Great Second‐Harmonic Generation Enhancement in Transition Metal Dichalcogenides by Resonance Energy Transfer from Ruddlesden–Popper Perovskites

Abstract Ruddlesden–Popper perovskites (RPPs) exhibit intrinsic quantum well structures and exceptional photoelectric properties, including superior light absorption characteristics and efficient carrier transport capabilities. These properties have garnered significant interest in their applications in light‐emitting diodes, sensors, and photovoltaics. Nevertheless, most of these applications remain within the realm of linear optics, leaving the vast potential of RPPs in nonlinear optics relatively unexplored. In this study, it is demonstrated that van der Waals stacking between transition metal dichalcogenides and RPPs enables a remarkable near two‐order‐of‐magnitude enhancement in second harmonic generation (SHG). Through systematic investigation, it is revealed that this enhanced SHG arises from nonlinear resonance energy transfer (ET) facilitated by long‐range dipole–dipole coupling. Importantly, the SHG enhancement can be effectively modulated by controlling the thickness of RPP layers. Furthermore, this ET‐mediated SHG enhancement is not limited to specific combinations but is a general phenomenon observed in heterostructures involving RPPs and various 2D materials. This work provides a practical approach to achieving scalable and uniform enhancement of nonlinear optical responses in 2D materials, opening a promising avenue for the development of high‐performance, multifunctional nonlinear photonic nanodevices.