Figure 2.

Operation of n-type semiconductor (left) and p-type semiconductor (right) in a PEC cell. Electron donors (D) in the redox couple are oxidized by the photoactive species, thereby resulting in the loss of an electron which is then relayed to the collector (underlying conductive substrate), thus yielding an anodic current. Alternatively, electron acceptors (A) in the redox couple gain an electron from the photoactive species following their reduction upon light illumination, subsequently giving rise to a cathodic current. E_g, E_f, WE, RE, CE represent band gap energy, fermi energy, working electrode, reference electrode and counter electrode respectively.