**7. Some other solar cells**

Mainz et al. demonstrated that rapid thermal sulphurisation of sputtered Cu/In precursor layers is suitable for industrial production of thin film photovoltaic modules. Yoosuf et al. (2005) investigated the effect of sulfurization temperature and time on the growth, structural, electrical and photoelectrical properties of b-In2S3 films. Nishiokaa et al. (2006) evaluated the temperature dependences of the electrical characteristics of InGaP/InGaAs/Ge triple junction solar cells under concentration and found that for these solar cells, conversion efficiency decreased with increasing temperature, and increased with increasing concentration ratio owing to an increase in open-circuit voltage (Nishiokaa et al., 2006). Phani et al. (2001) described the titania solar cells that converts sunlight directly into electricity through a process similar to photosynthesis and has performance advantages over other solar cells, which include the ability to perform well in low light and shade, and to perform consistently well over a wide range of temperatures and low cost.

Some commercial manufacturers use self-organised nanostructured glass surfaces to improve system efficiencies b yaround 10%. More carefully constructed silicon nanostructure that mimic the eyes of species of moth promise further improvements but are currently too expensive to implement (Bagnall and Boreland, 2008). However, nanoembossing and nano-imprinting technologies are rapidly developing and it is now possible to envisage regular commercial use of nanostructured broad-band antireflective surfaces within the near future, enhancing system efficiencies by more than10%(Fig.15).

The most promising application fields for the energy conversion domain will be mainly focused on solar energy (mostly PV). Hence to improve the conversion efficiency, structures from nanotechnology products that absorb more sunlight are emphasized: devices such as nanotubes, quantum dots (QDs), and "hot carrier" solar cells.
