**Acknowledgements**

**4.1. How does the DSSC work?**

360 Titanium Dioxide - Material for a Sustainable Environment

**4.2. Uses of titanium dioxide in DSSC**

**5. Summary and perspectives**

Nowadays, many groups and results mentioned that TiO<sup>2</sup>

to other metal oxide semiconductors such as ZnO, SnO<sup>2</sup>

TiO2

When the solar light is irradiated, the dye sensitized it, and the electron excited from the valence band (VB) to the conduction band (CB) of the dye leaving a hole in the valence band. After that,

and the cathode is covered with a platinum layer. From Ref. [55]. Reprinted with permission from Springer Nature 2003.

ticles which facilitate the swimming of the electrons to the FTO anode substrate and then to the Pt cathode to generate electricity. On the other hand, the redox reaction occurs in the iodine electrolyte to facilitate the formation of the electron to fill the hole founded in the valence band

 is used for DSSCs for the following key properties: (i) is a suitable band that adjusts for electron injection from most commercial dyes, (ii) has a high surface area which is suitable for higher dye loading, and (iii) has high electronic mobility for photo-generated electron collection.

structure which is important to achieve high charge collection efficiency and more electron transportation. These features enable a good electrode while fabricating a typical DSSC device.

Since many years, titanium dioxide nanomaterials have been highly discussed because of their application in solar to electricity conversion for their matching with modern technologies. The persistent permeation in the synthesis and modifications of titanium dioxide

nanopar-

) and the redox

is filled with a dye,

is the best available choice compared

, and so on due to the internal network

the electron moves from the valence band of the dye to the valence band of the TiO<sup>2</sup>

**Figure 8.** Schematic diagram of a solar cell sensitized by dye. The nanoporous semiconductor (TiO<sup>2</sup>

electrolyte are founded between two substrates, covered with fluorinated tin oxide (FTO). The TiO<sup>2</sup>

of the dye to regenerate the electron in the cell, and the process occurs continuously.

The authors would like to extend their sincere appreciation to the Central Metallurgical Research and Development Institute, Egypt, for its financial support to pursue the work.
