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

Brown, Alasdair A. M.; Hooper, Thomas J. N.; Veldhuis, Sjoerd A.; Chin, Xin Yu; Bruno, Annalisa; Vashishtha, Parth; Tey, Ju Nie; Jiang, Liudi; Bahulayan, D.; Pu, Suan Hui; Mhaisalkar, Subodh; Mathews, Nripan

doi:10.1039/c9nr02566a

Cited by 73 publications

(84 citation statements)

References 37 publications

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“…9.5 ppm and 11 ppm that should correspond to acid protons. 44 The narrowing of the 31 P peak at 26 ppm could arise because a singly deprotonated phosphonic acid may coordinate to the surface in a monodentate fashion, permitting rotation that could help to average inhomogeneous broadening. The presence of two acid 1 H NMR signals suggest that there are distinct binding sites on the surface for the monoanionic 10-undecenylphosphonate.…”

Section: Resultsmentioning

confidence: 99%

Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

et al. 2020

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Cesium lead halide perovskite quantum dots (QDs) have gained significant attention as next-generation optoelectronic materials; however, their properties are highly dependent on their surface chemistry. The surfaces of cuboidal CsPbBr3 QDs have been intensively studied by both theoretical and experimental techniques, but fundamental questions still remain about the atomic termination of the QDs. The binding sites and modes of ligands at the surface remain unproven. Herein, we demonstrate that solid-state NMR spectroscopy allows the unambiguous assignments of organic surface ligands via 1H, 13C, and 31P NMR. Surface-selective 133Cs solid-state NMR spectra show the presence of an additional 133Cs NMR signal with a unique chemical shift that is attributed to Cs atoms terminating the surface of the particle and which are likely coordinated by carboxylate ligands. Dipolar dephasing curves that report on the distance between the surface ammonium ligands and Cs and Pb were recorded using double resonance 1H{133Cs} and 1H{207Pb} RESPDOR experiments. Model QD surface slabs with different possible surface terminations were generated from the CsPbBr3 crystal structure and theoretical RESPDOR dipolar dephasing curves considering all possible 1H-133Cs/207Pb spin pairs were then calculated. Comparison of the calculated and experimental RESPDOR curves indicates the particles are CsBr terminated (not PbBr2 terminated), with alkylammonium ligands situated within surface Cs vacancies, consistent with the surface-selective 133Cs NMR experiments. These results highlight the utility of high-resolution solid-state NMR spectroscopy for studying ligand binding and the surface structure of nanomaterials.

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Section: Resultsmentioning

confidence: 99%

Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

et al. 2020

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“…Typically, short esters have been most successful. Depending on the ligand system employed, butyl acetate, [44] ethyl acetate, [35,41,43,[71][72][73][74][75][76][77] mixtures of ethyl and methyl acetate, [78,79] and methyl acetate alone, [67,[80][81][82][83] have been employed. Figure 6 shows a screening study of 36 potential antisolvents, it concurred on the efficacy of short esters, but indicated that diethylene glycol dimethyl ether (diglyme) was the most effective.…”

Section: Antisolvent Purificationmentioning

confidence: 99%

“…[80] This remarkable stability toward antisolvent washing was later attributed to the interligand hydrogen bonding between adjacent octylphosphonate ligands. [73] Figure 5. "Triple-ligand" surface passivation approach for CsPbBr 3 nanocrystals: a) The precursors and synthesis protocol, b) TEM image, c) HRTEM image, d) the three ligands employed, TOAB acts only as a solvation agent while DDAB and OTAc coordinate to the NC surface, e) photograph of the purified NC ink, f) time-resolved photoluminescence data, and g) current density against voltage plot for LEDs fabricated from NCs with either oleic acid or octanoic acid ligands.…”

