Stoichiometric Control of Lead Chalcogenide Nanocrystal Solids to Enhance Their Electronic and Optoelectronic Device Performance

Oh, Soong Ju; Berry, Nathaniel E.; Choi, Jung Chan; Gaulding, E. Ashley; Paik, Taejong; Hong, Sung Hoon; Murray, Christopher B.; Kagan, Cherie R.

doi:10.1021/nn3057356

Cited by 215 publications

(331 citation statements)

References 49 publications

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“…Another postsynthesis approach of electronic modification is stoichiometry control via deposition of excess lead or chalcogen. 42,43 Although neutral atomic vacancies are unlikely to form during solution synthesis (as discussed before), this postsynthesis control can produce QDs with excess Pb or S (i.e., QD with neutral S or Pb vacancies). According to previous calculations 8,16 and our own DFT results (not shown here), neutral Pb vacancies produce IGS near the valence band, while neutral S or L (ligand) vacancies produce IGS near the conduction band.…”

Section: Spectroscopic Evidence and Further Theoretical Support On Thmentioning

confidence: 99%

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Molecular Oxygen Induced in-Gap States in PbS Quantum Dots

Zhang

Zherebetskyy

Bronstein³

et al. 2015

ACS Nano

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Artificial solids composed of semiconductor quantum dots (QDs) are being developed for large-area electronic and optoelectronic applications, but these materials often have defect-induced in-gap states (IGS) of unknown chemical origin.Here we performed scanning probe based spectroscopic analysis and density functional theory calculations to determine the nature of such states and their electronic structure. We found that IGS near the valence band occur frequently in the QDs except when treated with reducing agents. Calculations on various possible defects and chemical spectroscopy revealed that molecular oxygen is most likely at the origin of these IGS. We expect this impurity-induced deep IGS to be a common occurrence in ionic semiconductors, where the intrinsic vacancy defects either do not produce IGS or produce shallow states near band edges. Ionic QDs with surface passivation to block impurity adsorption are thus ideal for highefficiency optoelectronic device applications.

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Section: Spectroscopic Evidence and Further Theoretical Support On Thmentioning

confidence: 99%

“…exhibit unintentional p-type doping even in inert atmosphere, with carrier densities of 10 16 À10 17 cm À3 for QDs of 5À6 nm diameter. 42 …”

Section: Spectroscopic Evidence and Further Theoretical Support On Thmentioning

confidence: 99%

Molecular Oxygen Induced in-Gap States in PbS Quantum Dots

Zhang

Zherebetskyy

Bronstein³

et al. 2015

ACS Nano

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“…This may happen via engineering of the composition, by doping or the formation of heterostructures. 19,[38][39][40][41][42] Colloidal oligomeric hybrid nanoparticles (HNPs) offer the possibility to tailor material combinations for advanced applications in the fields of photocatalysis and (opto-)electronics. 43,44 A number of studies have demonstrated the excellent photo-catalytic properties of metal-semiconductor HNPs in liquid solution, which are based on an efficient separation of photogenerated charge carriers.…”

mentioning

confidence: 99%

Metal Domain Size Dependent Electrical Transport in Pt-CdSe Hybrid Nanoparticle Monolayers

Meyns¹,

Willing²,

Lehmann³

et al. 2015

ACS Nano

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Thin films prepared of semiconductor nanoparticles are promising for low-cost electronic applications such as transistors and solar cells. One hurdle for their breakthrough is their notoriously low conductivity. To address this, we precisely decorate CdSe nanoparticles with platinum domains of one to three nanometers in diameter by a facile and robust seeded growth method. We demonstrate the transition from semiconductor to metal dominated conduction in monolayered films. By adjusting the platinum content in such solutionprocessable hybrid, oligomeric nanoparticles the dark currents through deposited arrays become tunable while maintaining electronic confinement and photoconductivity.Comprehensive electrical measurements allow determining the reigning charge transport mechanisms.Keywords: Colloidal hybrid nanoparticles, electrical transport, photoconductivity, size effects, Langmuir-Blodgett deposition 2 Continuous progress in the control of nanoparticle (NP) size, composition, and shape has led to unprecedented possibilities in material design targeting applications as diverse as medical therapy and diagnostics and solid state devices. 1 Nanoparticle thin-film devices are studied and applied in various contexts, especially with regard to their optoelectronic and electronic properties. 2 The solution processability of nanoparticle building blocks makes them particularly attractive for applications such as photovoltaics, 3-6 light emitting diodes, 7-9 as well as chemical sensing and photodetection. [10][11][12][13][14] The fundamental electrical properties of single material systems consisting of either semiconductor or metal nanoparticles have been studied especially with respect to quantum-mechanical coupling phenomena, [15][16][17][18][19][20] Coulombblockade behavior, 21,22 transistor characteristics, [23][24][25] and photo conductivity. 20,26,27 Nanoparticles prepared by colloidal chemistry can be arranged into ordered arrays by a variety of methods. Among them are the widely applied spin-coating, self-assembly, 28,29 and the Langmuir-Blodgett technique. 30 In particular, the latter relies on a stabilizing layer of organic surfactants that enables the dispersion and assembly of nanoparticles on a liquid sub-phase. While highly ordered films can be achieved, a big drawback of this method is the creation of spatial and energetic barriers between adjacent nanoparticles by the organic stabilizers. This usually leads to a high resistivity of the arrays. 31 (CZTS) and Au were recently reported to improve the photoresponse and -stability compared to pure CZTS multi-layered photodetectors. 51 Increasing the current in a semiconductor nanoparticle array by deposition of metallic domains seems intuitive. Anyhow, it is less clear how the metal domain size and thus the degree of coupling between the domains influences the dark and especially the photocurrents. In the following, we report on the synthesis of well-defined oligomeric Pt-CdSe HNPs by a simple seeded-growth approach and the effect of Pt domain size ...

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“…As the wavefunctions of charge carriers are spatially confined in a smaller volume than in the parental bulk material [49], it follows that the probability of finding charge carriers at the particle surface is greatly increased. The consequence of both effects is that, in QDs, a significant proportion of generated charge carriers will get trapped at surface sites that are energetically removed from the semiconductor's charge transport level [72]. This effect is exacerbated for MEG devices due to the requirement for strong confinement [73,74].…”

Section: Impacts Of the Qd Surface On Meg In A Device Environmentmentioning

confidence: 99%

Multiple exciton generation in quantum dot-based solar cells

et al. 2017

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Multiple exciton generation (MEG) in quantumconfined semiconductors is the process by which multiple bound charge-carrier pairs are generated after absorption of a single high-energy photon. Such charge-carrier multiplication effects have been highlighted as particularly beneficial for solar cells where they have the potential to increase the photocurrent significantly. Indeed, recent research efforts have proved that more than one chargecarrier pair per incident solar photon can be extracted in photovoltaic devices incorporating quantum-confined semiconductors. While these proof-of-concept applications underline the potential of MEG in solar cells, the impact of the carrier multiplication effect on the device performance remains rather low. This review covers recent advancements in the understanding and application of MEG as a photocurrent-enhancing mechanism in quantum dot-based photovoltaics.

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Stoichiometric Control of Lead Chalcogenide Nanocrystal Solids to Enhance Their Electronic and Optoelectronic Device Performance

Cited by 215 publications

References 49 publications

Molecular Oxygen Induced in-Gap States in PbS Quantum Dots

Molecular Oxygen Induced in-Gap States in PbS Quantum Dots

Metal Domain Size Dependent Electrical Transport in Pt-CdSe Hybrid Nanoparticle Monolayers

Multiple exciton generation in quantum dot-based solar cells

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