchers, SnIP is the one-dimensional equivalent of carbon nanotubes, and they are only at the beginning of figuring out how to make the best of its properties.

“We are only at the very beginning of the materials development stage,” says Daniela Pfister. “Every single process step still needs to be worked out.”

An interesting property of the material is its chirality, (the double helix strands of SnIP come in left and right-handed variants), possibly hinting at special optical characteristics for if it was possible to synthesize only one variant.

Through theoretical calculations, the researchers expect a whole range of further elements to form these kinds of inorganic double helices, they have secured patent protection and are looking for ways to synthesize other materials with similar properties as those of SnIP.

An extensive interdisciplinary alliance is working on the characterization of the new material: Photoluminescence and conductivity measurements have been carried out at the Walter Schottky Institute of the TU Munich. Theoretical chemists from the University of Augsburg collaborated on the theoretical calculations. Researchers from the University of Kiel and the Max Planck Institute of Solid State Research in Stuttgart performed transmission electron microscope investigations. Mössbauer spectra and magnetic properties were measured at the University of Augsburg, while researchers of TU Cottbus contributed thermodynamics measurements.

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