New Methodology of Organic Electrochemical Synthesis - Fundamentals and Applications of Organic Electrochemistry - page 302

The design of the junction of the layers is
important to induce charge separation
efficiently before deactivation of the exciton.
The construction of a path to the electrode
surface of the generated charge carriers is also
important for high photo-electron conversion
efficiency.
7.1.3 Dye-sensitized Solar Cells [5,6]
Semi-conductor electrode like metal oxide can
generate electric energy based on the principle
of photocatalysts. A photo-excited electron in a
semi-conductor electrode reaches the electric
circuit and the remaining hole receives
electrons from a redox system in the electrolyte,
followed by electron transfer from the counter
electrode to the redox system. Because of the
relatively wide band gap of semi-conductor
electrodes, UV light is usually employed to
drive this type of photovoltaic cell.
Dye-sensitized solar cells (DSSCs) work in the
visible region of solar light using organic dye on
a semi-conductor electrode as the
photo-sensitizer. The organic dye should have a
higher LUMO level than the semi-conductor
electrode and a lower HOMO level than the
redox system in the electrolyte. A typical DSSC
system, known as the Grätzel cell, is composed
of a transparent anode, titanium oxide (TiO 2 )
coated with ruthenium complex, an I − /I 3 −
redox system in electrolyte and a Pt cathode
( Figure 7.4 ). The voltage generated in the DSSC