Optimization strategies for crystal orientation in antimony-based chalcogenide thin-film solar cells

Antimony chalcogenides are highly promising thin-film photovoltaic materials. However, their quasi-one-dimensional structure inherently causes severe transport anisotropy. The thermodynamically stable [hk0] horizontal orientation induces van der Waals barriers that hinder carrier transport, whereas the kinetically favorable [hk1] vertical orientation constructs efficient charge pathways and dangling-bond-free "benign grain boundaries". Focusing on the thermodynamic and kinetic competition mechanisms during film growth, this review systematically summarizes recent optimization strategies for inducing the [hk1] preferred orientation. Four core approaches are highlighted: solvent and precursor engineering, deposition parameter optimization, interface and substrate engineering, and post-treatment reconstruction. Finally, we delineate the "structure-process-performance" relationship and provide perspectives on deep-level defect passivation, heterojunction band engineering, and flexible, large-area applications, aiming to guide the fabrication of high-efficiency antimony-based solar cells approaching their theoretical limit.