Engineering Chalcogenide-Containing Spacers: Modulating Internal Interactions for Enhanced Performance and Stability in Ruddlesden–Popper Perovskite Devices

Two-dimensional (2D) Ruddlesden–Popper (RP) halide perovskites are promising for optoelectronic applications due to their enhanced stability compared to 3D versions. However, their practical application is still hindered by the inherent instability arising from weak interactions between adjacent organic layers. To address this challenge, we engineered 2D RP perovskites using four organic spacers: 3-thiophene-methylammonium (3-TMA) and 3-furan-methylammonium (3-FMA), with 2-thiophene-methylammonium (2-TMA) and 2-furan-methylammonium (2-FMA) as controls. Our findings highlight that the heteroatom type (S vs O) and spacer regiochemistry significantly influence interaction strength. Thiophene-based spacers bond more robustly to inorganic layers than furan-based ones. Notably, shifting the thiophene spacer configuration from 2-TMA to 3-TMA markedly strengthens interactions between organic layers, improving RP perovskite stability under ambient and thermal conditions. Utilizing the substantial dipole moment of the optimized 3-TMA spacer, we developed an enhanced performance perovskite photodetector with a responsivity of 153 mA/W and detectivity of 1.7 × 10¹⁰ Jones. This study offers insights into RP perovskite stability and guides the design of durable perovskite devices through strategic spacer engineering.