We demonstrate that metal carboxylate complexes (L-M(O2CR)2, R = oleyl, tetradecyl, M Cd, Pb) are readily displaced from carboxylate-terminated ME nanocrystals (ME CdSe, CdS, PbSe, PbS) by various Lewis bases (L tri-n-butylamine, tetrahydrofuran, tetradecanol, N,N-dimethyl-n-butylamine, tri-n-butylphosphine, N,N,N',N'-tetramethylbutylene-1,4-diamine, pyridine, N,N,N',N'-tetramethylethylene-1,2-diamine, n-octylamine). The relative displacement potency is measured (1)H NMR spectroscopy and...

Abstract Thin films based on two-dimensional metal halide perovskites have achieved exceptional performance and stability in numerous optoelectronic device applications. Simple solution processing of the 2D perovskite provides opportunities for manufacturing devices at drastically lower cost compared to current commercial technologies. A key high is align layers, during processing, vertical electrodes achieve efficient charge transport. However, it yet be understood how counter-intuitive...

We report the design, fabrication, and characterization of colloidal PbSe nanocrystal (NC)-based photovoltaic test structures that exhibit an excitonic solar cell mechanism. Charge extraction from NC active layer is driven by a photoinduced chemical potential energy gradient at nanostructured heterojunction. By minimizing perturbation to levels thereby gaining insight into "intrinsic" properties charge transfer mechanism NC, we show direct correlation between interfacial level offsets device...

We report the structure of methylammonium lead(II) iodide perovskite in mesoporous TiO2, as used high-performance solar cells. Pair distribution function analysis X-ray scattering reveals a two component nanostructure: one with medium range crystalline order (30 atom %) and another only local structural coherence (70 %). The nanostructuring correlates blueshift absorption onset increases photoluminescence. Our findings underscore importance fully characterizing controlling for improved cell...

The colloidal synthesis of SnSe nanoparticles is accomplished through the injection bis[bis(trimethylsilyl)amino]tin(II) into hot trioctylphosphine:selenium in presence oleylamine. Through manipulation reaction temperature particles are grown with average diameter reliably tuned to 4-10 nm. Quantum confinement examined by establishing a relationship between particle size and band gap while depth growth dynamics illuminated UV-vis-NIR spectroscopy. Surface chemistry effects explored,...

In a photovoltaic perovskite, entropy-driven structural transition enables kinetic trapping of desired phase.

Density functional calculations for the binding energy of oleic acid-based ligands on Pb-rich {100} and {111} facets PbSe nanocrystals determine surface energies as a function ligand coverage. Oleic acid is expected to bind nanocrystal in form lead oleate. The Wulff construction predicts thermodynamic equilibrium shape nanocrystals. coverage, which can be controlled by changing concentration during synthesis. different results coverages facets, transition from octahedral cubic predicted when...

Rotational dynamics of organic cations in the CH₃NH₃PbI₃perovskite are revealed by elastic and quasi-elastic neutron scattering group theoretical analysis.

Temperature dependent energy levels of methylammonium lead iodide are investigated using a combination ultraviolet photoemission spectroscopy and optical spectroscopy. Our results show that the valence band maximum conduction minimum shift down in by 110 meV 77 as temperature increases from 28 °C to 85 °C. Density functional theory calculations slab structures decreased orbital splitting due thermal expansion is major contribution experimentally observed levels. have implications for solar...

The assembly of colloidal nanocrystals (NCs) into superstructures with long-range translational and orientational order is sensitive to the molecular interactions between ligands bound NC surface. We illustrate how ligand coverage on PbS NCs can be exploited as a tunable parameter direct self-assembly superlattices predefined symmetry. show that dense assemble face-centered cubic (fcc) whereas sparse body-centered (bcc) which also exhibit ordering in their lattice sites. Surface chemistry...

Internanocrystal coupling induced excitons dissociation in lead salt nanocrystal assemblies is investigated. By combining transient photoluminescence spectroscopy, grazing incidence small-angle X-ray scattering, and time-resolved electric force microscopy, we show that can dissociate, without the aid of an external bias or chemical potential gradient, via tunneling through a barrier when energy comparable to exciton binding energy. Our results have important implications for design...

Despite intense research efforts by groups worldwide, the potential of self-assembled nanocrystal superlattices (NCSLs) has not been realized due to an incomplete understanding fundamental molecular interactions governing self-assembly process. Because NCSLs reside naturally at length-scales between atomic crystals and colloidal assemblies, synthetic control over properties constituent (NC) building blocks their coupling in ordered assemblies is expected yield a new class materials with...

