The emergence of two-dimensional (2D) materials has created new opportunities for engineering electronic, optical, and structural properties at the atomic scale. Among these materials, organic–inorganic hybrid perovskites (HOIPs) have attracted significant attention due to their unique combination of inorganic framework functionality and organic molecular tunability.

In contrast to their three-dimensional counterparts, 2D HOIPs can intrinsically exhibit enhanced quantum confinement, reduced dielectric screening, and highly tunable excitonic behavior, enabling superior performance in a range of optoelectronic applications. Although a lot of reported 2D HOIPs rely on the 2D confinement by organic-inorganic layer distinction, they are physically “bulk” in nature with multiple layers stacked. In this work, we explore the potential of isolated ultrathin 2D HOIPs, even to the monolayer regime achieved directly during the synthesis [1], as substitutes for conventional “bulk” 2D HOIPs.

We present a Copper-Manganese-Chloride (Cu-Mn-Cl) double perovskite where Phenethylamine (PEA) is the spacer, with varying ratio of Cu: Mn (PEA₂Cu_xMn_1-xCl₄). Starting from the pure Mn HOIP(x=0), the x is varied till pure Cu (x=1) HOIP is realized. The varying ratio varies the number of inorganic octahedra in the 2D layer with Cu (and Mn) in the center and thereby the band structure and optical properties. Investigations using temperature-dependent Raman spectroscopy, photoluminescence (PL), and time-resolved photoluminescence (TRPL) provided valuable insights into the optical properties of the samples and their evolution with varying Cu:Mn ratios [2]. Interestingly, low-temperature Raman measurements revealed well-resolved vibrational spectra with distinct signatures of the Cu:Mn ratio, whereas the low-temperature PL emission energy exhibited only weak dependence on the composition. However, as the temperature increased to room temperature, the evolution of the emission energy followed distinct trends, suggesting changes in the underlying emission mechanism. These observations were further corroborated by the TRPL measurements. In addition, it shows potential for further tuning by varying the number of layers, applying pressure, introducing an electric field etc. Hence, we will present an in-depth study towards its potential as a dynamically tunable ultrathin system.

Our results demonstrate that ultrathin 2D HOIPs offer significant advantages over bulk materials, by compatibility with flexible substrates, and opportunities for device miniaturization. These characteristics position them as promising candidates for next-generation photovoltaics, LEDs, photodetectors, and integrated nanoelectronics. The perspective presented contributes to the broader understanding of structure to property relationships in low dimensional hybrid materials and supports their development as versatile systems for future sustainable technologies.

[1] Kalyanasundaram et al (Manuscript under preparation)

[2] Gopalakrishnan et al (Manuscript under preparation)