High-pressure Response in Two-dimensional Perovskites with Fluorinated Organic Spacers

Abstract

Two-dimensional (2D) Organic-Inorganic halide perovskites (OIHP) have emerged as a potential replacement for its 3D counterpart in perovskite solar cells (PSC) due to its enhanced stability. However, the presence of the large organic spacer cation hinders the charge transport, which lowers the power conversion efficiency in 2D OIHP. A fluorine organic spacer, obtained by substituting a fluorine atom with a hydrogen atom in the benzene ring, has provided a solution by enhancing orbital interactions and charge transport within the inorganic layers and applying external pressure on the perovskite has shown to alter its structural and optoelectronic properties. These two areas have generated great interest as they could potentially create a new approach to dive deeper and generate a better understanding of the properties of 2D OIHP. However, these two areas have never been reported together. In this report, we demonstrated applying high pressure causes a significant bandgap narrowing in both perovskites. When a fluorine atom is substituted in (PEA)2PbI4, the intermolecular bonds between each molecule are stronger than without the presence of the fluorinated organic cation under the same pressure conditions for both the organic and inorganic framework of the perovskite. However, we also showcase that this substitution process does not significantly affect the bandgap of the perovskite.