2D Ruddlesden–Popper Perovskites with a Thick Octahedral Layer (n = 7) as a Robust Alternative for Energy-Related Application

Abstract

Halide perovskites have led to outstanding optoelectronic performance, even though their operational stability, especially for 3D MAPbI₃, persists as a critical obstacle. Here, we synthesize a Ruddlesden–Popper iodide series (n = 1, 2, and 7) using a butylammonium spacer and directly compare the thick-layer member (n = 7; hereafter termed quasi-3D) with 3D MAPbI₃. Structural and morphological analyses confirm a progressive evolution toward 3D-like character with increasing n (octahedral sheets), while steady-state optical measurements show that the n = 7 phase exhibits an emission energy close to MAPbI₃. Crucially, in situ diamond-anvil-cell photoluminescence under hydrostatic pressure reveals markedly different flexibility: MAPbI₃ undergoes strong PL quenching at lower pressure and shows incomplete spectral recovery upon decompression, whereas the quasi-3D phase sustains emission to substantially higher pressures and displays reversible PL restoration after pressure release. Complementary surface measurements show enhanced hydrophobicity for the quasi-3D sample, and electrical conductivity demonstrates a comparable light-induced photoconductivity response to that of MAPbI₃. Our results suggest that thick-layer (n = 7) Ruddlesden–Popper perovskites are a promising route to improve chemical and mechanical stability while preserving 3D-like optoelectronic functionality for energy-related devices.