Crystalline organic thin films for crystalline OLEDs (I): orientation of phenanthroimidazole derivatives

Compared to traditional organic light-emitting diodes (OLEDs) based on amorphous thin films, crystalline OLEDs possess promising advantages in developing advanced display technologies, such as longer life time and lower driving...

In-situ analysis of growth rate evolution during molecular layer deposition of ultra-thin polyurea films using aliphatic and aromatic precursors

Organic thin films formed by molecular layer deposition (MLD) are important for next-generation electronics, energy storage, photoresists, protective barriers and other applications. This study uses in situ ellipsometry and quartz...

indexGIXS – software for visualizing and interactive indexing of grazing-incidence scattering data

Grazing incidence small- and wide-angle scattering (GISAXS, GIWAXS) are widely applied for the study of organic thin films, be it for the characterization of nanostructured morphologies in block copolymers, nanocomposites, or nanoparticle assemblies, or the packing and orientation of small aromatic molecules and conjugated polymers. Organic thin films typically are uniaxial powders, with specific crystallographic planes oriented parallel to the substrate surface. The associated fiber texture scattering patterns are complicated by refraction corrections and multiple scattering. We present an interactive graphics tool to index such patterns.

Ultrasmooth Organic Films Via Efficient Aggregation Suppression by a Low-Vacuum Physical Vapor Deposition

Organic thin films with smooth surfaces are mandated for high-performance organic electronic devices. Abrupt nucleation and aggregation during film formation are two main factors that forbid smooth surfaces. Here, we report a simple fast cooling (FC) adapted physical vapor deposition (FCPVD) method to produce ultrasmooth organic thin films through effectively suppressing the aggregation of adsorbed molecules. We have found that thermal energy control is essential for the spread of molecules on a substrate by diffusion and it prohibits the unwanted nucleation of adsorbed molecules. FCPVD is employed for cooling the horizontal tube-type organic vapor deposition setup to effectively remove thermal energy applied to adsorbed molecules on a substrate. The organic thin films prepared using the FCPVD method have remarkably ultrasmooth surfaces with less than 0.4 nm root mean square (RMS) roughness on various substrates, even in a low vacuum, which is highly comparable to the ones prepared using conventional high-vacuum deposition methods. Our results provide a deeper understanding of the role of thermal energy employed to substrates during organic film growth using the PVD process and pave the way for cost-effective and high-performance organic devices.

Grazing-incidence X-ray diffraction tomography for characterizing organic thin films

Characterization of thin films is of paramount importance for evaluating material processing outcomes/efficiency as well as establishing structure–property/performance relationships. This article introduces grazing-incidence diffraction tomography (GID tomography), a technique that combines grazing-incidence X-ray scattering and computed tomography to quantitatively determine the dimension and orientation of crystalline domains in thin films without restrictions on the beam coherence, substrate type or film thickness. This computational method extends the capability of synchrotron beamlines by utilizing standard X-ray scattering experiment setups.

indexGIXS – software for visualizing and interactive indexing of grazing-incidence scattering data

Grazing incidence small- and wide-angle scattering (GISAXS, GIWAXS) are widely applied for the study of organic thin films, be it for the characterization of nanostructured morphologies in block copolymers, nanocomposites, or nanoparticle assemblies, or the packing and orientation of small aromatic molecules and conjugated polymers. Organic thin films typically are uniaxial powders, with specific crystallographic planes oriented parallel to the substrate surface. The associated fiber texture scattering patterns are complicated by refraction corrections and multiple scattering. We present an interactive graphics tool to index such patterns.