Reducing Strain and Fracture of Electrophoretically Deposited CdSe Nanocrystal Films. I. Postdeposition Infusion of Capping Ligands

Kramer, Theodore J.; Kumar, Sanat K.; Steigerwald, Michael L.; Herman, Irving P.

doi:10.1021/jp305607t

Cited by 11 publications

(16 citation statements)

References 33 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We found that films exhibited significant cracking when nanocrystals were precipitated with more than 2.0 mL of ethanol/g of reaction product. Antisolvent precipitation is commonly used to purify nanocrystals , and is known to strip ligands from the nanocrystal surface in many cases. − TGA of the CIGS nanocrystals showed that OLA ligand coverage was significantly affected by the amount of ethanol used in the purification step. In Figure , the weight loss event near 200 °C corresponds to the loss of OLA from the sample, and the total weight loss from the sample provides a measure of the amount of ligand coverage on the nanocrystals.…”

Section: Resultsmentioning

confidence: 99%

“…Without capping ligands on the nanocrystals, there is only weak van der Waals attraction between the inorganic cores holding the particle film together to resist cracking. Kramer et al 52 proposed that higher ligand coverage on nanocrystals can increase the toughness of a dried nanocrystal film and reduce the likelihood of crack formation during the drying process by enhancing the interparticle attraction and strengthening the ligand−ligand interactions by interdigitation and tangling between ligands on neighboring nanocrystals. 54 Additional free ligand in the dried film does not play the same role, because the ligand is not attached to the core of the nanocrystals and does not provide a robust link needed to significantly enhance the interparticle attractions or influence the integrity of the nanocrystal film.…”

Section: ■ Experimental Detailsmentioning

confidence: 99%

See 1 more Smart Citation

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se₂ Nanocrystals

Harvey

Bonafé

Updegrave

et al. 2018

ACS Appl. Energy Mater.

View full text Add to dashboard Cite

Crack-free films of Cu(In,Ga)Se2 (CIGS) nanocrystals were deposited with uniform thickness (>1 μm) on Mo-coated glass substrates using an ink-based, automated ultrasonic spray process, then selenized and incorporated into photovoltaic devices (PVs). The device performance depended strongly on the homogeneity of the selenized films. Cracks in the spray-deposited films resulted in uneven selenization rates and sintering by creating paths for rapid, uncontrollable selenium (Se) vapor penetration. To make crack-free films, the nanocrystals had to be completely coated with capping ligands in the ink. The selenization rate of crack-free films then depended on the thickness of the nanocrystal layer, the temperature, and duration of Se vapor exposure. Either inadequate or excessive Se exposure leads to poor device performance, generating films that were either partially sintered or exhibited significant accumulation of carbon and selenium. The deposition of uniform nanocrystal films is expected to be important for a variety of electronic and optoelectronic device applications.

show abstract

Section: Resultsmentioning

confidence: 99%

Section: ■ Experimental Detailsmentioning

confidence: 99%

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se₂ Nanocrystals

Harvey

Bonafé

Updegrave

et al. 2018

ACS Appl. Energy Mater.

View full text Add to dashboard Cite

show abstract

“…3(a))31. These features act as natural feedbacks to the propagation of light, and random lasing can be observed from the cracks.…”

Section: Resultsmentioning

confidence: 99%

Assembling Ordered Nanorod Superstructures and Their Application as Microcavity Lasers

Liu

Singh

Guo

et al. 2017

Sci Rep

View full text Add to dashboard Cite

Herein we report the formation of multi-layered arrays of vertically aligned and close packed semiconductor nanorods in perfect registry at a substrate using electric field assisted assembly. The collective properties of these CdSexS1-x nanorod emitters are harnessed by demonstrating a relatively low amplified spontaneous emission (ASE) threshold and a high net optical gain at medium pump intensity. The importance of order in the system is highlighted where a lower ASE threshold is observed compared to disordered samples.

show abstract

“…It is important to distinguish the cracking highlighted in this work from earlier studies of NC film cracking, which have shown random cracking (similar to mud cracks) and anisotropic cracking, but the latter only when induced by an applied stimulus. ,− In these examples, crack pattern formation follows naturally from applied stress (most often due to drying), typically nucleating from a top or bottom surface and extending throughout the thickness of the film. Importantly, it is not related to the underlying crystal structure, NC superlattice axes, or grain boundaries.…”

mentioning

confidence: 85%

Anisotropic Cracking of Nanocrystal Superlattices

Diroll

et al. 2017

Nano Lett.

View full text Add to dashboard Cite

The synthesis colloidal nanocrystals in nonpolar organic solvents has led to exceptional size- and shape-control, enabling the formation of nanocrystal superlattices isostructural to atomic lattices built with nanocrystals rather than atoms. The long aliphatic ligands (e.g., oleic acid) used to achieve this control separate nanocrystals too far in the solid state for most charge-transporting devices. Solid-state ligand exchange, which brings particles closer together and enhances conductivity, necessitates large changes in the total volume of the solid (compressive stress), which leads to film cracking. In this work, truncate octahedral lead selenide nanocrystals are shown to self-assemble into body-centered cubic superlattices in which the atomic axes of the individual nanocrystals are coaligned with the crystal axes of the superlattice. Due to this coalignment, upon ligand exchange of the superlattices, cracking is preferentially observed on ⟨011⟩ superlattice directions. This observation is related to differences in the ligand binding to exposed {100} and {111} planes of the PbSe nanocrystal surfaces. This result has implications for binary and more complex structures in which differential reactivity of the constituent elements can lead to disruption of the desired structure. In addition, cracks in PbSe superlattices occur in a semiregular spacings inversely related to the superlattice domain size and strongly influenced by the presence of twin boundaries, which serve as both emission centers and propagation barriers for fractures. This work shows that defects, similar to behavior in nanotwinned metals, could be used to engineer enhanced mechanical strength and electrical conductivity in nanocrystal superlattices.

show abstract

Reducing Strain and Fracture of Electrophoretically Deposited CdSe Nanocrystal Films. I. Postdeposition Infusion of Capping Ligands

Cited by 11 publications

References 33 publications

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se₂ Nanocrystals

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se₂ Nanocrystals

Assembling Ordered Nanorod Superstructures and Their Application as Microcavity Lasers

Anisotropic Cracking of Nanocrystal Superlattices

Contact Info

Product

Resources

About

Reducing Strain and Fracture of Electrophoretically Deposited CdSe Nanocrystal Films. I. Postdeposition Infusion of Capping Ligands

Cited by 11 publications

References 33 publications

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se2 Nanocrystals

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se2 Nanocrystals

Assembling Ordered Nanorod Superstructures and Their Application as Microcavity Lasers

Anisotropic Cracking of Nanocrystal Superlattices

Contact Info

Product

Resources

About

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se₂ Nanocrystals

Uniform Selenization of Crack-Free Films of Cu(In,Ga)Se₂ Nanocrystals