A Computational Predictive Approach for Controlling the Morphology of Functional Molecular Aggregates on Substrates

Structural transition in the single layer growth of diindenoperylene on silica

When forming a film on a substrate, rod shaped organic molecules can order in lying-down or standing-up phases. We have studied the growth of diindenoperylene films on amorphous silicon dioxide by means of molecular dynamics simulations and analyzed the film structure. The vapor deposition process was emulated by depositing single molecules at a fixed rate on the substrate. At 400 K, we observed a transition from disordered lying-down to standing-up molecules, which agrees well with experimental observations. This transition, which depends sensitively on the kinetic parameters, requires both a sufficiently high thermal energy to overcome the energy barrier and a sufficiently large cluster size. Our results indicate that a higher degree of initial disorder in the lying-down phase results in a larger probability for the system to undergo the transition to the standing-up phase.

On the Nature of Charge-Injecting Contacts in Organic Field-Effect Transistors

Organic field-effect transistors (OFETs) are key enabling devices for plastic electronics technology, which has a potentially disruptive impact on a variety of application fields, such as health, safety, and communication. Despite the tremendous advancements in understanding the OFET working mechanisms and device performance, further insights into the complex correlation between the nature of the charge-injecting contacts and the electrical characteristics of devices are still necessary. Here, an in-depth study of the metal-organic interfaces that provides a direct correlation to the performance of OFET devices is reported. The combination of synchrotron X-ray spectroscopy, atomic force microscopy, electron microscopy, and theoretical simulations on two selected electron transport organic semiconductors with tailored chemical structures allows us to gain insights into the nature of the injecting contacts. This multiple analysis repeated at the different stages of contact formation provides a clear picture on the synergy between organic/metal interactions, interfacial morphology, and structural organization of the electrode. The simultaneous synchrotron X-ray experiments and electrical measurements of OFETs in operando uncovers how the nature of the charge-injecting contacts has a direct impact on the injection potential of OFETs.

Noncovalent passivation of supported phosphorene for device applications: from morphology to electronic properties

Simulations suggest efficient routes for the non-covalent passivation of supported phosphorene with alkanes, highlighting strategies to prevent surface degradation phenomena.