Application of Voronoi Polyhedra for Analysis of Electronic Dimensionality in Emissive Halide Materials

The synthesis of new hybrid halide materials is attracting increasing research interest due to their potential optoelectronic applications. However, general design principles that explain and predict their properties are still limited. In this work, we attempted to reveal the role of intermolecular interactions on the optical properties in a series of hybrid halides with an (EtnNH4–n)2Sn1–xTexCl6(n= 1–4) composition. DFT calculations showed that the dispersions of the bands involving the Te 5s orbital character gradually decrease as the size of the organic cation increases, indicating a reducing orbital overlap between neighboring TeCl62–complexes. We characterized the photoluminescence (PL) of the Sn/Te solid solutions in (EtnNH4–n)2Sn1–xTexCl6(n= 1–4) phases to correlate the electronic and optical properties. The PL response shows no concentration quenching effects in the (Et4N)2Sn1–xTexCl6series, which demonstrated electronically isolated TeCl62–complexes. However, the series with smaller organic cations (n= 1–3) and higher electronic dimensionality show concentration quenching effects, which decrease as a function of the Te 5s band dispersions in these compounds. Similar trends can be revealed using a simple semiquantitative electronic dimensionality analysis method by means of Voronoi polyhedra. Since this approach relies only on structural data, it enables rapid characterization of orbital overlap between metal halide complexes in hybrid materials without DFT calculations. The present results allow us to conclude that electronic dimensionality plays an essential role in the photophysical properties of hybrid halide compounds and can be used to fine-tune their properties.