One-Dimensional Chains in Pentanary Chalcogenides A₂Ba₃Cu₂Sb₂S₁₀ (A = K, Rb, Cs) Displaying a Photocurrent Response

The discovery of new inorganic functional chalcogenides is of fundamental importance in structure chemistry and materials science. Herein, a new type of pentanary thioantimonates, A₂Ba₃Cu₂Sb₂S₁₀ (A = K, Rb, Cs), has been discovered by a solvothermal method at low temperature. These isostructural compounds belong to the monoclinic space group C2/m (No. 12) and comprise unique one-dimensional (1D) [Cu₂Sb₂S₁₀]^8- chains surrounded by discrete A⁺ and Ba²⁺ cations. Such a 1D chain structure is the first case of chalcogenides in the X/Cu/Sb/Q (X = cations; Q = chalcogen) system. The energy gaps range from 1.90 to 1.98 eV for A₂Ba₃Cu₂Sb₂S₁₀ (A = K, Rb, Cs) were obtained from the UV-visible reflectance spectroscopy. Moreover, Rb₂Ba₃Cu₂Sb₂S₁₀ displays an intriguing photocurrent response under simulated solar-light illumination. The theoretical calculations were also carried out to understand the interrelationship of the optical performance and electronic structure.