was estimated using the XPS valence band maxima (Figure ). The band gap of TiO2, taken from the literature, is 3.2 eV. With these values, the energy band alignments of the Sb2Se3/TiO2 heterojunction for both devices were constructed before contact, as seen in Figure . The energy band bending of the Sb2Se3/TiO2 heterojunction obtained after EF equilibration is presented in Figure . It revealed that a slightly larger band bending formed in the Sb2Se3-H photocathode compared with the Sb2Se3-L photocathode. This indicates that photoexcited electrons can be more efficiently extracted in the Sb2Se3-H photocathode at the same biased potential. In addition, the crystal structure has negligible influence on the PEC performance since both Sb2Se3 samples have identical crystal orientations. However, the morphology displays a big difference between the Sb2Se3-H and Sb2Se3-L samples. For the Sb2Se3-H thin film, it has longer and thinner nanorods compared to the Sb2Se3-L thin film. Due to the anisotropic properties of Sb2Se3, electron mobilities vary, making it easier for photoexcited electrons to transport along (Sb4Se6)n ribbons connected by covalent bonds, while it is more difficult to cross ribbons bonded by van der Waals forces. Based on these morphological differences and the anisotropy in charge carrier mobility, a charge transport mechanism was proposed. The photoexcited electrons in the Sb2Se3 bulk must be transported to the