Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

Kroupa, Daniel M.; Vörös, Márton; Brawand, Nicholas P.; McNichols, Brett W.; Miller, Elisa M.; Gu, Jing; Nozik, Arthur J.; Sellinger, Alan; Galli, Giulia; Beard, Matthew C.

doi:10.1038/ncomms15257

Cited by 256 publications

(369 citation statements)

References 34 publications

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“…Therefore, most of the previously reported results related to BiVO 4 ‐based photoanodes13, 14, 16, 19, 47, 51, 52, 53 were measured in sulfite oxidation condition to show photo‐electrochemical properties of BiVO 4 ‐based electrodes independently of its poor water oxidation kinetics, as shown in Table S2 (Supporting Information). The photo‐electrochemical current densities of the BiVO 4 ‐based photoanodes4, 13, 14, 16, 17, 19, 20, 21, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 64, 65, 66, 67, 68, 69, 77 were plotted as a function of potential versus RHE. Thus, we measured PEC properties of BiVO 4 ‐based anodes under sulfite oxidation to figure out the effect of ligand engineering.…”

Section: Resultsmentioning

confidence: 99%

“…The shifts of the band edge energies of MnO can still be tuned over a wide range by controlling the intrinsic dipole moment of the ligand. Since the orientation and coverage of the ligands on the surface, and the contribution of the effective dipole moment are weakly coupled, we can predict the change in the energy shift from the controlled change in the intrinsic dipole moment of the ligand 50, 51, 52, 53, 54…”

Section: Resultsmentioning

confidence: 99%

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Efficient Water Splitting Cascade Photoanodes with Ligand‐Engineered MnO Cocatalysts

et al. 2018

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The band edge positions of semiconductors determine functionality in solar water splitting. While ligand exchange is known to enable modification of the band structure, its crucial role in water splitting efficiency is not yet fully understood. Here, ligand‐engineered manganese oxide cocatalyst nanoparticles (MnO NPs) on bismuth vanadate (BiVO4) anodes are first demonstrated, and a remarkably enhanced photocurrent density of 6.25 mA cm−2 is achieved. It is close to 85% of the theoretical photocurrent density (≈7.5 mA cm−2) of BiVO4. Improved photoactivity is closely related to the substantial shifts in band edge energies that originate from both the induced dipole at the ligand/MnO interface and the intrinsic dipole of the ligand. Combined spectroscopic analysis and electrochemical study reveal the clear relationship between the surface modification and the band edge positions for water oxidation. The proposed concept has considerable potential to explore new, efficient solar water splitting systems.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Efficient Water Splitting Cascade Photoanodes with Ligand‐Engineered MnO Cocatalysts

et al. 2018

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“…

absorption spectrum, low-cost, solutionprocessable fabrication, and compatibility with flexible substrates. [12][13][14] For the QDs in solar cell applications, the multiple excitation generation in QDs gives the possibility to overcome the Shockley-Queisser theoretical limitation on the power conversion efficiency (PCE) of a single-junction solar cell since the QD may produce more than one electron-hole pair after absorbed one high-energy photon. [12][13][14] For the QDs in solar cell applications, the multiple excitation generation in QDs gives the possibility to overcome the Shockley-Queisser theoretical limitation on the power conversion efficiency (PCE) of a single-junction solar cell since the QD may produce more than one electron-hole pair after absorbed one high-energy photon.

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mentioning

confidence: 99%

Highly Stabilized Quantum Dot Ink for Efficient Infrared Light Absorbing Solar Cells

