Textile and semiconductor processes were combined to produce a flexible solar panel
by depositing silicon thin film onto woven polyester. Semiconductor processes such as
evaporation, Plasma Enhanced Chemical Vapour Deposition (PECVD) and RFsputtering
were done under vacuum conditions. Microwave PECVD proved difficult for
textile substrates as the weave was damaged using parameter settings commonly
used for conventional substrates such as silicon wafers and glass. PECVD parameters
such as temperature, gas flow-rate, mixture, pressure and power were adjusted to
allow the textile to be processed and a good quality silicon thin film to be deposited. An
extra conductive layer was introduced between the textile and metal back-contact to
support the cell. The silicon film structure changed from amorphous to mixed crystal
growth in an amorphous matrix, as revealed by Raman spectroscopy and light
transmission. The silicon Raman spectrum often had three peaks with the middle one,
a fingerprint for nanocrystal growth with a hexagonal wurtzite structure in between the
amorphous and crystalline peaks. Process conditions for pure amorphous and
microcrystalline structures were also established, requiring two peaks to fit the Raman
spectrum. Different structures have different band-gap energies and these were
determined by measuring the variation in light transmission. An amorphous structure
has a band-gap energy of 1.8eV while a crystalline silicon structure has a band-gap of
1eV and a mixed nanocrystalline content has an intermediate value which depends on
the crystal size. A microcrystalline structure has a band-gap of 1.6eV
