Magnesium nickel hydride (Mg2NiH4) is long known to be a semiconductor, but nobody has ever really tried to take advantage of that in technological applications. The band gap of this semiconductor is known to be a bit above 1.5 eV, which is quite close to the ideal band gap for a semiconductor in a solar cell.
One of the issues of why magnesium nickel hydride has never really been investigated for this purpose, is that most research on this material has been done on powders. It's quite intuitive that you cannot make a solar cell of a powder (although an innovative company actually is trying). So, it is crucial to be able to make the compound in a suitable form for solar cells; namely in the form of a film. That has been done earlier, but it is usually done by hydrogenation of a metallic magnesium nickel layer through a palladium cap. That type of film is, however, not so easy to work with, as the hydrogen will release from the film if you keep it in air, and you will be left with two layers of metals. Using reactive sputtering, on the other hand, we show that we can make films efficiently and that the films are quite easy to handle afterwards. This is really promising with regards to the actual use of this semiconductor in technology.
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A Mg-Ni-H film with Al electrodes for electrical measurements.
* Paper: Magnesium nickel (hydride) thin films deposited by magnetron co-sputtering
Published in Journal of Alloys and Compounds
DOI: 10.1016/j.jallcom.2012.02.155
By the way, see also this nice article about our project that was recently published on the popular science news-site ScienceNordic: http://sciencenordic.com/new-material-solar-cells
