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

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, PEA₂PbI₄ (PEA = phenylethylammonium), achieved through targeted doping with Mn²⁺ and Sb³⁺ 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% Mn²⁺ 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 Mn²⁺ (isovalent) and Sb³⁺ (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.