ABSTRACT
The impressive success of very high conversion efficiencies obtained
with crystalline silicon (c-Si) has triggered the search for novel
concepts which overcome the fundamental efficiency limits of
c-Si solar cells. The market has seen a dramatic reduction of
module costs due to up-scaled production. However, ongoing long-
term cost reduction requires not only up-scaled production and
increasingly sophisticated technologies but also the implementation
of fundamentally new concepts which overcome the physical
limitations of current technologies. One approach to overcoming the
Shockley-Queisser limit [1] of c-Si is to introduce a second band gap
which still essentially consists of c-Si [2, 3], which together with the
first cell forms a tandem cell. This second band gap is provided by a
dense array of silicon nanocrystals (Si NCs) embedded in a Si-based
dielectric. The band gap of such a composite material can be tuned
from that of bulk c-Si up to approximately 2 eV and is well suited for
the top cell in the all c-Si tandem cell.
