Photoelectrochemical scanning droplet cell microscopy (PE-SDCM).

Principles of localised photoelectrochemistry are summarised and an experimental approach is described that allows the performance of the most important photoelectrochemical experiments within a diameter of 100 μm. Various light sources, such as a continuum emitter with a monochromator, LEDs, and lasers are coupled into a multi-mode fibre to illuminate a small spot that is wetted by the electrolyte from a capillary. Reference electrode, counter electrode, and optical fibre are installed in the capillary system. The performance of this system is demonstrated by photocurrent measurements on n-doped Si and p-doped Si as model substrates. A thickness-graded aluminium thin film for partial shadowing on Si proves the applicability for material library investigations in combinatorial materials science. Further experiments demonstrate the possibility of electrical light chopping as well as impedance spectroscopy with subsequent Mott-Schottky analysis for the determination of charge-carrier concentration and type, flat-band potential, and inversion layer formation. Photoelectrochemical scanning droplet cell microscopy (PE-SDCM) is an extremely versatile tool for the screening of water splitting photoelectrodes, the characterisation of photocatalysts, and high throughput characterisation of microgram amounts of new solar cell materials.