Polymorphism and structure formation in copper phthalocyanine thin films.

Many polymorphic crystal structures of copper phthalocyanine (CuPc) have been reported over the past few decades, but despite its manifold applicability, the structure of the frequently mentioned α polymorph remained unclear. The base-centered unit cell (space group 2/) suggested in 1966 was ruled out in 2003 and was replaced by a primitive triclinic unit cell (space group 1). This study proves unequivocally that both α structures coexist in vacuum-deposited CuPc thin films on native silicon oxide by reciprocal space mapping using synchrotron radiation in grazing incidence.

Structural order enhances charge carrier transport in self-assembled Au-nanoclusters.

The collective properties of self-assembled nanoparticles with long-range order bear immense potential for customized electronic materials by design. However, to mitigate the shortcoming of the finite-size distribution of nanoparticles and thus, the inherent energetic disorder within assemblies, atomically precise nanoclusters are the most promising building blocks. We report an easy and broadly applicable method for the controlled self-assembly of atomically precise Au(BuP)Cl nanoclusters into micro-crystals.

Surface-Controlled Crystal Alignment of Naphthyl End-Capped Oligothiophene on Graphene: Thin-Film Growth Studied by in Situ X-ray Diffraction.

We report on the microstructure, morphology, and growth of 5,5'-bis(naphth-2-yl)-2,2'-bithiophene (NaT2) thin films deposited on graphene, characterized by grazing incidence X-ray diffraction (GIXRD) and complemented by atomic force microscopy (AFM) measurements. NaT2 is deposited on two types of graphene surfaces: custom-made samples where chemical vapor deposition (CVD)-grown graphene layers are transferred onto a Si/SiO substrate by us and common commercially transferred CVD graphene on Si/SiO. Pristine Si/SiO substrates are used as a reference.

Reorientation of π-conjugated molecules on few-layer MoS films.

Small π-conjugated organic molecules have attracted substantial attention in the past decade as they are considered as candidates for future organic-based (opto-)electronic applications. The molecular arrangement in the organic layer is one of the crucial parameters that determine the efficiency of a given device. The desired orientation of the molecules is achieved by a proper choice of the underlying substrate and growth conditions.

Revealing Structure and Crystallographic Orientation of Soft Epitaxial Assembly of Nanocrystals by Grazing Incidence X-ray Scattering.

We study the structural coherence of a self-assembled overlayer of PbS nanocrystal (NC) superlattice onto an underlying PbS NC monolayer, which acts as a template. We explore the effect of the templating layer on the structure of the overlayer asemblies by varying interfacial strain and determine the impact of new ligands on their superlattice structure. The overlayers and templates are analyzed by grazing-incidence X-ray scattering and microscopy.

Evaluation of low-cadmium ZnCdSeS alloyed quantum dots for remote phosphor solid-state lighting technology.

We report on the possibility to enhance color rendering of commercially available remote phosphor light-emitting diode modules by using low-cadmium content ZnCdSeS alloyed quantum dots. The employed numerical simulations showed that the color-rendering index of 90+ at the color-correlated temperature of 3200 K can be achieved by application of a single layer of quantum dots onto a neutral-white remote phosphor substrate. The experimental results fully support the numerical calculations, thus revealing the only limiting factor in achieving a higher photometric performance: the self-absorption effect in quantum dots.