Size and Bandgap Control in the Solution-Phase Synthesis of Near-Infrared-Emitting Germanium Nanocrystals

Ruddy, Daniel A.; Johnson, Justin C.; Smith, Eric R.; Neale, Nathan R.

doi:10.1021/nn102728u

Cited by 139 publications

(269 citation statements)

References 51 publications

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“…Colloidal quantum dots (CQDs) are promising candidates for next-generation photovoltaics owing to their unique properties such as high absorption coefficient, tunable band gap, and multiple exciton generation effect. [1][2][3][4] The solutionbased process also has provided high feasibility of realizing flexible and large scale photovoltaic devices with costeffective fabrication. [5][6][7][8] Despite these favorable characteristics, poor charge transport and imperfect surface status of CQDs hinder high photovoltaic performance compared to the theoretical conversion efficiency.…”

mentioning

confidence: 99%

Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

Kim

Hong

Hou

et al. 2016

Applied Physics Letters

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We investigate time-dependent inorganic ligand exchanging effect and photovoltaic performance of lead sulfide (PbS) nanocrystal films. With optimal processing time, volume shrinkage induced by residual oleic acid of the PbS colloidal quantum dot (CQD) was minimized and a crack-free film was obtained with improved flatness. Furthermore, sufficient surface passivation significantly increased the packing density by replacing from long oleic acid to a short iodide molecule. It thus facilities exciton dissociation via enhanced charge carrier transport in PbS CQD films, resulting in the improved power conversion efficiency from 3.39% to 6.62%. We also found that excess iodine ions on the PbS surface rather hinder high photovoltaic performance of the CQD solar cell.

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mentioning

confidence: 99%

Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

Kim

Hong

Hou

et al. 2016

Applied Physics Letters

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“…Bottom-up solution-phase synthetic chemistry methods offer better control of the size and shape of the nanoparticles, but often do not provide the good crystallinity required for many applications, and require the use of longchain ligands and surfactants to stabilize the particle surface and control growth. [10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26] Due to their ease of preparation, these solution-phase methods are also more accessible to many researchers and more amenable to scaling. As a result, their development is in great demand to prepare high-quality materials for detailed chemistry and physical studies, essential for their eventual integration into practical devices.…”

Section: Synthesis Of Nanoamorphous Germanium and Itsmentioning

confidence: 99%

“…[8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24] The germanium sources in these investigations are usually the germanium halides, GeX n , or organogermanes [23,24] in which the Ge center is either in the 4 + or 2 + oxidation state (e.g., GeCl 4 , GeBr 4 , GeI 2 ), and long-chain phosphines and alkenes are often used as surface protection ligands for nanoparticle stabilization. The reducing agents used in these investigations are usually the strong ones, such as LiAlH 4 , NaBH 4 , sodium, sodium naphthalide, butyllithium, and Ge Zintl salts.…”

Section: Synthesis Of Nanoamorphous Germanium and Itsmentioning

confidence: 99%

Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium

Dag

Henderson

Ozin

2012

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A simple reaction between a mild reducing agent such as a trialkoxysilane and GeIV species such as germanium tetraalkoxides in a room‐temperature water/alcohol solution produces silica‐coated ultrasmall (2–3 nm) amorphous germanium nanoparticles (na‐Ge/SiO2). The initial reaction involves the straightforward hydrolysis and condensation of the precursors, Ge(OCH2CH3)4 and (CH3CH2O)3SiH, where the reaction rate depends on the water concentration in the reaction medium. These processes can be further accelerated by adding acid to the reaction medium or carrying out the reaction at higher temperatures. At low water contents (up to 50% water/ethanol) and low acid concentrations, the reaction proceeds as a clear solution, and no precipitation is observed. The initially colorless clear solution progressively changes to pale yellow, yellow, orange, red, and finally dark red as the na‐Ge particles grow. Evaporation of the solvent yields a reddish‐brown powder/monolith consisting of na‐Ge, embedded in an encapsulating amorphous silica matrix, na‐Ge/SiO2. The formation of na‐Ge proceeds extremely slowly and follows a first‐order dependence on both water concentration and diameter of the na‐Ge particles under the reaction conditions used. Annealing of the na‐Ge/SiO2 powder under an inert atmosphere at 600 °C produces ultrasmall germanium nanocrystals (nc‐Ge) embedded in amorphous silica (nc‐Ge/SiO2). Freestanding, colloidally stable nc‐Ge is obtained by chemical etching of the encapsulating silica matrix.

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“…[1][2][3][4][5][6] It is remarkable that quantum confinement has enabled efficient light emission from both Si and Ge NCs, [7][8][9][10][11] leading to great promise for optoelectronic integration. The light emission from Si and Ge NCs is usually inherently dependent on the NC-size-induced quantum confinement effect.…”

Section: Introductionmentioning

confidence: 99%

Twinned silicon and germanium nanocrystals: Formation, stability and quantum confinement

et al. 2015

AIP Advances

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Although twins are often observed in Si/Ge nanocrystals (NCs), little theoretical investigation has been carried out to understand this type of important planar defects in Si/Ge NCs. We now study the twinning of Si/Ge NCs in the frame work of density functional theory by representatively considering single-twinned and fivefold-twinned Si/Ge NCs. It is found that the formation of twinned Si/Ge NCs is thermodynamically possible. The effect of twinning on the formation of Si NCs is different from that of Ge NCs. For both Si and Ge NCs twinning enhances their stability. The quantum confinement effect is weakened by twinning for Si NCs. Twinning actually enhances the quantum confinement of Ge NCs when they are small (<136 atoms), while weakening the quantum confinement of Ge NCs as their size is large (>136 atoms). The current results help to better understand the experimental work on twinned Si/Ge NCs and guide the tuning of Si/Ge-NC structures for desired properties.

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Size and Bandgap Control in the Solution-Phase Synthesis of Near-Infrared-Emitting Germanium Nanocrystals

Cited by 139 publications

References 51 publications

Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

Inorganic-ligand exchanging time effect in PbS quantum dot solar cell

Synthesis of Nanoamorphous Germanium and Its Transformation to Nanocrystalline Germanium

Twinned silicon and germanium nanocrystals: Formation, stability and quantum confinement

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