Jia

Chen

Zheng

et al. 2019

Advanced Energy Materials

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absorption spectrum, low-cost, solutionprocessable fabrication, and compatibility with flexible substrates. [8][9][10][11] Furthermore, the surface ligand exchange of postsynthetic QDs allows for tailoring QD surface chemistry, which provides large freedom to fine-tune the optoelectronic properties of QDs, therefore engineering the device performance. [12][13][14] For the QDs in solar cell applications, the multiple excitation generation in QDs gives the possibility to overcome the Shockley-Queisser theoretical limitation on the power conversion efficiency (PCE) of a single-junction solar cell since the QD may produce more than one electron-hole pair after absorbed one high-energy photon. [15,16] Over the past few years, benefiting from the fundamental studies in controlling QD surface chemistry, device architecture, interfacial properties and electro-optics within the QD solar cell (QDSC) devices, significant progress was obtained and a PCE of more than 12% was achieved for the PbS QDSC. [14,17] Meanwhile, the QDSC has good stability both under continuous illumination and long-term storage under ambient conditions, showing great potential for the development of highly efficient and stable photovoltaic devices. [18,19] During the QD synthesis, the long native organic ligand (such as oleic acid (OA)) is generally applied to cover the QD surface to control the dot size and make the colloidal system stable in organic solvents. [20,21] However, when the QDs is used to construct a solar cell, such long organic ligands should be replaced by small surface binding species to decrease the distance between dots and meanwhile minimize QD surface traps, facilitating charge-transport within the QD solid. Insufficient ligand exchange will lead to oxidation on the QD surface, which affects the photovoltaic performance and stability of QDSCs. [22][23][24] Liquid-state ligand exchange approach provides an efficient way to replace the long organic ligand on the QD surface with small binding species, such as small organic molecules or lead halide (PbX 2 , X = Br or I). [2,25,26] The ligand-exchanged QDs are dispersed in a polar butylamine solvent forming a concentrated QD ink, which can be used for the deposition of a thick QD solid film with a single-step deposition technique, significantly decreasing the time for QD solid film deposition and improving material usage efficiency. [17,25] The QD solid film prepared with the QD ink shows better characteristics compared with that Liquid-state ligand exchange provides an efficient approach to passivate a quantum dot (QD) surface with small binding species and achieve a QD ink toward scalable QD solar cell (QDSC) production. Herein, experimental studies and theoretical simulations are combined to establish the physical principles of QD surface properties induced charge carrier recombination and collection in QDSCs. Ammonium iodide (AI) is used to thoroughly replace the native oleic acid ligand on the PbS QD surface forming a concentrated QD ink, which has high stability of more than 30 ...

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“…However, Pt-or Au-loaded TiO 2 showed a negative shift of overpotential for HER, implying that the exposed metal sites are the active sites instead of the adsorbed ligands, and the surface functionalities modulate the accumulated charge carrier densities on the metal sites [68,71]. Furthermore, the surface dipole at the solid-liquid interface can be modulated by the intrinsic dipole moments, the geometrics and orientation of ligands functionalized on material, and the interaction between adjacent molecules in different nanomaterials can enhance the band edge modulation over 2.0 eV [72,73].…”

Section: Surface Functionalization At the Solid-liquid Interface Formentioning

confidence: 99%

Understanding Surface Modulation to Improve the Photo/Electrocatalysts for Water Oxidation/Reduction

Cho

Lee

2020

Molecules

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Water oxidation and reduction reactions play vital roles in highly efficient hydrogen production conducted by an electrolyzer, in which the enhanced efficiency of the system is apparently accompanied by the development of active electrocatalysts. Solar energy, a sustainable and clean energy source, can supply the kinetic energy to increase the rates of catalytic reactions. In this regard, understanding of the underlying fundamental mechanisms of the photo/electrochemical process is critical for future development. Combining light-absorbing materials with catalysts has become essential to maximizing the efficiency of hydrogen production. To fabricate an efficient absorber-catalysts system, it is imperative to fully understand the vital role of surface/interface modulation for enhanced charge transfer/separation and catalytic activity for a specific reaction. The electronic and chemical structures at the interface are directly correlated to charge carrier movements and subsequent chemical adsorption and reaction of the reactants. Therefore, rational surface modulation can indeed enhance the catalytic efficiency by preventing charge recombination and prompting transfer, increasing the reactant concentration, and ultimately boosting the catalytic reaction. Herein, the authors review recent progress on the surface modification of nanomaterials as photo/electrochemical catalysts for water reduction and oxidation, considering two successive photogenerated charge transfer/separation and catalytic chemical reactions. It is expected that this review paper will be helpful for the future development of photo/electrocatalysts.

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Tuning colloidal quantum dot band edge positions through solution-phase surface chemistry modification

Cited by 256 publications

References 34 publications

Efficient Water Splitting Cascade Photoanodes with Ligand‐Engineered MnO Cocatalysts

Efficient Water Splitting Cascade Photoanodes with Ligand‐Engineered MnO Cocatalysts

Highly Stabilized Quantum Dot Ink for Efficient Infrared Light Absorbing Solar Cells

Understanding Surface Modulation to Improve the Photo/Electrocatalysts for Water Oxidation/Reduction

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