Giant two- to five-photon absorption in CsPbBr2.7I0.3 two-dimensional nanoplatelets

CsPbBr2.7I0.3 two-dimensional (2D) nanoplatelets (NPs) with emission wavelengths of 469 nm and 527 nm were synthesized and characterized. Femtosecond transient absorption spectra revealed hot carrier cooling times of similar to 368 fs and similar to 438 fs for 469 nm and 527 nm 2D NPs, respectively. Importantly, the 2D NPs exhibit giant two-, three-, four-, and five-photon absorption cross-sections, reaching similar to 4.1 x 10(6) GM at 830 nm, similar to 2.3 x 10(-74) cm(6) s(2) photon(-2) at 1300 nm, 2.06 x 10(-104) cm(8) s(3) photon(-3) at 1600 nm, and 1.50 x 10(-136) cm(10) s(4) photon(-4) at 2200 nm, respectively, which are 3-8 orders of magnitude larger, compared to specially designed organic molecules. (c) 2019 Optical Society of America