One-Dimensional-Sn2X3 (X = S, Se) as Promising Optoelectronic and Thermoelectronic Materials: A Comparison with Three-Dimensional-Sn2X3.

Ever since the discovery of two-dimensional (2D) material graphene, there has been huge interest in the exploration of low-dimensional materials that can be exfoliated from their three-dimensional counterpart with enriched properties due to quantum confinement. Two members of the Sn-S family, Pnma-SnS and P3̅ m1-SnS2 that possess a layered structure with 2D nanosheets stacked via weak van der Waals (vdW) interactions, have widely been studied in this regard. The other member, Pnma-Sn2S3, comprising one-dimensional (1D) nanochains bound via vdW interactions, has never been investigated in the view of exfoliated 1D analogue. In this work, we therefore comprehensively studied 1D-Sn2X3 (X = S and Se) nanochains and demonstrated them to be stable and exfoliable from their bulk counterpart. Further, it is also shown that the exfoliated 1D nanochains can easily be identified from their bulk counterpart using Raman, infrared, and X-ray spectroscopies. Our calculations predict a direct band gap of 2.35 eV (1.67 eV) for 1D-Sn2S3 (1D-Sn2Se3) nanochains under the Heyd, Scuseria, and Ernzerhof functional, with a broad absorption region lying between 2 and 8 eV, lower reflection, high charge-carrier mobility with ambipolar characteristics, as well as a larger value of the Seebeck coefficient and a smaller value of the thermal conductivity, resulting in a better thermoelectric figure of merit. These interesting electronic, optical, transport, and thermoelectric properties make 1D-Sn2X3 nanochains a potential candidate for the application in future optoelectronic and thermoelectronic devices, in fact, better than three-dimensional (3D)-Sn2X3 for few of the applications. Moreover, 3D-Sn2Se3 is also investigated in detail in this work, which to the best of our knowledge has not been done before.