The fundamental absorption and transmittance of
CdS nanotubes are especially helpful in understanding
their unique light manipulation characteristics. UVvisible
spectroscopy measurements were conducted
over a wavelength range of 300 to 900 nm, which covers
most sunlight photons with an energy higher than
the band gap of the CdTe absorber. Figure 4(a) shows
the transmittance spectrum of the CdS nanotubes
embedded in the AAO template. This transmittance
spectrum was acquired before the partial removal of
the AAO membrane. Of course, the AAO membrane
would subsequently be partially removed before the
CdTe layer was deposited.