Electronic Structure of CdSe Nanoparticles Adsorbed on Au Electrodes by an Organic Linker: Fermi Level Pinning of the HOMO

Markus, Tal Z.; Wu, Ming C.; Wang, L.; Waldeck, David H.; Oron, Dan; Naaman, Ron

doi:10.1021/jp9041167

Cited by 40 publications

(72 citation statements)

References 38 publications

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“…Such discrepancy could be explained by (i) impact of recombination [24], (ii) influence of specific adsorption of ions and dipoles of solvent [31], and (iii) non-negligible difference between E c and E Fn for CdSe QDs. Nevertheless, the obtained constancy in E v position regardless of the CdSe QD size is in a good agreement with the above-cited works [30][31][32][33][34][35][36].…”

Section: Photoelectrochemical Properties Of Cdse Films In Na 2 So 3 Solutionsupporting

confidence: 92%

“…Note that the obtained E c and E v values are anodically shifted by appr. 0.5 V in comparison with the values provided by theoretical calculations [30] and experimental findings (ultraviolet photoelectron emission spectroscopy [31][32][33], cyclic voltammetry in non-aqueous solutions [34][35][36]). Such discrepancy could be explained by (i) impact of recombination [24], (ii) influence of specific adsorption of ions and dipoles of solvent [31], and (iii) non-negligible difference between E c and E Fn for CdSe QDs.…”

Section: Photoelectrochemical Properties Of Cdse Films In Na 2 So 3 Solutionmentioning

confidence: 55%

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Size-dependent photocurrent switching in chemical bath deposited CdSe quantum dot films

Malashchonak

Streltsov

Mazanik

et al. 2016

J Solid State Electrochem

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Size-dependent photocurrent switching has been investigated in chemical bath deposited CdSe quantum dot (QD) films with band gaps 2.26, 2.09, and 1.81 eV (corresponds to nanoparticles' average diameter of 4, 5, and 10 nm). CdSe films generate only anodic photocurrent (exhibit n-type semiconductor behavior) in the solution which contains only acceptor of photoholes (SO 3 2− anions), whereas cathodic photocurrent (corresponding to p-type behavior) arises after immersion of the films in polyselenide electrolyte (containing Se n 2− /Se 2− redox system). Appearance of the cathodic photocurrent is related to chemisorptions of Se 2− and Se n 2− anions, as revealed by the cadmium underpotential deposition (UPD). Photocurrent switching from anodic to cathodic becomes more pronounced with decreasing of CdSe nanoparticle size because small quantum dots with their broadened band gaps have more favorable conduction band energy for electron injection to polyselenide anions. On the contrary, particle size does not play a significant role for the injection of photoholes into the electrolyte because the position of the valence band is weakly size-dependent, and anodic photocurrent is determined primarily by the real surface area of the electrode, which was found to be greater than the geometrical one by 1-2 orders of magnitude from cadmium UPD. Effective charge separation at the highly developed CdSe-electrolyte interface contributes to high incident photon-to-current conversion efficiency of photocurrent (IPCE~40 %).

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Section: Photoelectrochemical Properties Of Cdse Films In Na 2 So 3 Solutionsupporting

confidence: 92%

Section: Photoelectrochemical Properties Of Cdse Films In Na 2 So 3 Solutionmentioning

confidence: 55%

Size-dependent photocurrent switching in chemical bath deposited CdSe quantum dot films

Malashchonak

Streltsov

Mazanik

et al. 2016

J Solid State Electrochem

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“…103 Recently, Markus et al compared energy level positions for CdSe nanocrystals as measured by CV and by photoemission spectroscopy as a more sophisticated method. 109 Reasonable agreement was found, but as an interesting result the authors observed that the valence band became independent of the particle size due to a pinning effect when the nanoparticles were measured on an Au substrate. 109 This points out that interactions with a substrate may also influence the electrochemical measurements when studying thin films.…”

Section: Charge Separation In Polymer/nanoparticle Donor/acceptor Blendsmentioning

confidence: 96%

Elementary processes and limiting factors in hybrid polymer/nanoparticle solar cells

Borchert

2010

Energy Environ. Sci.

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Semiconductor nanoparticles are promising for use as electron acceptors in polymer-based bulk heterojunction solar cells. Potential advantages over fullerene derivates that are widely used in organic photovoltaics are tuneable absorption properties and the possibility to use elongated nanoparticles for more efficient electron transport. Despite these advantages, efficiencies obtained with hybrid polymer/ nanoparticle solar cells are still below those of state-of-the-art polymer/fullerene solar cells. This Perspective summarises the achievements in the field of hybrid solar cells, compares the knowledge on elementary processes in hybrid and organic systems and points out the most recent trends in research. The design of the polymer nanoparticle/interface by the choice of capping ligands and development of appropriate surface treatments for the nanoparticles plays an important role, and recent progress opens new perspectives for the future improvement of hybrid solar cells.

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“…Here, the HOMO energy is defined by the cutoff in the LEPET spectra, while the LUMO is defined by the peak in the TPPE spectra. 18 The HOMO-LUMO energy gaps obtained (6 nm). The difference LEPET spectra (below the Fermi level) that are obtained by subtracting the spectrum of the DT/Au, and TPPE spectra (above the Fermi level) of (c) CdSe (6 nm) and (d) CdSe (3.7 nm).…”

mentioning

confidence: 99%

“…It is expected that the size of the core will affect the properties of its wave function in a c/s NP. [18][19][20][21] To investigate the size effect we used small CdSe/ ZnS c/s NPs with an average diameter of 3.8 nm. Figure 5d shows the PL of these NPs on DT/Au and when DT molecules are adsorbed on the particles.…”

mentioning

confidence: 99%

How Isolated Are the Electronic States of the Core in Core/Shell Nanoparticles?

et al. 2011

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We investigated how isolated are the electronic states of the core in a core-shell (c/s) nanoparticles (NPs) from the surface, when the particles are self-assembled on Au substrates via a dithiol (DT) organic linker. Applying photoemission spectroscopy the electronic states of CdSe core only and CdSe/ZnS c/s NPs were compared. The results indicate that in the c/s NPs the HOMO interacts strongly with electronic states in the Au substrate and is pinned at the same energies, relative to the Fermi level, as the core only NPs. When the capping molecules of the NPs were replaced with thiolated molecules, an interaction between the thiol groups and the electronic states of the NPs was observed that depends on the properties of the NPs studied. Thiols binding to the NPs induce the formation of surface trap states. However, while for the core only CdSe NPs the LUMO states are strongly coupled to the surface traps, independent of their size, this coupling is size dependent in the case of the CdSe/ZnS c/s NPs. For a large core, the LUMO is decoupled from the surface trap states. When the core is small enough, the LUMO is delocalized and interacts with these states.

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Electronic Structure of CdSe Nanoparticles Adsorbed on Au Electrodes by an Organic Linker: Fermi Level Pinning of the HOMO

Cited by 40 publications

References 38 publications

Size-dependent photocurrent switching in chemical bath deposited CdSe quantum dot films

Size-dependent photocurrent switching in chemical bath deposited CdSe quantum dot films

Elementary processes and limiting factors in hybrid polymer/nanoparticle solar cells

How Isolated Are the Electronic States of the Core in Core/Shell Nanoparticles?

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