Final Report Summary - COMPOREL (Large-Scale Computational Screening and Design of Highly-ordered pi-conjugated Molecular Precursors to Organic Electronic)
Organic semiconductors represent an appealing alternative to silicon-based electronics. This new generation of electronic materials offers completely new functionalities (e.g. impact resistance, transparency, flexibility) at reduced fabrication costs. However, the charge mobility and, thus, the performance of these organic devices (e.g. field-effect transistors, light-emitting diodes, photovoltaic cells) remains limited due to heavy dependence on the nature and organization of the π-conjugated organic cores. To achieve full potential, it is critical to identify structural and electronic descriptors pertinent to the charge carrier mobility and establish structure-function relationships describing how these parameters can be modified to enhance a devices’ performance. In this research program, we have elaborated efficient computational schemes and protocols that can accelerate the discovery pace of organic molecular materials. We specifically explore one-dimensional nanofibrils exhibiting tightly packed oligomer arrangements. The following achievements have been made toward accomplishing this goal: (1) Innovative computational techniques have been developed and implemented. These electronic structure approaches aim to improve the description and sampling of large-scale molecular assemblies. While ideally suited for describing finite molecular aggregates and validating our design principles, their field of applicability of these methods will impact the broader community of quantum chemists. (2) An automated procedure has been developed to construct one-dimensional infinite nanofibrils and compute the macroscopic charge transport. Such a protocol enables the detailed comparison of fiber properties and the identification of the most promising candidate molecular nanostructures. (3) From the chemistry point of view, we have formulated design principles, identified structure-property relationships and validated their relevance on real life systems. We have demonstrated that utilization of well-chosen van der Waals aggregators or molecular cores holds promise as a driving force towards the formation of more tightly packed structures that exhibit better stacking arrangement and enhanced transport properties. Our work can serve both as an accelerator for the identification of improved organic semiconductors and as a modern computational platform capable of delivering fundamental information on nanomaterials ranging from the electronic structure at the molecular scale up to macroscopic properties. These advancements should enable the rational design of a new generation of plastic electronic devices.