Basically three types of conduction mechanism take place for extrinsically conductive composites above the room temperature; electric field radiation, hopping/tunneling of electrons, and electron conduction
through particle-particle contact [32, 33].
ITO, FTO)-) a membrane enabling transport of protons via a pulsated thin water gap-) an external wire for electron conduction
between electrodes-) a cathode carrying an hydrogenase-enzyme mimic over a porous electron-conducting support in order to recombine protons and electrons into pure molecular hydrogen at the opposite side of the membrane.
However, the small absorption overlap with the solar spectrum limits the photocurrent generation in fullerene acceptors, and their deep energy level for electron conduction
limits the open-circuit voltage.
Among them, the most common mechanism is based on the electron conduction
between the conductive filler particles by electron tunneling and hopping, when the interparticle distance is in the neighborhood of 100 [angstrom].