Dopant‐Engineered Enhancement of Third‐Harmonic Generation in 2D Hybrid Perovskites

Abstract Low‐dimensional hybrid lead halide perovskites hold strong potential for nonlinear optical (NLO) applications due to their structural diversity, quantum and dielectric confinement, and soft lattice dynamics. Here, a substantial enhancement in third‐harmonic generation (THG) efficiency of a 2D perovskite‐derivative system, PEA ₂ PbI ₄ (PEA = phenylethylammonium), achieved through targeted doping with Mn ²⁺ and Sb ³⁺ ions is demonstrated. THG measurements across a broad wavelength range (1320–1860 nm) show that doping increases THG intensity up to an optimal dopant concentration. Notably, a six fold enhancement is achieved with 1.2% Mn ²⁺ doping. This improvement is attributed to dopant‐induced mid‐gap defect states and surface modifications that enhance the third‐order nonlinear susceptibility (χ⁽ ³ ⁾) and modulate the laser‐induced damage threshold (LIDT). Maximum THG enhancement occurs near the excitonic resonance at 482 nm. Although doped samples exhibit reduced optical stability, the THG response remains polarization‐independent, indicating preserved symmetry. The comparable performance of Mn ²⁺ (isovalent) and Sb ³⁺ (heterovalent) dopants suggests that the enhancement is a general doping effect rather than dependent on dopant charge or spin. These findings highlight doping as an effective strategy to boost NLO efficiency in layered perovskite systems, offering a viable route for future optoelectronic and photonic device applications.