Oxalic Acid Enabled Emission Enhancement and Continuous Extraction of Chloride from Cesium Lead Chloride/Bromide Perovskite Nanocrystals

Wang, Shixun; Shen, Xinyu; Zhuang, Xingwei; Xue, Dingke; Zhang, Xiangtong; Zhu, Jinyang; Shi, Zhifeng; Kershaw, Stephen V.; Yu, William W.; Rogach, Andrey L.

doi:10.1002/smll.201901828

Cited by 27 publications

(26 citation statements)

References 26 publications

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“…[79,131,265] Therefore, additional postsynthetic ligand and additive passivation or heterostructure formation can be used to passivate some of the surface defects and boost the overall optical performances and/or NC stabilities. [93,94,[259][260][261][262][263][264][265][266][267][268]…”

Section: Ligands For Passivating Lhp Nc Surface Defectsmentioning

confidence: 99%

“…[274] Similarly, oxalic acid has been added to mixed halide LHP NC colloidal solutions, where it is able to chelate to the NC surface, not only to remove excess Pb 2+ or Cs + ions which cause surface defects, but to also control halide compositions through the stronger binding of oxalic acid to chloride in comparison to bromide. [267] Some ligands used in the direct synthesis of LHP NCs have been demonstrated to remove surface defects and boost PL QYs when added to the colloidal solution postsynthetically. For example, TOP was added to aged colloidal solutions of CsPbI 3 NCs to regain losses in PL QYs and prevent the transition to the nonperovskite phase (𝛿-phase) typically observed upon long-term storage.…”

Section: Intercalation Of Small Additives and Addition Of Excess Liga...mentioning

confidence: 99%

Section: Postsynthetic Ligand Modifications In Lhp Ncsmentioning

confidence: 99%

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Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

et al. 2021

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Lead halide perovskite (LHP) nanocrystals (NCs) have recently garnered enhanced development efforts from research disciplines owing to their superior optical and optoelectronic properties. These materials, however, are unlike conventional quantum dots, because they possess strong ionic character, labile ligand coverage, and overall stability issues. As a result, the system as a whole is highly dynamic and can be affected by slight changes of particle surface environment. Specifically, the surface ligand shell of LHP NCs has proven to play imperative roles throughout the lifetime of a LHP NC. Recent advances in engineering and understanding the roles of surface ligand shells from initial synthesis, through postsynthetic processing and device integration, finally to application performances of colloidal LHP NCs are covered here.

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Section: Ligands For Passivating Lhp Nc Surface Defectsmentioning

confidence: 99%

Section: Intercalation Of Small Additives and Addition Of Excess Liga...mentioning

confidence: 99%

Section: Postsynthetic Ligand Modifications In Lhp Ncsmentioning

confidence: 99%

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Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

et al. 2021

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“…The strong phonon mode at ≈70 cm −1 was assigned to the bending mode of Br-Pb-Br. [22][23][24] Compared to PeNCs-ODE, PeNCs-toluene exhibited a narrower phonon linewidth, illustrating better crystallinity [25] which was beneficial to the PL emission. To evaluate their optical performance, both PeNCs were diluted to an identical optical density (OD) value, meaning that they had the same concentration.…”

Section: Resultsmentioning

confidence: 99%

All‐Inorganic Perovskite Nanocrystals with Remarkably Enhanced Optoelectronic Properties Realized by an Alkene‐Free Solvent Strategy and Their Electroluminescence

