Reply #5: Thanks for that link. Same basic idea, very different materials. [View All]

[eppur_se_muova]

more from article in the OP:

RSL Energy will commercialize Berkeley Lab’s multi-band technology which incorporates a unique new semiconductor material that can achieve the efficiencies of a triple junction device with the manufacturing cost and simplicity of a single junction device.

Developed by a research team led by Kin Man Yu and Wladek Walukiewicz, the Berkeley technology uses a new ZnMnTe semiconductor material with multiple energy gaps. This type of multiband semiconductor had been theoretically predicted but never before made, and the work won the R&D 100 Award in September of this year and the R&D 100 Award for Most Promising Technology in October of this year.

The power conversion efficiency limit for a solar cell employing a single semiconducting material is 31%. The primary basis of this limit is that no single material can absorb light across the full range of solar radiation, which has usable energy in the photon range of 0.4 – 4 eV (infrared to ultraviolet). Light with energy below the bandgap of the semiconductor will not be absorbed and thus not be captured for energy conversion. Light with energy above the bandgap will be absorbed, but the excess energy above the bandgap will be lost in the form of heat. Decades of research in developing single-material solar cells has led to cell efficiencies close to the theoretical limit; the best cell of this type has an efficiency of 25.1%.

I've highlighted in bold what may be the most important phrase in the article -- lower mfg cost. The UniSolar materials use Si/SiGe layers, and the multiple layers add to the mfg cost.

Interestingly enough, the article mentions they have another candidate:

In addition, RSL Energy is also commercializing the InGaN multi-junction technology of Cornell and Berkeley Lab, which is expected to provide outstanding thermal and radiation properties necessary for next-generation concentrator-based photovoltaics (CPVs) utilized in distributed energy power generation. RSL Energy believes that the InGaN cells could achieve efficiencies of more than 48%.