At the risk of beating a dead horse, I take issue with the Update on the post. The researchers have not made a solar panel or a solar cell. They have made a sheet of "photoactive" material and have measured how it absorbs light. The MIT Tech Review article says "Computational models suggest that the material could be used to make solar cells that would convert 15 to 20 percent of the energy in sunlight into electricity". Such models are highly dubious when actual solar cells have not been demonstrated, and major identifiable hurdles need to be crossed before that happens. Although I agree with other posters that it is significant that very little Si is required in this material, it is hard to say much about manufacturing cost either before a working device or device architecture exists.

This is interesting work, but it is in a very immature stage of development. They seem to be no where near demonstrating a practical solar cell, and speculated conversion efficiency numbers like 86% are laughable. One of the fundamental limitations of a cell based on Si wires is that the higher a photon's energy is over the bandgap of Si, the more energy is lost as heat. I believe the theoretical maximum conversion efficiency for a Si solar cell is around 30%, and commercially viable cells are limited to around 20% because of practical issues in creating solid state cells such as making electrical contacts to the device, the high cost of making higher efficency (20+%) Si cells. This work doesn't begin to address such issues. I think it is unfortunate that over-hype like this can take luster off of progress in photovoltaics that seems less spectacular but is much closer to practical realization.

It's worth noting that the Walkman's lightweight headphones were made possible by the discovery and development of samarium cobalt (SmCo) permanent magnets in the early 1970's. Materials (e.g. AlNiCo) that existed before that were not only much weaker, but could only be made in elongated shapes, resulting in much bulkier voice coil assemblies.