Enhanced Multiple Exciton Generation in PbS|CdS Janus-like Heterostructured Nanocrystals.

Generating multiple excitons by a single high-energy photon is a promising third-generation solar energy conversion strategy. We demonstrate that multiple exciton generation (MEG) in PbS|CdS Janus-like heteronanostructures is enhanced over that of single-component and core/shell nanocrystal architectures, with an onset close to two times the PbS band gap. We attribute the enhanced MEG to the asymmetric nature of the heteronanostructure that results in an increase in the effective Coulomb interaction that drives MEG and a reduction of the competing hot exciton cooling rate.

Synthesis and Spectroscopy of Silver-Doped PbSe Quantum Dots.

Electronic impurity doping of bulk semiconductors is an essential component of semiconductor science and technology. Yet there are only a handful of studies demonstrating control of electronic impurities in semiconductor nanocrystals. Here, we studied electronic impurity doping of colloidal PbSe quantum dots (QDs) using a postsynthetic cation exchange reaction in which Pb is exchanged for Ag.

Quantum dot-induced phase stabilization of α-CsPbI3 perovskite for high-efficiency photovoltaics.

We show nanoscale phase stabilization of CsPbI quantum dots (QDs) to low temperatures that can be used as the active component of efficient optoelectronic devices. CsPbI is an all-inorganic analog to the hybrid organic cation halide perovskites, but the cubic phase of bulk CsPbI (α-CsPbI)-the variant with desirable band gap-is only stable at high temperatures. We describe the formation of α-CsPbI QD films that are phase-stable for months in ambient air.

All-Inorganic Germanium Nanocrystal Films by Cationic Ligand Exchange.

We introduce a new paradigm for group IV nanocrystal surface chemistry based on room temperature surface activation that enables ionic ligand exchange. Germanium nanocrystals synthesized in a gas-phase plasma reactor are functionalized with labile, cationic alkylammonium ligands rather than with traditional covalently bound groups. We employ Fourier transform infrared and (1)H nuclear magnetic resonance spectroscopies to demonstrate the alkylammonium ligands are freely exchanged on the germanium nanocrystal surface with a variety of cationic ligands, including short inorganic ligands such as ammonium and alkali metal cations.

Preparation of Cd/Pb Chalcogenide Heterostructured Janus Particles via Controllable Cation Exchange.

We developed a strategy for producing quasi-spherical nanocrystals of anisotropic heterostructures of Cd/Pb chalcogenides. The nanostructures are fabricated via a controlled cation exchange reaction where the Cd(2+) cation is exchanged for the Pb(2+) cation. The cation exchange reaction is thermally activated and can be controlled by adjusting the reaction temperature or time.

Cu(2)ZnSnS(4) nanocrystal dispersions in polar liquids.

Cu(2)ZnSnS(4) (CZTS) nanocrystals sterically stabilized with oleic acid and oleylamine ligands and dispersed in nonpolar organic liquids have been extracted into, and electrostatically stabilized in, polar liquids by covering their surfaces with S(2-).

Photoelectrochemical activity of as-grown, α-Fe2O3 nanowire array electrodes for water splitting.

Undoped hematite nanowire arrays grown using plasma oxidation of iron foils show significant photoactivity (~0.38 mA cm(-2) at 1.5 V versus reversible hydrogen electrode in 1 M KOH).