Although it has been close to 60 rears since the first operational silicon
solar cell was demonstrated, the last 15 years have seen large improvements
in the technology, with the best confirmed cell efficiency improved by ove
r 50%. The main drivers hare been improved electrical and optical design of
the cells. Improvements in the former area include improved passivation of
contact and surface regions of the cells and a reduction in the volume of
heavily doped material within the cell. Optically, reduced reflection and i
mproved trapping of light within the cell have had a large impact. Such fea
tures have increased silicon cell efficiency to a recently confirmed value
of 24.7%. Over recent years, good progress has been made in transferring so
me of the corresponding design improvements into commercial product with co
mmercial cells of 17-18% efficiency now commercially available, record valu
es of a mere 15 years ago, The theory supporting these improvements in bulk
cell efficiency shows that thin lavers of silicon, only a micron or so in
thickness, should be capable of comparably high efficiency.