However, insertion of a metallic interlayer, to screen the p-Si and a-TiO2 materials from each other, resulted in complete removal of the non-faradaic process, as determined by EIS. This implies a charging mechanism exists at the interface between the p-Si and a-TiO2, which could involve the presence of the defect band states, despite the fact that these states do not influence the overall performance of these photocathode devices.