I don't know about this particular solar cell, but: 1. different wavelengths can propagate further below the surface of the receiving chip; this effect has been used for some color camera chips. 2. if one can spread the Ge and In extremely thinly -- which is probably required by #1 -- then the amount of such material required is quite small. Ultimately, solar cells will probably do what plants have done for >1 billion years: they "downconvert" certain wavelengths for handling by molecules that can only process longer wavelengths. At 10:34 AM 5/18/2016, Warren D Smith wrote:
35.4% energy conversion (sun->electric) efficiency achieved. The light was split into 4 spectral bands each handled with a different semiconductor: Ge: 0.67eV Si: 1.1eV GaInAs: 1.41eV GaInP: 1.88eV I don't understand their splitting scheme. Can it be used with scattered sunlight, i.e. which is not coming from just one direction? In any event, it seems to me this whole approach probably is totally uneconomical because Ge and In are rare. http://newsroom.unsw.edu.au/news/science-tech/milestone-solar-cell-efficienc...
(Even greater efficiency has been achieved by the same team but using concentrated sunlight.)
-- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)