Antimony selenide (Sb2Se3) is a promising light-absorbing material for thin-film photovoltaics. Herein, we report a strategy for the fabrication of flexible Sb2Se3 solar cells on metal-foil substrates. A thin absorber grown on Mo foil exhibited poor performance owing to structural defect formation caused by the rough substrate. Although thicker films (∼1600 nm) are generally expected to suffer from high internal resistance, we found that unique vertical void formation enabled efficient charge transport, resulting in high-performance devices. Furthermore, oxide removal via NaOH treatment and the introduction of a preformed MoSe2 interlayer promoted the preferred [hk1] orientation and optimized the back contact. This dual modification simultaneously improved the film morphology and electronic properties, forming a pseudo-3D p-n junction that enhanced carrier collection. Consequently, the flexible co-evaporated Sb2Se3 solar cells achieved a power conversion efficiency of 4.45%. These findings provide mechanistic insights and practical guidelines for the design of high-performance flexible Sb2Se3 photovoltaics.
