Visible-light photodetection by zero-dimensional hybrid indium-halide with minimal structural distortion and reduced band gap

Perovskite-inspired zero-dimensional (0D) hybrid halides exhibit impressive light emission properties; however, their potential in photovoltaics is hindered by the absence of interconnection between the inorganic polyhedra, leading to acute radiative recombination and insufficient charge separation. We demonstrate that incorporating closely-spaced dissimilar polyhedral units with minimal structural distortion leads to a remarkable enhancement in visible-light photodetection capability. We designed 0D C${}_{24}$H${}_{72}$N${}_8$In${}_2$Br${}_{14}$ (HIB) with a tetragonal crystal system, replacing the Cs${}^{+}$ of Cs${}_2$InBr${}_5$.H${}_2$O (CIB) with 1,6-hexanediammonium (HDA) cation. HIB comprises [InBr${}_6$]${}^{3-}$ octahedra, and [InBr${}_4$]${}^{-}$ tetrahedra units spaced 3.9 Å apart by the HDA linker. The [InBr${}_4$]${}^{-}$ unit is additionally linked to HDA via intercalated bromine through hydrogen and halogen bonding interactions, respectively. This structural arrangement lowers the dielectric confinement, thereby enhancing carrier density and mobility, and increasing the diffusion coefficient compared to CIB. With 3.6 % bromine vacancy within the [InBr${}_4$]${}^{-}$ block, mid-gap states are created, reducing the direct band gap to 2.19 eV. HIB demonstrates an unprecedently high responsivity of 9975.9±201.6 mA W${}^{-1}$ under 3 V potential bias at 485 nm wavelength, among low-dimensional hybrid halides. In the absence of potential bias, the self-powered photodetection parameters are 81.2±3.0 mA W${}^{-1}$ and (6.98±0.21)×10${}^9$ Jones. (© 2024 Wiley-VCH GmbH)