Fig. 2: Differential transmission measurements on thin films.
From: Exciton dissociation in 2D layered metal-halide perovskites
Top row (a–d): sketches of the expected DT signal, assuming a gaussian lineshape for exciton absorption, in case of bleaching, blueshift, broadening and redshift, respectively. Middle row (e–g): DT spectra measured on PEA2PbI4 thin-films, integrated in the first picosecond (solid line) after the arrival of the pump optical pulse and in the 5-10 ps delay window (dotted lines), for excitation wavelengths of 1030 nm (e, resonant two-photon), 860 nm (f, non-resonant, two-photon) and 430 nm (g, non-resonant, one photon). Bottom row (h–j): DT spectrograms from which spectra e–g were extracted, respectively, with time axis in logarithmic scale. Excitation fluences are 5 mJ/cm2/pulse, 3 mJ/cm2/pulse and 4 μJ/cm2/pulse for 2-photon resonant, 2-photon non-resonant and 1-photon non-resonant, respectively.
