Corrosion photocurrent efficiency

In a subsequent work [182], it was shown that the photoelectrochemical performance of InSe can be considerably improved by means of selective (photo)electrochemical etching. Interestingly, whereas the cleavage vdW plane showed little improvement, the photocurrent in the face parallel to the c-axis was doubled. Note that, in contrast to InSe crystals cleaved in the plane perpendicular to the c-axis that are almost defect free, the crystals cut in the plane parallel to the c-axis contain a high density of defects on their surface which leads to a high rate of electron-hole recombinations and inferior quantum efficiency. The asymmetry in the role of electrons and holes, as manifested, e.g., in the fact that surface holes carry out the selective corrosion of the semiconductor surface in both cleavage orientations, was discussed. 

The efficiency of photoelectrochemical devices is based on effective charge transfer while suppressing surface recombination and corrosion. While the photocurrent is a direct measure of the irreversibly transferred electrons, it is not trivial to obtain a measure for the losses at surfaces due to recombination. As will be shown in Section 2.3.1, stationary microwave reflectivity is a method that measures the integral of the excess minority carrier profile. Such profiles are shown in Figures 2.3-2.6. The simultaneous recording of photocurrent and excess microwave reflectivity in an electrochemical cell allows the assessment of the relative contributions of kr and Sr for well-defined systems. These parameters are defined as follows ... 

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