Photovoltaic energy conversion is one of the best alternatives to fossil fuel combustion. Petroleum
resources are now close to depletion and their combustion is known to be responsible for the
release of a considerable amount of greenhouse gases and carcinogenic airborne particles.
Novel third-generation solar cells include a vast range of device designs and materials aiming
to overcome the factors limiting the current technologies. Among them, quantum dot-based
devices showed promising potential both as sensitizers and as colloidal nanoparticle films.
A good example is the p-type PbS colloidal quantum dots (CQDs) forming a heterojunction
with a n-type wide-band-gap semiconductor such as TiO2 or ZnO. The confinement in these
nanostructures is also expected to result in marginal mechanisms, such as the collection of hot
carriers and generation of multiple excitons, which would increase the theoretical conversion
efficiency limit. Ultimately, this technology could also lead to the assembly of a tandem-type cell
with CQD films absorbing in different regions of the solar spectrum