Wednesday, February 4, 2009

Prismatic Solar Cells

Different photovoltaic materials have varying efficiencies when converting certain colors/wavelengths of light into electricity. If you split the sunlight apart with a prism, you could direct the optimal color of light to a series of different photovoltaic surfaces. Simultaneously, these surfaces could be arranged in a stairstep fashion to collect the light perpendicularly, fitting more photovoltaic surface area into troughs than would be available on a flat surface.



  1. Interesting! My biggest concern with this is that the solar energy harvested as electrical energy depends in large part on the angle of incidence, so I'm thinking that that you'd still want the PV strips to be horizontal. That said, the optimization based on wavelength sounds great!

  2. right - but if the light hits a prism, it's going to bend it, so it will come out the other side scattered and spread at some angle - which you can then capture with a surface that is normal to it (but slanted relative to the original sun rays). i guess the scale in the picture i made is exaggerated.

  3. Ok, got it now! Huh... do you have any idea how much more efficient a system like this could be if you selected different materials for different wavelengths? This actually is really intriguing. Hmm. =)

  4. i haven't done any analysis or anything, but i imagine you could gain some percentage points. the efficiency of any given PV material has an optimal wavelength, which rolls off as you move away from it. to the extent that you can cheaply capture the optimal light...seems like you could improve efficiency to some degree.

    maybe it would just be 2-tiered; like you have one PV material that likes red light and another that likes violet light.

  5. this is essentially done already in multiple junction solar cells, where the different layers are actually stacked, and they are thin enough to be "transparent" to certain wavelengths of light that pass through to the layers underneath:

    “The most widely explored path to higher efficiency solar cells has been to use multiple p-n junctions, each one tuned to a particular frequency of the spectrum. ...The majority of tandem cells that have been produced to date use three such layers, tuned to blue (on top), yellow (middle) and red (bottom).”

    See also: