3.5. Photoinjection in TiO2-Dye Complex
As the light shines on the surface of dye, the electron from the HOMO of dye are excite to its LUMO after which the electron is moved to the conduction band of semiconductor TiO2 [80]. This transfer of electron could be of two types: direct photoinjection and indirect photoinjection. The indirect transfer involves transition HOMO-dye to LUMO-dye toCB-TiO2 whereas the direct transfer comprises of transition HOMO-dye to CB-TiO2. These two processes are sketched in figure 7.