Screening of Photoactive Dyes on TiO2 Surfaces Using Scanning Electrochemical Microscopy

Screening the photoelectrochemical activity of dyes on TiO2 surfaces is becoming increasingly relevant as industry tries to expand commercialization of dye sensitized solar cells (DSSCs). Here we demonstrate how a simplified version of scanning electrochemical microscopy (SECM) together with photoexcitation of dispensed arrays of dye spots can be used as a powerful yet low-cost screening method. A standard SECM configuration uses separate reference and auxiliary electrodes together with an ultramicroelectrode (UME) working electrode (WE) and the substrate as an optional second WE. In this work we evaluate different electrode configurations, measurement modes, and measurement parameters to optimize photocurrent image quality. We propose an innovative two electrode configuration that is a close representation of a real DSSC in operation. This simplifies the required instrumentation (no bipotentiostat or reference/auxiliary electrodes) compared to the more conventional four electrode approach, reducing costs and allowing the screening method to be readily used by industry. Using this approach, the simultaneous screening of different dyes is demonstrated, and the relative. photocurrent of dye samples in the arrays is shown to be comparable to the relative performance of full devices.