Toward More Efficient Organic Semiconductors: The Relationship between Morphology, Charge Transport, and Photophysical Properties

Abstract

In recent years, materials science has been facing an electronics revolution due to the fast progress in the development of organic semiconductors. In this context, the current study attempts to tune the photophysical properties of polycyclic aromatic hydrocarbons (PAHs) by engineering their morphology and size. Four families of PAHs─oligoacenes, circulenes, triangulenes, and sunflowers─are considered to investigate the evolution of their optoelectronic properties with size and morphology. Based on the calculated properties, several quantitative structure–property relationships have been established for the prediction of reorganization energy. It is found that morphologies like circulene and triangulene that are less aromatic and have smaller energy gaps achieve smaller reorganization energy and thus are better candidates for charge transport materials. For all considered PAHs, the excitation energies of the strongest low-lying electronic transition (β peak) span in the visible region and demonstrate the size tunability. The β peak of some oligoacene and triangulene families exhibits plasmonic behavior that is important for the fabrication of lighter optical devices compared with metallic systems. We have also explored the effect of sulfur heteroatoms on the structural, electronic, and optical properties of circulene and sunflower morphologies.