Two-Photon Pumped Amplified Spontaneous Emission and Lasing from Formamidinium Lead Bromine Nanocrystals

Formamidinium (FA) perovskites have exhibited outstanding optoelectronic properties in solar cells and light-emitting diodes. However, their development on nanolaser application have rarely been explored, especially the up-conversion lasing performance. Here, the two-photon pumped lasing from colloidal FA-perovskite nanocrystals (NCs) is realized at room temperature, which are prepared by a ligand-assisted reprecipitation strategy. These colloidal FAPbX₃ NCs exhibit high-quality cubic phase and tunable bright emission (from 433 to 667 nm). By tuning the ratio of the surface organic ligands, the morphology of FAPbBr₃ NCs can be transferred from quantum dots to nanoplatelets, consequently the emission can be tuned in 520–542 nm. In addition, the low-threshold amplified spontaneous emission (ASE) under both two- and one-photon excitations is demonstrated benefiting from the large two-photon absorption coefficient (0.76 cm/GW) and high optical net gain (480 cm^–1), indicating that FAPbX₃ NCs can be regarded as an excellent optical gain medium. The strong temperature-tolerent ASE action with a high characteristic temperature of 308 K indicates the weak requirements of heat management of FA-based devices. Finally, as we couple FAPbBr₃ into a hollow capillary tube, stable two-photon excited whispering-gallery-mode lasing is successfully achieved with a low threshold of ∼310 μJ/cm². Our findings suggest that FAPbX₃ NCs can act as excellent gain media for high-performance upconverted nanolasers toward optoelectronic application.