Ultrabright PbSe Magic-sized Clusters

Evans, Christopher M.; Guo, Li; Peterson, Jeffrey J.; Maccagnano-Zacher, Sara; Krauss, Todd D.

doi:10.1021/nl801685a

Cited by 153 publications

(204 citation statements)

References 28 publications

(46 reference statements)

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“…For nanocrystals smaller than 3 nm (1.0-1.3 eV), the procedure is based on a two fold scale up of a procedure reported previously 58 . Briefly, lead (II) oxide (16 mmol; 3.56 g) and oleic acid (64 mmol; 20 ml) were dissolved in ODE (10-20 ml, depending on desired nanocrystal size).…”

Section: Methodsmentioning

confidence: 99%

In situ measurement of exciton energy in hybrid singlet-fission solar cells

et al. 2012

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singlet exciton fission-sensitized solar cells have the potential to exceed the shockley-Queisser limit by generating additional photocurrent from high-energy photons. Pentacene is an organic semiconductor that undergoes efficient singlet fission-the conversion of singlet excitons into pairs of triplets. However, the pentacene triplet is non-emissive, and uncertainty regarding its energy has hindered device design. Here we present an in situ measurement of the pentacene triplet energy by fabricating a series of bilayer solar cells with infrared-absorbing nanocrystals of varying bandgaps. We show that the pentacene triplet energy is at least 0.85 eV and at most 1.00 eV in operating devices. our devices generate photocurrent from triplets, and achieve external quantum efficiencies up to 80%, and power conversion efficiencies of 4.7%. This establishes the general use of nanocrystal size series to measure the energy of non-emissive excited states, and suggests that fission-sensitized solar cells are a favourable candidate for third-generation photovoltaics.

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Section: Methodsmentioning

confidence: 99%

In situ measurement of exciton energy in hybrid singlet-fission solar cells

et al. 2012

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“…In this context, ultrasmall nanocrystals have the ability to (1) serve as active precursors in the formation of various anisotropic nanostructures, 15,[19][20][21] and (2) undergo fast charge separation and slow recombination. [22][23][24] Despite immense interest in ultrasmall nanocrystals in fundamental chemical processes, only a handful of high temperature [25][26][27] or alkylphosphine [28][29] precursor-based synthetic methods have been developed to prepare them. Very recently, low temperature, nonphosphinated methods for synthesis of ultrasmall CdSe nanocrystals were reported.…”

Section: Introductionmentioning

confidence: 99%

Mechanistic Study of the Formation of Bright White Light-Emitting Ultrasmall CdSe Nanocrystals: Role of Phosphine Free Selenium Precursors

Dolai¹,

Dutta

Muhoberac³

et al. 2015

Chem. Mater.

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ABSTRACT:We have designed a new non-phosphinated reaction pathway, which includes synthesis of a new, highly reactive Se-bridged organic species (chalcogenide precursor), to produce bright white light-emitting ultrasmall CdSe nanocrystals of high quality under mild reaction conditions. The detailed characterization of structural properties of the selenium precursor through combined 77 Se NMR and laser desorption ionization-mass spectrometry (LDI-MS) provided valuable insights into Se release and delineated the nanocrystal formation mechanism at the molecular level. The 1 H NMR study showed that the rate of disappearance of Se-precursor maintained a single-exponential decay with a rate constant of 2.3 x 10 -4 s -1 at room temperature. Furthermore, the combination of LDI-MS and optical spectroscopy was used for the first time to deconvolute the formation mechanism of our bright white light-emitting nanocrystals, which demonstrated initial formation of a smaller key nanocrystal intermediate (CdSe)19. Application of thermal driving force for destabilization resulted in (CdSe)n nanocrystal generation with n = 29-36 through continuous dissolution and addition of monomer onto existing nanocrystals while maintaining a living-polymerization type growth mode. Importantly, our ultrasmall CdSe nanocrystals displayed an unprecedentedly large fluorescence quantum yield of ~27% for this size regime (<2.0 nm diameter). These mixed oleylamine and cadmium benzoate ligand-coated CdSe nanocrystals showed a fluorescence lifetime of ~90 ns, a significantly large value for such small nanocrystals, which was due to delocalization of the exciton wavefunction into the ligand monolayer. We believe our findings will be relevant to formation of other metal chalcogenide nanocrystals through expansion of the understanding and manipulation of surface ligand chemistry, which together will allow the preparation of "artificial solids" with high charge conductivity and mobility for advanced solid-state device applications.3

