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Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions.

Akkerman QA, D'Innocenzo V, Accornero S, Scarpellini A, Petrozza A, Prato M, Manna L - J. Am. Chem. Soc. (2015)

Bottom Line: This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs.We also show that anion exchange is a dynamic process that takes place in solution between NCs.Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles.

View Article: PubMed Central - PubMed

Affiliation: †Nanochemistry Department, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.

ABSTRACT
We demonstrate that, via controlled anion exchange reactions using a range of different halide precursors, we can finely tune the chemical composition and the optical properties of presynthesized colloidal cesium lead halide perovskite nanocrystals (NCs), from green emitting CsPbBr3 to bright emitters in any other region of the visible spectrum, and back, by displacement of Cl(-) or I(-) ions and reinsertion of Br(-) ions. This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs. We also show that anion exchange is a dynamic process that takes place in solution between NCs. Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles.

No MeSH data available.


(A–C) TEM images of pristine CsPbBr3 NCs (B)and of fully exchanged CsPbCl3 (A) and CsPbI3 NCs (C), indicating overall size and size preservation upon anionexchange. Scale bars correspond to 50 nm. (D) Zoom of the XRD patternsof pristine CsPbBr3 NCs (middle pattern in green), of theanion exchanged CsPbCl3 (top, violet), CsPbI3 (bottom, red) and of two intermediate Cl– (middle-top,light blue) and I– (middle-bottom, yellow) exchangedsamples. Full XRD patterns are reported in Figure S9.
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fig3: (A–C) TEM images of pristine CsPbBr3 NCs (B)and of fully exchanged CsPbCl3 (A) and CsPbI3 NCs (C), indicating overall size and size preservation upon anionexchange. Scale bars correspond to 50 nm. (D) Zoom of the XRD patternsof pristine CsPbBr3 NCs (middle pattern in green), of theanion exchanged CsPbCl3 (top, violet), CsPbI3 (bottom, red) and of two intermediate Cl– (middle-top,light blue) and I– (middle-bottom, yellow) exchangedsamples. Full XRD patterns are reported in Figure S9.

Mentions: Anion exchange did not alter the cubic shape ofthe initial CsPbBr3 NCs (Figure 3D), although after exchange with Cl– their sizedecreased slightly, from (8.4 ± 1.0) nm to (8.0 ± 1.4) nm(Figure 3A), whereasthe exchange with I– led to a slight increase insize, to (9.1 ± 1.3) nm (Figure 3C; see also Figure S7 and S8). The XRD pattern collected on the pristine CsPbBr3 NCs(Figure 3D) could beindexed as cubic CsPbBr3 (a = 5.874 Å,space group Pm3̅m, ICSD 29073)as detailed in Figure S9, in agreementwith what reported by Protesescu et al.11 Anion exchange reactions did not alter the crystal phase of theNCs (see Figures 3D, S4B and S9) and the patterns collected on thealmost fully exchanged NCs were in good agreement with those recordedon directly synthesized CsPbI3 (a = 6.18Å, space group Pm3̅m,ICSD 181288) and CsPbCl3 (a = 5.605 Å,space group Pm3̅m, ICSD 29072)NCs. The XRD patterns of partially exchanged NCs too could be ascribedto the same cubic phase: as expected, upon incorporation of Cl–, the cell shrunk and all the peaks shifted to higherangles, while the incorporation of I– expanded thecell and the peaks shifted to lower angles (Figure 3D).


Tuning the Optical Properties of Cesium Lead Halide Perovskite Nanocrystals by Anion Exchange Reactions.

Akkerman QA, D'Innocenzo V, Accornero S, Scarpellini A, Petrozza A, Prato M, Manna L - J. Am. Chem. Soc. (2015)

(A–C) TEM images of pristine CsPbBr3 NCs (B)and of fully exchanged CsPbCl3 (A) and CsPbI3 NCs (C), indicating overall size and size preservation upon anionexchange. Scale bars correspond to 50 nm. (D) Zoom of the XRD patternsof pristine CsPbBr3 NCs (middle pattern in green), of theanion exchanged CsPbCl3 (top, violet), CsPbI3 (bottom, red) and of two intermediate Cl– (middle-top,light blue) and I– (middle-bottom, yellow) exchangedsamples. Full XRD patterns are reported in Figure S9.
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fig3: (A–C) TEM images of pristine CsPbBr3 NCs (B)and of fully exchanged CsPbCl3 (A) and CsPbI3 NCs (C), indicating overall size and size preservation upon anionexchange. Scale bars correspond to 50 nm. (D) Zoom of the XRD patternsof pristine CsPbBr3 NCs (middle pattern in green), of theanion exchanged CsPbCl3 (top, violet), CsPbI3 (bottom, red) and of two intermediate Cl– (middle-top,light blue) and I– (middle-bottom, yellow) exchangedsamples. Full XRD patterns are reported in Figure S9.
Mentions: Anion exchange did not alter the cubic shape ofthe initial CsPbBr3 NCs (Figure 3D), although after exchange with Cl– their sizedecreased slightly, from (8.4 ± 1.0) nm to (8.0 ± 1.4) nm(Figure 3A), whereasthe exchange with I– led to a slight increase insize, to (9.1 ± 1.3) nm (Figure 3C; see also Figure S7 and S8). The XRD pattern collected on the pristine CsPbBr3 NCs(Figure 3D) could beindexed as cubic CsPbBr3 (a = 5.874 Å,space group Pm3̅m, ICSD 29073)as detailed in Figure S9, in agreementwith what reported by Protesescu et al.11 Anion exchange reactions did not alter the crystal phase of theNCs (see Figures 3D, S4B and S9) and the patterns collected on thealmost fully exchanged NCs were in good agreement with those recordedon directly synthesized CsPbI3 (a = 6.18Å, space group Pm3̅m,ICSD 181288) and CsPbCl3 (a = 5.605 Å,space group Pm3̅m, ICSD 29072)NCs. The XRD patterns of partially exchanged NCs too could be ascribedto the same cubic phase: as expected, upon incorporation of Cl–, the cell shrunk and all the peaks shifted to higherangles, while the incorporation of I– expanded thecell and the peaks shifted to lower angles (Figure 3D).

Bottom Line: This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs.We also show that anion exchange is a dynamic process that takes place in solution between NCs.Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles.

View Article: PubMed Central - PubMed

Affiliation: †Nanochemistry Department, Istituto Italiano di Tecnologia, Via Morego 30, 16163 Genova, Italy.

ABSTRACT
We demonstrate that, via controlled anion exchange reactions using a range of different halide precursors, we can finely tune the chemical composition and the optical properties of presynthesized colloidal cesium lead halide perovskite nanocrystals (NCs), from green emitting CsPbBr3 to bright emitters in any other region of the visible spectrum, and back, by displacement of Cl(-) or I(-) ions and reinsertion of Br(-) ions. This approach gives access to perovskite semiconductor NCs with both structural and optical qualities comparable to those of directly synthesized NCs. We also show that anion exchange is a dynamic process that takes place in solution between NCs. Therefore, by mixing solutions containing perovskite NCs emitting in different spectral ranges (due to different halide compositions) their mutual fast exchange dynamics leads to homogenization in their composition, resulting in NCs emitting in a narrow spectral region that is intermediate between those of the parent nanoparticles.

No MeSH data available.