Renewable Energy

Is black silicon the way to make cheaper solar power?

I came across an article today talking about how black silicon will revolutionize solar power. The idea developed at Harvard (and now at a company called SiOnyx) is basically to blast the surface of a silicon wafer with a high intensity laser for a very short interval. This short time “melts” the silicon and when it comes back together it has a structure allows the structure of the silicon to absorb more light. They also utilize a new type of doping, (doping is insertion of low quantities of specific elements, such as phosphorus, into silicon in order to change the properties of the silicon. Depending on the type of dopant the silicon may want to release an electron or absorb one); the laser process likely allows better penetration of the dopants into the silicon, which usually are accelerated into the silicon with HUGE magnets. There aren’t specifics about the entire process, but as you can see in the picture below, the silicon seems to stretch upwards creating cones of silicon. I would guess that the process is similar to carbon nano-tubes where they also use a laser to blast the carbon. It also makes sense that the process would work for silicon given the similar structure between carbon and silicon.

Courtesy of SiOnyx

Again, I don’t know the specifics of how the final product works better, but my guess would be that the cones are much better and capturing light, due to the higher surface area. When the light hits these more sensitive nodules, the energy “knocks” an electron loose (just as in regular PV cells), which then contributes to the overall current coming from the cell. Also of note is how the dopants shift the sensitivity of the silicon to a lower wavelength. In this case, it is shifting it down into the red and infrared regions of the spectrum, which allows for more energy to be absorbed by silicon, as opposed to reflected. This also is the namesake characteristic of this technology, because in theory “black” silicon would absorb all light (as opposed to a theoretically worthless “white” silicon that would reflect all light). The higher amount of cells hit by light (due to more surface area) and the greater sensitivity to low wavelength light such as infrared (which our bodies interpret as “heat”) gives this new silicon a much higher overall absorption and translation into usable electrical energy.

I like this idea because it lets existing solar facilities be transformed easily into solar cell facilities. This new capacity could then be absorbed by local micro-factories, putting the solar arrays together and hopefully driving the cost to the consumer down. As more and more fabrication facilities are shut down due to a possible recession, they could quickly be modified to start outputting less complicated solar cells in higher volumes. The SiOnyx equipment would provide the final processing necessary to have the higher efficiency panels.

I only know what I have read online, but I like what I have seen thus far (plus I tend to trust researchers from Harvard more than just some schlub off the street). It seems feasible in the short term and has much broader appeal and use than ideas like “dancing to save the world“. Check out the above article and if you have any thoughts, please leave them in the comments.