摘要
Herein we report on the synthesis, crystal structure, vibrational and optoelectronic properties as well as DFT calculations of the air stable lead free TMS3M2I9 (TMS = (CH3)3S; M = Bi, Sb) perovskite halides. These compounds were synthesized with high purity using solid-state and solution methods by reacting MI3 and (CH3)3SI. Hexagonal, P63mc (No. 186), crystal structures of both compounds were confirmed at 393 K by single crystal X-ray Scattering and Rietveld analysis with a 0D network of [M2I9]3- dimer structure. TMS3M2I9 hexagonal undergoes structural phase transitions to the monoclinic crystal, twinning in the space group C121 (#5), at room temperature of 298 K. Investigation of lattice and molecular vibrations performed by Raman spectroscopy in the temperature range of −190–180 °C indicated the presence of hexagonal and monoclinic phases and confirmed the robustness of the synthesized materials related to the high stability of the trimethyl sulfonium cation in the perovskite framework. Band gaps of 2.1 eV and 2.3 eV were experimentally determined for the Bi- and Sb-containing perovskites, respectively. First-principles calculations were conducted to assess the energy band gap values, electronic structure, and density of states, yielding results consistent with the experimentally determined values. The new compounds were successfully incorporated in DSSCs, justifying their broad application potential. © 2025 Elsevier B.V.
