Photoelectrochemical processes in organic semiconductor: Ambipolar perylene diimide thin film

Abstract A thin film of N,N′ -dioctadecyl-3,4,9,10-perylene tetracarboxylic diimide (PTCDI-C 18 ) is spin-coated on indium tin oxide (ITO) glass. Using the PTCDI-C 18 /ITO electrode, we fabricate a photoelectrochemical cell with the ITO/PTCDI-C 18 /Redox Electrolyte/Pt configuration. The electrochemical properties of this device are investigated as a function of hydroquinone (HQ) concentration, bias voltage, and wavelength of light. Anodic photocurrent is observed at V ≥ −0.2 V vs. Ag/AgCl, indicating that the PTCDI-C 18 film acts as an n-type semiconductor as usual. However, when benzoquinone (BQ) is inserted into the electrolyte system instead of HQ, cathodic photocurrent is observed at V ≤ 0.0 V, displaying that PTCDI-C 18 abnormally serves as a p-type semiconductor. Hence the overall results reveal that the PTCDI-C 18 film can be an ambipolar functional semiconductor depending on the redox couple in the appropriate voltage.