Nanomaterials: Properties, Preparation and Applications - Environmental and Human Health Impacts of Nanotechnology - page 68

Semiconductor/dye

Junction

Semiconductor

e - h +

h +

Electrodes

e -

W

W

Electron

Electrical device

Figure 2.21 A simplifi cation of a solar cell with electrical device W connected so work may
be done.

(Figure 2.21). The impact of nanotechnology on the development of the solar cell
dates back almost as far as the solar cell itself (1954) (Saunders et al. , 2007 )
However, it has not been until more recently that the use of nanoparticles in this
type of application has received so much attention. There are several issues that,
where they to be resolved, would make solar power a viable method for energy
production in most countries. Firstly, it is important that all of the light falling onto
the cell is captured. However, there are very few materials which will readily
capture light at such a broad spectrum of wavelengths and also produce the effects
needed to convert the incident light into energy. The second issue is the effi ciency
of the conversion of light into electricity itself and the third is the method of
manufacture. Ideally, solar cells would be manufactured by wet chemical processing
routes on a range of materials such as plastics. There are three main approaches to
these problems which use nanoparticles. The fi rst is to prepare solar cells with dif-
ferent materials in a nanoparticulate form. The correct layering of these materials,
of suffi ciently high quality, is likely to result in improvements in performance. The
second approach is to use a nanoparticle as an electrode, as in the DSSC discussed
earlier, and the third is to use a nanoparticle as a composite with a semiconducting
polymer. This latter application is still in its infancy. There is a wide range of materi-
als currently used and under investigation (Table 2.5). Some of these materials have
yet to see commercial use; however Table 2.5 shows the broad range of materials
currently under consideration.

2.6.2.4 Waste Remediation

The use of iron nanoparticles for the decontamination of land is well known. It has
been shown that nanoparticles of iron and those of palladium and iron are excellent