Sohee Jeong

Chemically synthesized InP nanocrystals (NCs) are drawing a large interest as a potentially less toxic alternative to CdSe-based nanocrystals. With a bulk band gap of 1.35 eV and an exciton Bohr radius of ∼10 nm the emission wavelength of InP NCs can in principle be tuned throughout the whole visible and near-infrared range by changing their size. Furthermore, a few works reported fluorescence quantum yields exceeding 70% after overcoating the core NCs with appropriate shell materials. Therefore

Ambient stability of colloidal nanocrystal quantum dots (QDs) is imperative for low-cost, high-efficiency QD photovoltaics. We synthesized air-stable, ultrasmall PbS QDs with diameter (D) down to 1.5 nm, and found an abrupt transition at D ≈ 4 nm in the air stability as the QD size was varied from 1.5 to 7.5 nm. X-ray photoemission spectroscopy measurements and density functional theory calculations reveal that the stability transition is closely associated with the shape transition of oleate-ca

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTHighly Stable Cesium Lead Halide Perovskite Nanocrystals through in Situ Lead Halide Inorganic PassivationJu Young Woo†‡, Youngsik Kim‡§, Jungmin Bae#, Tae Gun Kim∥#, Jeong Won Kim∥#, Doh C. Lee*†, and Sohee Jeong*‡§View Author Information† Department of Chemical and Biomolecular Engineering (BK21+ Program), KAIST Institute for the NanoCentury, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 305-701, Korea‡ Nano-Convergence Re

While interesting and unprecedented material characteristics of two dimensionality (2-D) layered nanomaterials are emerging, their reliable synthetic methodologies are not well developed. In this study we demonstrate general applicability of synthetic protocols to a wide range of colloidal 2-D layered transition-metal chalcogenide (TMC) nanocrystals. As distinctly different from other nanocrystals, we discovered that 2-D layered TMC nanocrystals are unstable in the presence of reactive radicals

We study the effect of thiols on the emission efficiency of aqueous CdSe/ZnS core/shell nanocrystal quantum dots (NQDs). We observe that the impact of thiol addition on emission quantum yields (QYs) is time-, concentration-, and pH-dependent. Further, we use a combination of time-resolved spectroscopic methods to determine the mechanism by which thiol addition can cause either increases or decreases in QYs. Specifically, through transient absorption measurements, we show that thiol addition can

The fast degradation of lead selenide (PbSe) nanocrystal quantum dots (NQDs) in ambient conditions impedes widespread deployment of the highly excitonic, thus versatile, colloidal NQDs. Here we report a simple in situ post-synthetic halide salt treatment that results in size-independent air stability of PbSe NQDs without significantly altering their optoelectronic characteristics. From TEM, NMR, and XPS results and DFT calculations, we propose that the unprecedented size-independent air stabilit

Simple and effective generation of transition metal chalcogenides (TMCs) in a single-layer form has been a challenging task. Here we present a tandem molecular intercalation (TMI) as a new exfoliation concept for producing single-layer TMCs from multi-layer colloidal TMC nanostructures in solution phase. TMI requires tandem Lewis base intercalates, where short ‘initiator’ molecules first intercalate into TMCs to open up the interlayer gap, and the long ‘primary’ molecules then bring the gap to f

Colloidal quantum dots (QDs) are nanosized semiconductors whose electronic features are dictated by the quantum confinement effect. The optical, electrical, and chemical properties of QDs are influenced by their dimensions and surface landscape. The surface of II-VI and IV-VI QDs has been extensively explored; however, in-depth investigations on the surface of III-V QDs are still lagging behind. This Perspective discusses the current understanding of the surface of III-V QDs, outlines deep trap

Wet chemical synthesis of covalent III-V colloidal quantum dots (CQDs) has been challenging because of uncontrolled surfaces and a poor understanding of surface-ligand interactions. We report a simple acid-free approach to synthesize highly crystalline indium phosphide CQDs in the unique tetrahedral shape by using tris(dimethylamino) phosphine and indium trichloride as the phosphorus and indium precursors, dissolved in oleylamine. Our chemical analyses indicate that both the oleylamine and chlor

We introduce indium arsenide colloidal quantum dot films for photovoltaic devices, fabricated by two-step surface modification. Native ligands and unwanted oxides on the surface are peeled off followed by passivating with incoming atomic or short ligands. The near-infrared-absorbing n-type indium arsenide colloidal quantum dot films can be tuned in energy-level positions up to 0.4 eV depending on the surface chemistry, and consequently, they boost collection efficiency when used in various emerg

We developed a single step, cation-exchange reaction that produces air-stable PbSe quantum dots (QDs) from ZnSe QDs and PbX2 (X = Cl, Br, or I) precursors. The resulting PbSe QDs are terminated with halide anions and contain residual Zn cations. We characterized the PbSe QDs using UV-vis-NIR absorption, photoluminescence quantum yield spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. Solar cells fabricated from these PbSe QDs obtained an ove

Abstract Wet chemical synthesis of covalent III‐V colloidal quantum dots (CQDs) has been challenging because of uncontrolled surfaces and a poor understanding of surface–ligand interactions. We report a simple acid‐free approach to synthesize highly crystalline indium phosphide CQDs in the unique tetrahedral shape by using tris(dimethylamino) phosphine and indium trichloride as the phosphorus and indium precursors, dissolved in oleylamine. Our chemical analyses indicate that both the oleylamine

Abstract Highly monodisperse colloidal InAs quantum dots (QDs) with superior optoelectronic properties are promising candidates for various applications, including infrared photodetectors and photovoltaics. Recently, a synthetic process involving continuous injection has been introduced to synthesize uniformly sized InAs QDs. Still, synthetic efforts to increase the particle size of over 5 nm often suffer from growth suppression. Secondary nucleation or interparticle ripening during the growth a

ADVERTISEMENT RETURN TO ISSUEPREVCommunicationNEXTTuning Size and Size Distribution of Colloidal InAs Nanocrystals via Continuous Supply of Prenucleation Clusters on Nanocrystal SeedsSudarsan Tamang†‡, Sunghee Lee†, Hyekyoung Choi†§, and Sohee Jeong*†§View Author Information† Department of Nanomechatronics, Korea Institute of Machinery and Materials, Daejeon 34103, Korea‡ Department of Chemistry, Sikkim University, Gangtok, Sikkim 737102, India§ Department of Nanomechatronics, Korea University o

We developed a new chemical strategy to enhance the stability of lead selenide nanocrystals (PbSe NCs) against oxidation through the surface passivation by P-O- moieties. In the synthesis of PbSe NCs, tris(diethylamino)phosphine (TDP) selenide (Se) was used as a Se precursor, and the resulting PbSe NCs withstood long-term air exposure while showing nearly no sign of oxidation. Nuclear magnetic resonance (NMR) spectroscopy reveals that TDP derivatives passivate the surface of PbSe NC. Through a s