New material can absorb more infrared

Researchers in Spain are working on a new solar cell material that has a higher theoretical absorption rate than conventional semiconductor solar cells. The researchers throw titanium and vanadium into the conventional solar cell material mix so it can use the infrared spectrum and potentially boost efficiency of solar cells.

The new material provides a “stepping-stone” for electrons to move from a low energy level to an intermediate energy level as they absorb photons, allowing more photons of lower energy levels (and thus different parts of the light spectrum) to be utilized.

So while some efficiency research goes into breaking down what is absorbed into specific wavelengths or trapping light for greater absorption, this technology basically helps to cast a really wide net to increase how much light can be captured and turned into energy.

The new material hasn’t been tested yet for just how much it can gather, but it has a theoretical absorption rate of 63% so the scientists reason that the actual absorption will be higher than conventional semiconductor solar cells.

This is a step up from the first “stepping-stone” solar cells that achieved a theoretical capture rate of 57%.

In geek-speak:

Calculations for indium thiospinel semiconductors substituted at octahedral sites with isolated transition metals (M=Ti,V) show an isolated partially filled narrow band containing three t2g-type states per M atom inside the usual semiconductor band gap. Thanks to this electronic structure feature, these materials will allow the absorption of photons with energy below the band gap, in addition to the normal light absorption of a semiconductor... leading to an enhancement of the absorption coefficient in both infrared and visible ranges of the solar spectrum. This electronic structure feature could be applied for developing a new third-generation photovoltaic cell.

So, the early versions of the materials match the properties predicted by the researchers to enable it to absorb infrared. Now we just have to wait for the material to be turned into an actual solar cell so we can know just what the size of this improvement is.

Via TreeHugger, New Scientist, Physical Review Letters; photo via vogelium