Multiphoton Absorption of 2D/3D Hybrid Metal Halide Heterojunctions

Hybrid metal halide (HMH) heterojunctions have been widely studied due to their unique quantum well structures and excellent optical properties. In this work, two kinds of 2D/3D HMH heterojunctions have been constructed, i.e., (S-2-NEA)2PbBr4/MAPbBr3 (S-MA) and (S-2-NEA)2PbBr4/FAPbBr3 (S-FA). By using femtosecond-transient absorption spectroscopy, it is revealed that S-MA has a more efficient energy transfer efficiency compared to S-FA. Based on the measurement of temperature-dependent photoluminescence spectra, it is confirmed that the S-MA exhibits stronger electron–phonon (EP) coupling strength than that of the S-FA film. As a result of more efficient energy transfer and stronger EP coupling strength, S-MA exhibits two- and three-photon absorption coefficients larger than those of S-FA. This work highlights the synergistic role of energy transfer and EP coupling in enhancing multiphoton absorption, providing crucial insights for designing HMHs with superior nonlinear optical properties.