The Two-Photon Absorption Cross-Section Studies of CsPbX3 (X = I, Br, Cl) Nanocrystals

Abstract

The CsPbX3 nanocrystals (NCs) with X = I, Br, Cl, or the mixture of Br:I and Br:Cl in a 1:1 ratio were synthesized and characterized by TEM, DLS, and XRD. Recrystallization of the small luminescent NCs in the metastable cubic phase into bigger orthorhombic nanocrystals was monitored by XRD and identified as the main cause of the nanocolloid coagulation. The recrystallization also leads to a decrease in the photoluminescence quantum yield (QY) of the colloidal solution and shortening of the emission lifetime. The two-photon absorption cross-section σ2 values calculated from femtosecond Z-scan measurements were compared with those obtained based on the two-photon excited emission technique. These two techniques were shown to be equivalent with the cross-section values calculated per molar mass of CsPbX3 perovskite being in the range of 10–200 GM depending on the halide anions X−. The σ2 values recalculated for the mole of the NCs were in the range of 104–105 GM, which is in good agreement with values previously reported elsewhere and the σ2/M parameter was in the range of 0.01 to 0.33. This study shows the perovskite NCs to be a good nonlinear material with the third-order nonlinear optical susceptibility χ(3) of the NCs on the order of 10−11 esu.

Nonlinear Optical Properties of Emerging Nano‐ and Microcrystalline Materials

“…Our group recently investigated a similar set of perovskite nanomaterials. [51] A similar trend was noted for TPEF results for CsPbCl 1.5 Br 1.5 , CsPbBr 3 , CsPbBr 1.5 I 1.5 , see Table 1, entries 21, 2, and 27, respectively. According to these results, the best performing is perovskite CsPbBr 1.5 I 1.5 with σ 2 value of 1.6 ± 0.2 × 10 5 GM, whereas CsPbCl 1.5 Br 1.5 , CsPbBr 3 , NCs feature lower 2PA response (3.5 ± 0.7 × 10 4 GM and 1.0 ± 0.1 × 10 5 GM per NC, respectively).…”

“…Taking the two-photon absorption results as an example, the huge cross sections reported in the literature are not so impressive after being normalized to the molecular weight of the investigated species. Szeremeta et al [51] quoted σ 2 /M values in the range of 0.01 to 0.33 for perovskite nanoparticles, which is similar to the values obtained for many semiconductor NPs and notably less than the values exceeding unity obtainable for organometallic dendrimers [158] or plasmonic nanoparticles. [159] All in all, the feeling of the authors of this review is that we are at the very beginning of the research into this fertile field but, while many of the extant results need to be carefully scrutinized, it is beyond doubt that the newly emerging NLO materials may provide many interesting applications in the future.…”

“…Good demonstration of that is provided in our recent report, in which we studied 2PA spectra of CsPbX 3 perovskite NCs using the Z-scan and TPEF techniques. [51] We shall take CsPbBr 3 as an example.…”

Water Triggered Synthesis of Highly Stable and Biocompatible 1D Nanowire, 2D Nanoplatelet, and 3D Nanocube CsPbBr3 Perovskites for Multicolor Two-Photon Cell Imaging

“… 45 − 54 Experimental details have been reported before and are discussed in the Supporting Information . 47 , 55 , 58 − 60 , 68 − 71 In brief, for the measurement, we used an 80 MHz Ti-sapphire laser as an excitation source with 100 fs pulse width. 47 , 55 , 58 − 60 We used an optical parametric amplifier to generate 800 nm excitation wavelength.…”

Calculation of two-photon absorption by nanocrystals of CsPbBr3

“…Absorption by these NCs has also been studied extensively, including measurements of the one-photon [10][11][12][13][14], two-photon [10,[12][13][14][15][16][17], and up to five-photon [15] absorption spectra. Multiphoton absorption by NCs has important technological applications to three-dimensional (3D) biomedical imaging, as the absorption of several infrared photons with reemission at a shorter wavelength gives improved penetration depth and low biological damage, combined with good spatial confinement [18].…”