**7. Conclusions**

In this chapter, we experimentally demonstrated that a new photosensitive material can be used to realize holographic solar concentrators.

Two configurations of holographic lenses were investigated: spherical in-line lenses and cylindrical off-axis lenses. The chromatic aberration of the spherical lens was characterized, proving a decrease of the focal length as the incident wavelength increases. Furthermore, the beam profile was characterized for both the proposed holographic lens in their focus. Performances of holographic lenses were compared to those of conventional optics. Some lower performances of holographic lens highlighted with respect to conventional optics, such as higher axial chromatic aberration and lower ability to concentrate light in the focus, are rewarded with a lower size, lower weight and lower cost. However, chromatic aberration can be useful to reduce cooling requirements. Indeed, considering that the PV cell will be placed at the focal length in the visible region, the infrared region will be focalized very far, avoiding the thermal overheating of the photovoltaic cell due to the absorption of infrared radiation.

Finally, a preliminary study of the influence of the thermal stress and the behaviour of the photopolymer in the absence of pressure (space conditions) revealed that the proposed photosensitive material could be suitable in space environment. Therefore, we are quite optimistic that our experimental results can open the way to the fabrication of efficient, cheap and lightweight holographic solar compatible with space applications.