Significance Hybrid organic–inorganic perovskites (HOIPs) are among the most promising materials for next-generation solar cells that combine high efficiency and low cost. The record of HOIP-based has reached above 22%, which is comparable to silicon cells. HOIP can be manufactured using simple solution processing methods drastically cheaper than current commercial cell technologies. Despite progress so far, microscopic mechanism in HOIPs yet understood. Our study shows rotation organic...

Solution-processed tandem solar cells created from nanocrystal quantum dots with size-tuned energy levels are demonstrated. Prototype devices featuring interconnected dot layers of cascaded gaps exhibit IR sensitivity and an open circuit voltage, Voc, approaching 1 V. The cell performance depends critically on the optical electrical properties interlayer. Detailed facts importance to specialist readers published as ”Supporting Information”. Such documents peer-reviewed, but not copy-edited...

Impact of rationally selected additives in precursor solutions on the nucleation and growth hybrid perovskite thin films is investigated.

Metal halide perovskites have demonstrated strong potential for optoelectronic applications. Particularly, two-dimensional (2D) emerged to be promising materials due their tunable properties and superior stability compared three-dimensional counterparts. For high device performance, 2D need a vertical crystallographic orientation with respect the electrodes achieve efficient charge transport. However, is difficult various compositions lack of understanding thin film nucleation growth...

Halide dealloying in CsPbBrI2 perovskite solar cells proves to be critical achieving high performance. This occurs under steady illumination and is a reversible process, suggesting transitions between equilibrium states dark illuminated environments. Through decoupling charge collection the electron- hole-transporting layers, our photoluminescence, X-ray diffraction, cell device characterization results suggest that light-induced halide improves hole cells, resulting increased efficiency...

We report on the thermal conductivities of two-dimensional metal halide perovskite films measured by time domain thermoreflectance. Depending molecular substructure ammonium cations and owing to weaker interactions in layered structures, our hybrid perovskites range from 0.10 0.19 W m-1 K-1, which is drastically lower than that their three-dimensional counterparts. use dynamics simulations show organic component induces a reduction stiffness sound velocities along with giving rise...

CuO is an earth-abundant, nontoxic, and low band-gap material; hence it attractive candidate for application in solar cells. In this paper, a synthesis of nanocrystals by facile alcohothermal route reported. The are dispersible solvent mixture methanol chloroform, thus enabling the processing solution. A bilayer cell comprising phenyl-C61-butyric acid methyl ester (PCBM) achieved power conversion efficiency 0.04%, indicating potential material light-harvesting applications.

The self-assembly of colloidal nanocrystals into ordered superstructures depends critically on the shape nanocrystal building blocks. We investigated cubic PbSe from suspensions in real-time using situ synchrotron-based X-ray scattering. combined small-angle and wide-angle scattering to investigate translational ordering their orientational lattice sites, respectively. found that assembled a face-up (i.e., ⟨100⟩ normal interface) configuration at liquid/substrate interface whereas nanocubes...

Preferential crystallographic orientation can propagate through metal halide perovskite thin films.

Hybrid organic-inorganic perovskites, as well the perovskites in general, are known for their phase complexity evidenced by stabilization of different polymorphs, and thus an understanding regions stability transitions can be important photovoltaic optoelectronic technologies. Here we use a multiscale approach based on first-principles calculations with van der Waals corrections classical force-field molecular dynamics to determine finite-temperature properties tetragonal cubic phases...

We investigated the influence of processing conditions, nanocrystal/substrate interactions and solvent evaporation rate on ordering strongly interacting nanocrystals by synergistically combining electron microscopy synchrotron-based small-angle X-ray scattering analysis. Spin-cast PbSe nanocrystal films exhibited submicrometer-sized supracrystals with face-centered cubic symmetry (001)s planes aligned parallel to substrate. The drop-cast lead salt was sensitive nature substrate dynamics....

Transfer of photoexcited charge from PbS nanocrystals to ligand molecules is investigated in different solvents. We find that the transfer rate increases dramatically with solvent dielectric constant. This trend accounted for by a modified Marcus theory incorporates only static effects. The choice allows significant control process. As an important example, we dispersed water exhibit rates 1000 times higher than same organic solvent. Rapid extraction will be efficient nanocrystal-based...