(1), where I photo_max is the maximum current density,  is the absorption coefficient (taken as a mean value over the solar spectrum), d is the film thickness, L D is the diffusion length and d s is a dead thickness at the contacts with a high recombination velocity. Fitting the I photo (d) curve (Fig. ) with equ.(1), yields a diffusion length of L D = 320 nm, a dead layer thickness of 60 nm and an absorption coefficient of 6 . 10 4 cm -1 . This value of L D is significantly smaller (about a factor of 6) compared to the diffusion length derived from time-resolved microwave conductivity measurements (TRMC), reported recently. This can be explained by the anisotropy of WSe 2 : while in a PEC experiment, the transport along the c-axis of the (0001)-oriented WSe 2 crystallites (i.e.