Vertically Aligned One-Dimensional Crystal-Structured SbSe for High-Efficiency Flexible Solar Cells Regulating Selenization Kinetics.

Recently, antimony selenide (SbSe) 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 SbSe with a strong anisotropy in carrier transport and a lasting mechanical deformation tolerance. The control of the crystalline orientation of the SbSe film is an essential requirement for its device performance optimization. However, the current state-of-the-art SbSe 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 SbSe 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 SbSe film, a high efficiency of 8.42% with a record open-circuit voltage () of 0.47 V is obtained for flexible SbSe 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 SbSe film and promotes the formation of the MoSe interlayer between Mo and SbSe. These phenomena contribute to a back-surface field enhanced absorber layer and a quasi-Ohmic back contact, improving the device's and the collection of carriers. This method provides an effective strategy for the orientation control of 1D materials for efficient photoelectric devices.