Mixed‐Valence‐Driven Quasi‐1D Sn^IISn^IVS₃ with Highly Polarization‐Sensitive UV–vis–NIR Photoresponse

Abstract Mixed‐valence states can bring unexpected unique phenomena, especially novel anisotropic physics, due to structural asymmetry, which originate from the discrepant distribution of atoms with different valence. This study reports an unexploited mixed‐valence‐driven quasi‐1D Sn^IISn^IVS₃ crystal, which exhibits widely and distinctively anisotropic polarized‐light absorption reaching ≈3.4 from the deep ultraviolet to near‐infrared region (250–850 nm). The fabricated polarization‐sensitive photodetectors based on highly air‐stable Sn^IISn^IVS₃ nanowires display strong linear dichroism among the UV–vis–NIR spectrum with responsivity exceeding ≈150 A W⁻¹. Furthermore, the devices are further constructed onto a flexible polyethylene terephthalate (PET) substrate and the photoresponse remains roughly unchanged after repeated bending. This work based on novel mixed‐valence‐driven quasi‐1D ternary sulfide Sn^IISn^IVS₃ excites interest in low‐symmetry semiconductors for developing broadly spectral polarization‐sensitive photodetectors with environmental stability and mechanical flexibility.