Section: Antisolvent Purificationmentioning

confidence: 99%

“…The presence of two hydroxyl and one phosphonyl group on the same binding head allows phosphonic acids to bind to a surface with an anionic group (i.e., PO−) while retaining the capacity to form two hydrogen bonds (see Figure 11b for diagram). [73] This is a unique property of phosphonic acids, which enables the formation of interligand hydrogen bonds to enhance NC binding. However, similar surface chemistry could be envisaged for sulfonic acid groups binding to a surface as a Lewis base through a sulfonyl group.…”

Section: Phosphonic Acidsmentioning

confidence: 99%

“…[76] Copyright 2019, American Chemical Society), and b) the proposed interligand hydrogen bonding motif formed between adjacent octylphosphonate species on the NC surface (adapted with permission. [73] Copyright 2019, Royal Society of Chemistry).…”

Section: Zwitterionic Ligandsmentioning

confidence: 99%

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Lead Halide Perovskite Nanocrystals: Room Temperature Syntheses toward Commercial Viability

Brown

Bahulayan

Jiang

et al. 2020

Advanced Energy Materials

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In this progress report, recent improvements to the room temperaturesyntheses of lead halide perovskite nanocrystals (APbX3, X = Cl, Br, I) are assessed, focusing on various aspects which influence the commercial viability of the technology. Perovskite nanocrystals can be prepared easily from low‐cost precursors under ambient conditions, yet they have displayed near‐unity photoluminescence quantum yield with narrow, highly tunable emission peaks. In addition to their impressive ambipolar charge carrier mobilities, these properties make lead halide perovskite nanocrystals very attractive for light‐emitting diode (LED) applications. However, there are still many practical hurdles preventing commercialization. Recent developments in room temperature synthesis and purification protocols are reviewed, closely evaluating the suitability of particular techniques for industry. This is followed by an assessment of the wide range of ligands deployed on perovskite nanocrystal surfaces, analyzing their impact on colloidal stability, as well as LED efficiency. Based on these observations, a perspective on important future research directions that can expedite the industrial adoption of perovskite nanocrystals is provided.

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Surface Chemistry Engineering of Perovskite Quantum Dots: Strategies, Applications, and Perspectives

et al. 2021

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The presence of surface ligands not only plays a key role in keeping the colloidal integrity and non‐defective surface of metal halide perovskite quantum dots (PQDs), but also serves as a knob to tune their optoelectronic properties for a variety of exciting applications including solar cells and light‐emitting diodes. However, these indispensable surface ligands may also deteriorate the stability and key properties of PQDs due to their highly dynamic binding and insulating nature. To address these issues, a number of innovative surface chemistry engineering approaches have been developed in the past few years. Based on an in‐depth fundamental understanding of the surface atomistic structure and surface defect formation mechanism in the tiny nanoparticles, a critical overview focusing on the surface chemistry engineering of PQDs including advanced colloidal synthesis, in‐situ surface passivation, and solution‐phase/solid‐state ligand exchange is presented, after which their unprecedented achievements in photovoltaics and other optoelectronics are presented. The practical hurdles and future directions are critically discussed to inspire more rational design of PQD surface chemistry toward practical applications.

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

Abstract: Ligand exchange with octylphosphonate enhances PLQY and LED efficiency.

Cited by 73 publications

References 37 publications

Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Lead Halide Perovskite Nanocrystals: Room Temperature Syntheses toward Commercial Viability

Surface Chemistry Engineering of Perovskite Quantum Dots: Strategies, Applications, and Perspectives

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

Abstract: Ligand exchange with octylphosphonate enhances PLQY and LED efficiency.

Cited by 73 publications

References 37 publications

Surface Termination of CsPbBr3 Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Surface Termination of CsPbBr3 Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Lead Halide Perovskite Nanocrystals: Room Temperature Syntheses toward Commercial Viability

Surface Chemistry Engineering of Perovskite Quantum Dots: Strategies, Applications, and Perspectives

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Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy

Surface Termination of CsPbBr₃ Perovskite Quantum Dots Determined by Solid-State NMR Spectroscopy