Impact of Intermolecular Interactions Between a Diketopyrrolopyrrole-Based Conjugated Polymer and Bromobenzaldehyde on Field-Effect Transistors

In this study, intermolecular interactions were investigated for increasing the charge carrier mobility of organic field-effect transistors (OFETs) based on a conjugated polymer. A diketopyrrolopyrrole (DPP)-based conjugated polymer widely used in OFETs, i.e., poly[2,5-(2-octyldodecyl)-3,6-diketopyrrolopyrrole-alt-5,5-(2,5-di(thien-2-yl)thieno[3,2-b]thiophene)] (PDPP-DTT), was assembled using 2-bromobenzaldehyde (2-BBA) and used as an active layer for OFETs. Morphological characterization and analysis for non-covalent intermolecular interactions suggested that the halogen bonding between the bromide of 2-BBA and electron-donor group of PDPP-DTT and the association between the electron-acceptor group in 2-BBA and sulfur of PDPP-DTT improved the hole transfer in the PDPP-DTT-based OFETs. The intermolecular interactions resulting from the addition of 2-BBA contributed to the two-fold enhancement of the hole mobility, two-order increase in magnitude of the current on/off ratio, and 50% decrease in the threshold voltage of the OFETs based on PDPP-DPP.