Essentially what this paragraph says is that, when the absorption 
spectrum of the dye-sensitized TiO<sub>2</sub> is compared with the spectrum
of solar radiation at Earth's surface for lattitudes around those of
Europe and the United States, 46% of the solar spectrum is covered by
the absorption spectrum.  That is, the dye-senstitized TiO<sub>2</sub> will
harvest about 46% of the incident light at lattitudes close to those of
Europe and the United States.  This is a reason that these solar 
cells are not as efficient as they could be - even though they absorb
nearly 100% of ultraviolet light, there is little to no ultraviolet light in
the solar radiation that hits the solar cells.