Vertically Aligned One-Dimensional Crystal-Structured Sb₂Se₃ for High-Efficiency Flexible Solar Cells via Regulating...

Recently, antimony selenide (Sb₂Se₃) has exhibited an exciting potential for flexible photoelectric applications due to its unique one-dimensional (1D) chain-type crystal structure, low-cost constituents, and superior optoelectronic properties. The 1D structure endows Sb₂Se₃ with a strong anisotropy in carrier transport and a lasting mechanical deformation tolerance. The control of the crystalline orientation of the Sb₂Se₃ film is an essential requirement for its device performance optimization. However, the current state-of-the-art Sb₂Se₃ devices suffer from unsatisfactory orientation control, especially for the (001) orientation, in which the chains stand vertically. Herein, we achieved an unprecedented control of the (001) orientation for the growth of the Sb₂Se₃ film on a flexible Mo-coated mica substrate by balancing the collision rate and kinetic energy of Se vapor particles with the surface of Sb film by regulating the selenization kinetics. Based on this (001)-oriented Sb₂Se₃ film, a high efficiency of 8.42% with a record open-circuit voltage (V_OC) of 0.47 V is obtained for flexible Sb₂Se₃ solar cells. The vertical van der Waals gaps in the (001) orientation provide favorable diffusion paths for Se atoms, which results in a Se-rich state at the bottom of the Sb₂Se₃ film and promotes the in situ formation of the MoSe₂ interlayer between Mo and Sb₂Se₃. These phenomena contribute to a back-surface field enhanced absorber layer and a quasi-Ohmic back contact, improving the device's V_OC and the collection of carriers. This method provides an effective strategy for the orientation control of 1D materials for efficient photoelectric devices.