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“…2 Accordingly, colloidal PbSe QDs can be engineered to absorb and emit in a vast spectral range, spanning from ∼800 to 4000 nm with high photoluminescence (PL) emission quantum yields (QYs). [3][4][5][6][7][8] Hence, PbSe QDs are important materials for near-IR (NIR; >700 nm) and mid-IR (>2500 nm) applications, including biological imaging/labeling, 9,10 solar cells, [11][12][13][14][15][16] light-emitting devices, 17 and telecommunications. 18,19 PbSe nanocrystals (NCs) are especially attractive in the PV application, with a multiple exciton generation effect reported.…”

Section: ' Introductionmentioning

confidence: 99%

Low-Temperature Approach to High-Yield and Reproducible Syntheses of High-Quality Small-Sized PbSe Colloidal Nanocrystals for Photovoltaic Applications

Ouyang¹,

Schuurmans²,

Zhang³

et al. 2011

ACS Appl. Mater. Interfaces

106

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Small-sized PbSe nanocrystals (NCs) were syn-thesized at low temperature such as 50−80 °C with high reaction yield (up to 100%), high quality, and high synthetic reproducibility, via a noninjection-based one-pot approach. These small-sized PbSe NCs with their first excitonic absorption in wavelength shorter than 1200 nm (corresponding to size < ∼3.7 nm) were developed for photovoltaic applications requiring a large quantity of materials. These colloidal PbSe NCs, also called quantum dots, are high-quality, in terms of narrow size distribution with a typical standard deviation of ∼7−9%, excellent optical properties with high quantum yield of ∼50−90% and small full width at half-maximum of ∼130−150 nm of their band-gap photoemission peaks, and high storage stability. Our synthetic design aimed at promotion of the formation of PbSe monomers for fast and sizable nucleation with the presence of a large number of nuclei at low temperature. For formation of the PbSe monomer, our low-temperature approach suggests the existence of two pathways of Pb−Se (route a) and Pb−P (route b) complexes. Either pathway may dominate, depending on the method used and its experimental conditions. Experimentally, a reducing/nucleation agent, diphenylphosphine, was added to enhance route b. The present study addresses two challenging issues in the NC community, the monomer formation mechanism and the reproducible syntheses of small-sized NCs with high yield and high quality and large-scale capability, bringing insight to the fundamental understanding of optimization of the NC yield and quality via control of the precursor complex reactivity and thus nucleation/growth. Such advances in colloidal science should, in turn, promote the development of next-generation low-cost and high-efficiency solar cells. Schottky-type solar cells using our PbSe NCs as the active material have achieved the highest power conversion efficiency of 2.82%, in comparison with the same type of solar cells using other PbSe NCs, under Air Mass 1.5 global (AM 1.5G) irradiation of 100 mW/cm2.

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Ultrabright PbSe Magic-sized Clusters

Cited by 153 publications

References 28 publications

In situ measurement of exciton energy in hybrid singlet-fission solar cells

In situ measurement of exciton energy in hybrid singlet-fission solar cells

Mechanistic Study of the Formation of Bright White Light-Emitting Ultrasmall CdSe Nanocrystals: Role of Phosphine Free Selenium Precursors

Low-Temperature Approach to High-Yield and Reproducible Syntheses of High-Quality Small-Sized PbSe Colloidal Nanocrystals for Photovoltaic Applications

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