Interfacial engineering is an important aspect for the development of high-efficiency photoelectric devices. The microscopic interplay between lattice distortion and carrier transport remains poorly understood. This study utilizes constrained density functional theory (CDFT+$U$) and Marcus theory to bridge this gap, using the anatase (101)/(001) interface as an example to investigate charge separation with a particular focus on the role of polarons. We find that while the interface undergoes distortion of the interfacial structure, both electron and hole polarons strongly localize with trapping energies of −0.48 eV and −0.97 eV, respectively. Quantitative analysis via crystal field theory reveals that the polaron stability is governed by the magnitude of orbital splitting (up to 4.47 eV for electrons and 3.86 eV for holes), which dictates a spatial disparity where both carriers initially favor the (001) side. However, dynamic transport simulations uncover an asymmetric kinetic steering mechanism that overrides these static energy preferences: Electron migration: Electrons exhibit a hierarchical transport pathway, initial intraplane diffusion followed by interface-guided migration, resulting in mobility toward the (101) side that is higher than toward the (001) bulk. Hole migration: Holes generated on the (101) side follow a cascaded mechanism, preferentially penetrating the interface to settle on the (001) side. By demonstrating that efficient charge separation is a product of electronic coupling and reorganization energy rather than mere spatial distribution, this work provides a predictive framework for optimizing photocatalytic efficiency through polaron-aware interface design.

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• Polarons
• Surface & interfacial phenomena
• Transport phenomena
• Heterostructures
• Transition metal oxides
• Density functional calculations