Significant Mobility Enhancement by Semicrystalline Polymers Additive for Crystallization and Charge Transport in Organic Field-effect Transistor

The incorporation of semi-crystalline polymers as additives with small-molecule organic semiconductors has emerged as a pioneering method for the alteration of crystallization processes, thin film morphologies, and charge carrier mobility within organic semiconductor matrices. In this paper, we utilize the intrinsic attributes of polyethylene oxide (PEO), acting as a semi-crystalline polymer additive, to modulate the crystallization, phase segregation and charge transport of 6,13-bis (triisopropylsilyl) pentacene (TIPS pentacene). To understand the synergistic effects between varying molecular weights (8, 100, 300 and 900 K) of PEO and the crystallization behavior of TIPS pentacene, we conducted a quantitative analysis of the films' relative crystallinity and crystallographic morphology employing X-ray diffraction (XRD) and optical microscopy. Our findings indicate that higher molecular weight PEOs (300K and 900K) exhibit reduced molecular chain activity, resulting in lower crystallinity at increased doping ratios. Furthermore, attributes such as a high dielectric constant and a substantial melting point, combined with favorable thermoplastic properties, predispose these films to a more susceptible phase separation within the crystalline matrix. Conversely, films with lower molecular weight PEOs (8 and 100 K) showed lesser impact from molecular chain dynamics, leading to enhanced crystal morphology, higher crystallinity, and improved charge carrier mobility by up to 11 times. This substantial enhancement underscores the potential of employing low molecular weight semi-crystalline polymers as additive agents in the development of advanced organic semiconductor devices.

Graphical Abstract