Semiconducting perovskites (2-XC6H4C2H4 NH3)2Snl4 (X = F, Cl, Br): Steric interaction between the organic and inorganic layers
Abstract
Two new semiconducting hybrid perovskites based on 2-substituted phenethylammonium cations, (2-XC6H4C2H4- NH3)2Snl4 (X = Br, Cl), are characterized and compared with the previously reported X = F compound, with a focus on the steric interaction between the organic and inorganic components. The crystal structure of (2-ClC6H4C2H4- NH3)2Snl4 is solved in a disordered subcell [C2/m, a = 33.781(7) Å, b = 6.178(1) Å, c = 6.190(1) Å, β = 90.42(3)°, and Z =2]. The structure is similar to the known (2-FC6H4C2H4N H3)2Snl4 structure with regard to both the conformation of the organic cations and the bonding features of the inorganic sheet. The (2-BrC6H4C2H4N H3)2-Snl4 system adopts a fully ordered monoclinic cell [P21/c, a = 18.540(2) Å, b = 8.3443(7) Å, c = 8.7795(7) Å, β = 93.039(1)°, and Z = 2]. The organic cation adopts the anti conformation, instead of the gauche conformation observed in the X = F and Cl compounds, apparently because of the need to accommodate the additional volume of the bromo group. The steric effect of the bromo group also impacts the perovskite sheet, causing notable distortions, such as a compressed Sn-I-Sn bond angle (148.7°, as compared with the average values of 153.3 and 154.8° for the fluoro and chloro compounds, respectively). The optical absorption features a substantial blue shift (lowest exciton peak: 557 nm, 2.23 eV) relative to the spectra of the fluoro and chloro compounds (588 and 586 nm, respectively). Also presented are transport properties for thin-film field-effect transistors (TFTs) based on spin-coated films of the two hybrid semiconductors.