Tailoring Optoelectronic Properties of 2D Perovskites through Molecular Engineering

Low-dimensional hybrid organic-inorganic perovskites are semiconducting materials with outstanding optoelectronic properties for applications in solar energy, light emission, lasing, etc. The structure consists of inorganic low-dimensional layers, rods or quantum dots, separated by bulk organic molecules. The near-band gap bands are normally determined by the inorganic lead halide component, however, the importance of the organic component should not be underestimated.

In our work, we demonstrate the effect of the organic component on the optoelectronic properties of two-dimensional (2D) perovskites. Long flexible aliphatic molecules are apt to conformational transitions, affecting the lead iodide layers and thus the optoelectronic properties. Under high pressure, such 2D perovskite creates micrometre-scale band gap junctions that can be applied in novel optoelectronic devices. In contrast, short rigid bi-cation distorts the perovskite octahedra arrangement into corrugated layers with in-plane anisotropic properties; including excitons-phonon coupling, charge transfer, and photoluminescence energy. Substitution of organic hydrogen atoms by halogens such as fluorine or bromine improves moisture stability and, in some cases, switches the conformation of the molecule. Finally, if the organic component is a dye, it directly contributes to the optoelectronic properties, while the perovskite can be considered as a natural semiconductor heterostructure.