GoKawiila–c, HAADF image and corresponding EDS map of the PTI single crystal, depicting the spatial distribution of Rh and Co signals (a), their line profiles (b) extracted along the dotted line in a and quantitative EDS analysis that measures the probability of photogenerated electrons and holes migrating towards the P or B facets (c). d–f, HAADF image and its EDS map of the PTI-E ‖ single crystal, showing the distribution of Rh and Co signals (d), their line profiles (e) along the dotted line in d and photocarrier migration probability towards the P facet or crystal corners (f). g–i, HAADF image and its EDS map of the PTI-E ⊥ single crystal, showing the location of Rh and Co signals (g), their line profiles (h) along the dotted line in g and photocarrier migration probability towards the P or B facets (i). All crystals are imaged along the a orientation. The right panel presents schematic illustrations of the distribution patterns of electron and hole probes on the crystal surface. Photodeposition was conducted in a sequential manner, with CoO x deposited first, followed by Rh. On the PTI-E ⊥ crystal, Rh and Co signals are almost completely segregated onto different facets, indicating that out-of-plane migration is dominated by charge carriers (holes) rather than excitons. If exciton-mediated transport is operative, coupled electron–hole migration towards the B facet would result in co-deposition of Rh and CoO x on the B surface. Also, the uniform distribution of Rh signal along the P facet suggests rapid exciton dissociation in crystal bulk following their generation, supporting hole transport along the c-direction.
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