Organic-inorganic hybrid low-dimensional perovskites are attracting significant attention for optoelectronic applications due to their higher stability, uncomplicated manufacturing process, and wide tunability of the optical and electronic properties. The use of various organic cations leads to the formation of two-dimensional (2D) layers, one-dimensional (1D) chains, or isolated zero-dimensional (0D) clusters depending on how the metal halide octahedra are connected. Even minimal differences in the structure of the organic cations can cause remarkable changes in the structural arrangement and, as a consequence, a modification of the optoelectronic properties of the perovskite system.

The incorporation of functionalized ammonium cations in perovskites allows the design of a variety of new organic-inorganic hybrid materials, in which functionalized and even semiconducting organic layers are assembled with a semiconducting inorganic layer at the molecular scale. In recent works devoted to low-dimensional inorganic-organic halide perovskites much attention has been paid to the broadband emission properties primarily originating from the self-trapped excitons (STEs) [1,2]. High structural distortion of low-dimensional perovskite structures induces electron-phonon coupling and enhances the STE process, resulting in an enhanced broadband emission. In addition, it has been demonstrated that perovskites grown in a form of atomically thin sheets possess unique features compared to their bulk counterparts [3]. For example, hybrid perovskite sheets exhibit an unusual structural relaxation, which leads to a band gap shift. Consequently, the controllable synthesis of ultrathin perovskite sheets has gained a great research interest for implementation in high-performance optoelectronic devices.

In this work, a series of low-dimensional hybrid organic-inorganic metal halides, based on multiple-ring aromatic ammonium cations and lead iodide were fabricated and their structures and properties were investigated. Examination of the influence of organic cations on the structural properties reveals that the number and position of amino groups at the aromatic ring affect the dimensionality of the perovskite, resulting in 2D and 1D corner- and face-sharing structures with different optical behavior. Highly distorted 1D perovskites show broadband emissions originating from STEs. Theoretical results reveal, that the organic cations in the 1D compounds strongly contribute to the band structure resulting in strong orbitals hybridization. Using a facile and fast crystallization method we also synthesized organic-inorganic hybrid perovskite few-layer free-standing nanosheets containing the naphthalene diammonium-based linker. Varying the synthetic conditions, we can modulate the thickness and lateral sizes of the nanosheets.