Growth, structure and templating of anthradithiophene and its β-methylthiolated derivative

Abstract

Organic semiconductor thin films are one of the key components in organic optoelectronics, and their structure, crystallinity, and morphology can significantly influence the properties and performance of the devices that they are used in. The thin film growth behavior of organic semiconductors can be affected by the molecular shape, substituents, growth conditions, and so on. Thus, understanding the growth mechanism and controlling the growth process is challenging, but crucially important. In this work, the thin film growth behaviors of two prototypical organic semiconductors, anthradithiophene (ADT) and its β-methylthiolated derivative (β-MT-ADT), which both have the same molecular backbone, with minor differences, in the substituents, but very different solid-state structures, i.e., herringbone for ADT and rubrene-like “pitched” π-stacking for β-MT-ADT, were studied. The structure of the thin films was investigated using different X-ray diffraction (XRD) techniques, including X-ray reflectivity (XRR) for the out-of-plane structure, and synchrotron-based grazing-incidence wide-angle X-ray scattering (GIWAXS) for the in-plane structure. The morphologies of the thin films were explored with atomic force microscopy (AFM), and their thickness evolution was determined quantitatively within the dynamic scaling framework. In addition, the influence of substrate surface treatment on the thin film growth process of β-MT-ADT was studied using diindenoperylene (DIP) as the templating layer. This paper reports the thin film growth behaviors and structures of two representative organic semiconductors. It offers better understanding of the influence of minor molecular modifications on the thin film growth behavior, providing guidance for future material design and for developing high-performance organic semiconductors based on thin film structure design.