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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) PL spectraof the CsPb(Br:X)3 (X = Cl, I) NCs preparedby anion exchange from CsPbBr3 NCs. (B) PL calibrationcurves: a targeted emission energy could be obtained by adding a preciseamount of halide precursor to a crude solution of CsPbBr3 NCs. The curves are reported as a function of the molar ratio betweenthe added halide (or exchange halide) and the Br amount in the startingNCs. (C) PLQY recorded on the exchanged NCs (dots) as well as on thedirectly synthesized NCs (stars).
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fig2: (A) PL spectraof the CsPb(Br:X)3 (X = Cl, I) NCs preparedby anion exchange from CsPbBr3 NCs. (B) PL calibrationcurves: a targeted emission energy could be obtained by adding a preciseamount of halide precursor to a crude solution of CsPbBr3 NCs. The curves are reported as a function of the molar ratio betweenthe added halide (or exchange halide) and the Br amount in the startingNCs. (C) PLQY recorded on the exchanged NCs (dots) as well as on thedirectly synthesized NCs (stars).

Mentions: All the anion exchange reactions discussed here led eitherto ablue shift (for the Br– → Cl– and I– → Br– routes)or to a red shift (for the Br– → I– and Cl– → Br– routes)of the optical features (Figure 1A and 1B), corroborating theincorporation of the new anions. Highly soluble precursors such asOLAM-X and TBA-X led to anion exchange within a few seconds (see Supporting Movies) at room temperature, and couldbe easily tracked by monitoring changes in the optical absorptionand PL spectra of the NCs (later discussed in Figure S1 and Figure 2A, respectively). The exchange with the less soluble ODA-Xand lead halides (PbX2) salts was generally slower andrequired instead at least 1 day under stirring to record a full shiftin the PL. Furthermore, exchange was often incomplete in such cases(broadened PL spectra were recorded). This could be easily explainedby the low solubility of these compounds in the relatively nonpolarTOL environment. Attempts to improve their solubility, by workingat 90 °C, resulted in quick degradation of the NCs (see alsolater).


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) PL spectraof the CsPb(Br:X)3 (X = Cl, I) NCs preparedby anion exchange from CsPbBr3 NCs. (B) PL calibrationcurves: a targeted emission energy could be obtained by adding a preciseamount of halide precursor to a crude solution of CsPbBr3 NCs. The curves are reported as a function of the molar ratio betweenthe added halide (or exchange halide) and the Br amount in the startingNCs. (C) PLQY recorded on the exchanged NCs (dots) as well as on thedirectly synthesized NCs (stars).
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4543997&req=5

fig2: (A) PL spectraof the CsPb(Br:X)3 (X = Cl, I) NCs preparedby anion exchange from CsPbBr3 NCs. (B) PL calibrationcurves: a targeted emission energy could be obtained by adding a preciseamount of halide precursor to a crude solution of CsPbBr3 NCs. The curves are reported as a function of the molar ratio betweenthe added halide (or exchange halide) and the Br amount in the startingNCs. (C) PLQY recorded on the exchanged NCs (dots) as well as on thedirectly synthesized NCs (stars).
Mentions: All the anion exchange reactions discussed here led eitherto ablue shift (for the Br– → Cl– and I– → Br– routes)or to a red shift (for the Br– → I– and Cl– → Br– routes)of the optical features (Figure 1A and 1B), corroborating theincorporation of the new anions. Highly soluble precursors such asOLAM-X and TBA-X led to anion exchange within a few seconds (see Supporting Movies) at room temperature, and couldbe easily tracked by monitoring changes in the optical absorptionand PL spectra of the NCs (later discussed in Figure S1 and Figure 2A, respectively). The exchange with the less soluble ODA-Xand lead halides (PbX2) salts was generally slower andrequired instead at least 1 day under stirring to record a full shiftin the PL. Furthermore, exchange was often incomplete in such cases(broadened PL spectra were recorded). This could be easily explainedby the low solubility of these compounds in the relatively nonpolarTOL environment. Attempts to improve their solubility, by workingat 90 °C, resulted in quick degradation of the NCs (see alsolater).

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.