Critical Review on Crystal Orientation Engineering of Antimony Chalcogenide Thin Film for Solar Cell Applications

The emerging antimony chalcogenide (Sb₂ (S_x Se_1-x )₃ , 0 ≤ x ≤ 1) semiconductors are featured as quasi-1D structures comprising (Sb₄ S(e)₆ )_n ribbons, this structural characteristic generates facet-dependent properties such as directional charge transfer and trap states. In terms of carrier transport, proper control over the crystal nucleation and growth conditions can promote preferentially oriented growth of favorable crystal planes, thus enabling efficient electron transport along (Sb₄ S(e)₆ )_n ribbons. Furthermore, an in-depth understanding of the origin and impact of the crystal orientation of Sb₂ (S_x Se_1-x )₃ films on the performance of corresponding photovoltaic devices is expected to lead to a breakthrough in power conversion efficiency. In fact, there are many studies on the orientation control of Sb₂ (S_x Se_1-x )₃ colloidal nanomaterials. However, the synthesis of Sb₂ (S_x Se_1-x )₃ thin films with controlled facets has recently been a focus in optoelectronic device applications. This work summarizes methodologies that are applied in the fabrication of preferentially oriented Sb₂ (S_x Se_1-x )₃ films, including treatment strategies developed for crystal orientation engineering in each process. The mechanisms in the orientation control are thoroughly analyzed. An outlook on perspectives for the future development of Sb₂ (S_x Se_1-x )₃ solar cells based on recent research and issues on orientation control is finally provided.