Compared with dye molecules, semiconductor iron oxide, the molecular arrangement is regular, and the electron orbit is not limited to the position of the molecule, but exists throughout the crystal. Only the part of kinetic energy forms an energy band. Here, the energy band occupied by electrons is called a valence band, and the unoccupied energy band is called a conduction band, which corresponds to HOMO and LUMO of molecular orbitals, respectively. The part between the band and the band

It is called a belt. Titanium dioxide has a band gap of 4 eV and absorbs ultraviolet rays, but visible light is transmitted through it, so it cannot be used for solar cells. However, if combined with a dye, the dye molecules can absorb visible light and generate electrons and holes, and the electrons enter the conduction band of the semiconductor titanium dioxide, thereby achieving the purpose of power generation.