Electrochemical deposition of organic semiconductor thin film and screening by scanning electrochemical microscopy

Abstract

A perylene tetracarboxylate (PTCA)-based organic semiconductor polymer was deposited onto an indium tin oxide (ITO) glass by means of one-step electrochemical oxidation at a constant potential. The obtained PTCA thin films were characterized via several physicochemical and spectroscopic methods. The thickness of the deposited film can be controlled by tuning the deposition time. The energy of the lowest unoccupied molecular orbital and the optical band gap of the film (−2.1 eV, 3.6 eV) were higher and smaller, respectively, than those of the bare ITO (−4.8 eV, 3.7 eV). Loading a PTCA thin film onto an ITO glass created a type of photoanode material that exhibited enhanced photocurrent responses and improved photoelectrochemical water oxidation ability compared with that of the bare ITO film. The photoelectrochemical ability of the PTCA film array (with different thicknesses) for water oxidation can be rapidly screened in a neutral solution through the substrate generation-tip collection mode of scanning photoelectrochemical microscopy (SPECM). Among the array, the line of PTCA-600s/ITO produced the largest photocurrent (9.2 nA) in a 0.1 M KCl solution under visible light irradiation. Bulk ITO electrodes decorated with the film under the same preparation conditions confirmed the results of the SPECM screening. In addition, SPECM can be used to further verify the photogenerated carrier transfer mechanism by redox competition mode. This work offers insight into the preparation and screening of photoelectrochemical organic semiconductor material.