Replication Data for: Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes (doi:10.21979/N9/GAPRHL)

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Replication Data for: Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes

doi:10.21979/N9/GAPRHL

DR-NTU (Data)

2020-04-28

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Alasdair A. M. Brown; Thomas J. N. Hooper; Sjoerd A. Veldhuis; Xin Yu Chin; Annalisa Bruno; Parth Vashishtha; Ju Nie Tey; Liudi Jiang; Bahulayan Damodaran; Suan Hui Pu; Subodh G. Mhaisalkar; Nripan Mathews, 2020, "Replication Data for: Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes", https://doi.org/10.21979/N9/GAPRHL, DR-NTU (Data), V1

Replication Data for: Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes

doi:10.21979/N9/GAPRHL

Alasdair A. M. Brown (Nanyang Technological University)

Thomas J. N. Hooper (Nanyang Technological University)

Sjoerd A. Veldhuis (Nanyang Technological University)

Xin Yu Chin (Nanyang Technological University)

Annalisa Bruno (Nanyang Technological University)

Parth Vashishtha (Nanyang Technological University)

Ju Nie Tey (A*STAR)

Liudi Jiang (University of Southampton)

Bahulayan Damodaran (Nanyang Technological University)

Suan Hui Pu (University of Southampton)

Subodh G. Mhaisalkar (Nanyang Technological University)

Nripan Mathews (Nanyang Technological University)

Inkscape

Competitive Research Program (CRP Award No. NRF-CRP14-2014-03)

DR-NTU (Data)

Alasdair A. M. Brown

Alasdair A. M. Brown

2020-04-27

https://doi.org/10.21979/N9/GAPRHL

Chemistry, Physics, Chemistry, Physics, perovskite, nanocrystals, light emitting diode, NMR, ligand, surface chemistry

In this work we employ a post-synthetic ligand exchange treatment with octylphosphonic acid to substitute the native oleic acid ligands on cesium lead bromide nanocrystals. Using solid-state NMR we proved that the introduced octylphosphonic acid ligands bound to the nanocrystal surface in a monodentate mode, also forming inter-ligand hydrogen bonds through their free P=O and P-OH groups. The binding of this ligand improved surface passivation, increasing post-purification PLQY to 62 %. As a result, we were able to fabricate light-emitting diodes with a maximum external quantum efficiency of 7.74 %.

Figures

10.1039/C9NR02566A

Brown, A. A., Hooper, T. J., Veldhuis, S. A., Chin, X. Y., Bruno, A., Vashishtha, P., ... & Mhaisalkar, S. G. (2019). Self-assembly of a robust hydrogen-bonded octylphosphonate network on cesium lead bromide perovskite nanocrystals for light-emitting diodes. Nanoscale, 11(25), 12370-12380.

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13C_v4.png

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The 13C cross-polarisation magic-angle spinning (CPMAS) NMR spectra of crystalline OPA and TOPO, and each CsPbBr3 NC sample.

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1HNMR_v2-01.png

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Solution 1H NMR spectra of each CsPbBr3 NC solution. Asterisks (*) denote residual proton signals from the solvent (toluene-d8, toluene) and the antisolvents (ethyl acetate and acetonitrile). Observable broad resonances corresponding to protons in oleyl and octyl chains of the respective bound ligands (OLA/OA and OPA) are labelled.

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Figure 1.png

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CsPbBr3 NC characterization. (a) NC edge length distribution derived from small-angle X-ray scattering (SAXS). Inset: Photograph of OPA-2w CsPbBr3 NC dispersion (b) transmission electron microscopy image and (c) absorbance and PL spectra (λex = 365 nm), of an OPA-2w NC dispersion. Inset: Photograph of OPA-2w CsPbBr3 NC dispersion under UV illumination. (d) PL intensity maximum of a CsPbBr3 NC dispersion as a function of the concentration of octylphosphonic acid solution added. (e) PL peak intensity of CsPbBr3 NC toluene dispersions treated with low (3.86 mM/ 0.75 mg mL−1) and high (15.45 mM/3 mg mL−1) concentration OPA solutions before purification and after consecutive (1) 3 : 1 v/v ethyl acetate and (2) 1 : 1 v/v acetonitrile purification cycles. (f ) Time-resolved PL decays at λex = 405 nm of the 3 NC samples indicated by coloured circles in (e).

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Figure 2 Nanoscale.png

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31P–1H HETCOR ssNMR spectra of (a) crystalline OPA reference, (b) CsPbBr3 NCs treated with OPA after ethyl acetate and (c) acetonitrile purification cycles, and (d) unpurified CsPbBr3 NCs synthesized using OPA and TOPO. The 1D 31P MAS NMR spectrum is shown above each 2D HETCOR spectrum for comparison. Areas marked by have magnified contour levels to reveal the detail of lower intensity HETCOR resonances

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Figure 3.png

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CsPbBr3 NC LED device characteristics. (a) Band diagram, (b) current–voltage–luminance, (c) EQE/current efficiency against current density, and (d) power efficiency against luminance plots. CON denotes reference NC inks, OPA denotes OPA-treated inks; 1w and 2w denotes inks washed once (EtOAc) and twice (EtOAc, ACN), respectively.

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FTIR.png

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ATR FTIR spectra. (a) REF (solid) and OPA (dashed) NC samples for purified once (black) and twice (red). The C−O stretching region is shown. (b) Crystalline OPA (blue) and OPA NC samples after one purified cycle with 2:1 ethyl acetate (black) and after a second purification cycle with 1:1 acetonitrile (red). The P−O stretching region is shown.

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OPA binding mechanism 2.png

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Proposed attachment mechanism of octylphosphonic acid ligands to the surface of CsPbBr3 NCs (R = octyl, R’ =oleyl). The Pb–Br–Pb linkages represent corner sharing [PbBr6]4− octahedra of the perovskite lattice.

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PL Stability updated.png

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Photoluminescence spectra of (a) OPA−2w and (b) REF−2w CsPbBr3 NC solutions (concentration ≈ 0.05 mg mL-1) monitored over time. Insets show magnified sections of the same spectra at the emission maximum.

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Purification scheme.png

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The purification and ligand exchange protocol employed herein. The green, blue and red arrows represent the NC isolation (0w), 1st purification (1w) and 2nd purification (2w) cycles, respectively. Also shown are the stages of the cycles at which precipitated samples were extracted for solid-state NMR analysis, and NC inks were extracted for optical analysis and LED fabrication.

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Scheme 2.png

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TGA.png

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Thermal Gravimetric Analysis, showing the weight loss of each CsPbBr3 NC sample between 100 and 550 C.

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