PL measurements

The PL was measured under one- and two-photon excitation conditions. For one-photon excitation, we used the light with a wavelength of 360 nm. A beta-barium borate crystal was used for frequency-doubling of the 720-nm light obtained from the femtosecond laser system and the OPA. For two-photon excitation, we used the 750-nm laser light obtained from the OPA. The PL emission from the MAPbCl₃ single crystal was collected using a 10× near-infrared objective (Mitutoyo) and recorded by a nitrogen-cooled charge-coupled device camera equipped with a monochromator (SP 2500, Princeton Instruments). The measurements were performed in air at room temperature.