Novel One-Dimensional Lead-Free Inorganic–Organic Semiconducting Materials Containing Antimony(III) Mixed-Halide Anions: From Synthesis to Structural and Optoelectronic Characterization

Abstract

Antimony(III) halide-based inorganic–organic perovskites have promising potential as emerging semiconducting materials with distinctive optoelectronic properties. Here, we report two new inorganic–organic materials containing novel mixed antimony halides that were synthesized by solvothermal reaction of antimony iodide with a haloacid, HX (X = Cl or Br), and 1,10-phenanthroline (Phen) or quinoxaline (Qx). The structures of both compounds were characterized by single-crystal X-ray diffraction at 100 K. The reaction of Phen and SbI3 with HCl led to the product (Phen-H)SbCl4.xIx•H2O (x = 0.12) (1), constructed of mixed polymeric haloanion units (SbCl3.88I0.12–)∞, with protonated cations (Phen-H+) and a water molecule of crystallization. Among the four crystallographically independent halide sites of the anion (SbCl3.88I0.12–), one site is occupied by Cl– and the remaining three are mixed-occupied by chloride and iodide ions. The reaction of Qx and SbI3 with HBr led to the salt (Qx-H)SbBr4.xIx (x = 1.87) (2), consisting of independent Qx-H+ cations and polymeric mixed haloanions (SbBr2.13I1.87–)∞, formed by edge-sharing SbX6 octahedra. The four crystallographically independent halides exhibit mixed occupations by bromide and iodide. The assembly of anionic chains and organic cations generates, for both compounds, supramolecular networks via numerous noncovalent interactions. Despite their low dimensionality, solid-state optical studies show that both compounds possess semiconducting properties due to their surprisingly small band gaps. Furthermore, these materials feature a strong temperature dependence of their photoluminescence (PL) along with long lifetimes (τ). The optical bandgap energies are affected by the halide contents, ranging from 2.08 eV for 1 to 1.92 eV for 2, which makes them promising candidates for optoelectronic devices. The bulk crystals of 1 and 2 exhibit broad dual-band emission, which originates from the radiative transitions of both free excitons (FE) and self-trapped excitons (STE) in the [SbX4– ]n chains. This is proven by the difference in their lifetimes (τ1 = 16.85 ns and τ2 = 82.65 ns for 1; τ1 = 6.09 ns and τ2 = 40 ns for 2). These developed materials also exhibit interesting thermochromic behavior, which expands the scope of developing multifunctional halometallates(III).