Importance of the Organic Component in the Layered Perovskite Semiconductors*

As next-generation semiconductors, hybrid perovskites with tailorable optoelectronic properties are critical for applications. In comparison to the3D counterparts, 2D perovskites exhibit improved moisture stability, the naturally formed quantum-well structure, and extended chemical engineering possibilities. Tunability lies on several factors: variable compositions, crystal structure where the spatial arrangement of halide octahedra has a great influence on the assembly behavior and materials properties; the organic molecules whose main function is to stabilize the perovskite materials through their interactions with the inorganic components. The optical properties are mainly contributed by the inorganic sublattice, while the importance of the organic component is more complex and requires further investigation. In this work, we discuss how the properties of 2D perovskites are dependent on the nature of the organic cations. By utilizing optical and vibrational spectroscopy in a wide temperature and pressure range, we demonstrate how various modifications of the organic groups bring up specific phenomena, such as disorder, in-plane anisotropy, response to extreme pressure.