Two-photon absorption spectroscopy of 2D and 3D hybrid perovskites

We provide a unique perspective on the dependence of the electronic structure of various phases of organic lead-halide perovskites through spectrally resolved non-linear optical coefficient. In particular, we compare crystals of MAPbX₃ (X = Br and I) at different temperatures and macroscopic crystals of the layered, 2D lead-halide phase trough two-photon photoluminescence excitation spectroscopy in combination with other methods for determining the two-photon absorption (TPA) coefficient. The assignment of features is aided through electroabsorption spectroscopy and calculation of the TPA spectrum from the band structure. Comparison of photoluminescence under one-photon and two-photon excitations allows separation of surface and bulk properties. These interesting features are thus extremely useful for understanding the bulk electronic properties of many hybrid perovskites and may guide their further development for non-linear optics and optoelectronic technology.