Dou

Wang

et al. 2022

Advanced Optical Materials

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highly luminescent CsPbX 3 PeNCs are widely prepared through hot-injection methods using long-chain hydrocarbons oleic acid (OA) and oleylamine (OAm) as the surface capped ligands and octadecene (ODE) as the high-temperature reaction medium. [4][5][6] These long-chain hydrocarbons will significantly impact the optical and electrical properties of PeNCs, thereby determining the performance of perovskite LEDs (PeLEDs).The abundant organic ligands can effectively passivate the surface defects of PeNCs and provide colloidal stability in the solutions; however, they also form an insulating layer when transforming into solid films, which is deleterious to the injection of carriers into PeNCs emissive layers in PeLEDs. [7,8] Many efforts have been devoted to enhancing the carrier transport capabilities of PeNCs via resurfacing, ligand exchange, and/or surface ligand density control for improving the electroluminescence (EL) performance of the perovskite NCs based devices. [9][10][11] Zeng et al. regulated the antisolvent and optimized the purification cycles to control the ligand density, which realized 50-fold efficiency improvement. [10] Li and coworkers developed the combined method of metal salt treatment and short-chain ligand exchange to improve the carrier transport of PeNCs. [11] Sargent et al. recently achieved a bipolar shell to replace the OAm ligand for increasing the carrier mobility and reducing the trap density, which remarkably enhanced the external quantum efficiency (EQE) of PeLEDs to 22%. [9] Nonetheless, the effects of the dielectric alkene-based solvents on the optoelectric properties of PeNCs and thus, the performance of the PeLEDs is still unrevealed.Given the ionic nature of perovskites, ethyl acetate (EtOAc) with moderate polarity is usually adopted to purify PeNCs for maintaining their structural integrity and excellent optical properties. [12] However, the optoelectric properties of PeNCs will suffer from the residual ODE molecules, which lead to the formation of insulating barrier for injection and transport of carriers. Following the similarity solution principle, [13] it is difficult for the ODE molecules to be removed completely due to their incompatible with EtOAc, and they exist on the surface Hot-injection methods are widely used for the synthesis of colloidal perovskite nanocrystals (PeNCs). However, the long-chain hydrocarbon solvents with alkene groups, such as octadecene (ODE), cannot be removed completely due to the strong van der Waals force between ODE and surface ligands as well as the large difference in the polarity with ethyl acetate, which hinders the charge transport characteristic of PeNCs and thus reduces the performance of PeNC-based light-emitting diodes (PeLEDs). Herein, an alkene-free solvent-assisted strategy is reported to synthesize high-quality CsPbBr 3 PeNCs in toluene and it is found that the alkene-free solvent can significantly influence the morphology, composition, and optoelectronic properties of PeNCs. Compared to the traditional ODE solvent with alkene gro...

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“…By far, the PLQY of red-and green-emitting cesium lead halide perovskite has been enhanced to near unity [7,8], and consequently the external quantum efficiency (EQE) of perovskite NC LEDs has surpassed 20% [9][10][11][12], which can match the state-of-the-art performance of organic LEDs and quantum dot LEDs. Nevertheless, the performance of blue-emitting perovskite materials still falls behind their red and green counterparts, especially in the deep blue region with an emission wavelength of around 460 nm [13][14][15][16][17][18] or shorter, with a PLQY lower than 90%. Short-wavelength blue emission can be used to broaden the color gamut for display applications; therefore, it is valuable for the progress of display technology.…”

Section: Introductionmentioning

confidence: 99%

CsPb(Br/Cl)3 Perovskite Nanocrystals with Bright Blue Emission Synergistically Modified by Calcium Halide and Ammonium Ion

Zhang

Peng

et al. 2022

Nanomaterials

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Colloidal cesium lead halide (CsPbX3, X = Cl, Br, and I) perovskite nanocrystals (NCs) demonstrate supreme optical properties in the spectra region of infrared, red, and green. High-performance blue-emitting counterparts are still eagerly required for next-generation full-color displays. However, it is challenging to obtain efficient blue perovskite NCs, especially in a deep blue region with an emission wavelength of around 460 nm or shorter. Herein, calcium halide and ammonium ions are applied simultaneously to modify the CsPb(Br/Cl)3 NCs in situ to reduce surface defects, finally remarkably enhancing the photoluminescence quantum yield (PLQY) from 13% to 93% with an emission peak at 455 nm and the Commission Internationale de l’Eclairage (CIE) coordinates at (0.147, 0.030), which is close to the requirement of the Rec.2020 standard and also meets the requirement of blue emission in DCI-P3. Bright white emission and a wide color gamut are also achieved by combining the commercial red-emitting and green-emitting phosphors. The combination of time-resolved PL spectra and femtosecond transient absorption results discloses the reason for PLQY improvement as suppressing the nonradiative recombination.

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Oxalic Acid Enabled Emission Enhancement and Continuous Extraction of Chloride from Cesium Lead Chloride/Bromide Perovskite Nanocrystals

Abstract: Figure 4. a) FTIR spectra and b) Raman spectra (taken under excitation at 633 nm) of the pristine (black), the "2 s OxA" (red), and the "10 min OxA" (blue) CsPb(Cl/Br) 3 perovskite NCs.

Cited by 27 publications

References 26 publications

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

Recent Advances in Ligand Design and Engineering in Lead Halide Perovskite Nanocrystals

All‐Inorganic Perovskite Nanocrystals with Remarkably Enhanced Optoelectronic Properties Realized by an Alkene‐Free Solvent Strategy and Their Electroluminescence

CsPb(Br/Cl)3 Perovskite Nanocrystals with Bright Blue Emission Synergistically Modified by Calcium Halide and Ammonium Ion

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