Impact of interface disorder on the crystallization and charge transport of conjugated polymer thin films in organic field-effect transistors

Abstract

This study investigates how interface disorder affects the crystallization of conjugated polymer thin films and the subsequent impact on charge transport in organic field-effect transistors (OFETs). Conjugated polymers are vital in the fabrication of OFETs due to their ability to conduct charge carriers. However, structural disorder at the interfaces of these thin films can significantly disrupt the alignment and arrangement of the polymer chains, leading to irregular and unpredictable diffusion patterns. This disorganized structure impedes the efficient transfer of charge carriers, which is crucial for the optimal performance of OFETs. Our comprehensive analysis employs X-ray scattering methods to accurately determine the crystallization induced by interface disorder in isoindigo-BTBT films, resulting from surface and interface interactions in a non-destructive manner. Analysis of X-ray reflectivity (XRR)-derived electron density profiles reveals the stacking of polymer chains within the middle of the film, accompanied by disordered arrangements at both the air-polymer and polymer-substrate interfaces. To elucidate the origins of interface disorder, we used classical nucleation theory, thickness-dependent XRR studies, and statistical analysis of surface morphology at various annealing temperatures. Furthermore, fabricating bottom gate top contact OFETs revealed reduced field effect mobility with increased disorder. This highlights the need to address disorder at the polymer-substrate interface to improve charge transport efficiency in these devices. By understanding and mitigating the effects of disorder at the semiconductor–dielectric interface, we can enhance the performance of OFETs, paving the way for more reliable and efficient organic electronic devices.