Molecular Packing and Charge Transport Behaviors of Semiconducting Polymers Over a Wide Temperature Range

Abstract

AbstractThe molecular packing and resultant charge transport behaviors of semiconducting polymers are widely known to be temperature‐dependent. Due to the limitation of measurement methods, previous studies on molecular packing behavior have been mainly focused on a very limited temperature range, and therefore cannot support the understanding of charge transport behaviors. In this study, with a homemade temperature‐dependent grazing incidence XRD measurement chamber, the relationship between molecular packing structure and charge transport properties of diketopyrrolopyrrole‐based polymers is investigated across a wide temperature range of 98–623 K. Glass transition temperatures of the alkyl side‐chain and aromatic backbone are identified through the observation of clear transitions in the thermal expansion coefficients of d−d packing and π−π stacking, respectively. A correlation between the π−π stacking distance and charge transport properties is then established using an extended Miller−Abrahams model. The turning point of the charge transport and the failure of the polymer‐based devices are proved to be caused by packing structure changes due to increased temperatures. Such an examination over a wide range of temperatures improves the understanding of the charge transport properties of semiconducting polymers and helps construct thermally stable devices to be used in extreme conditions.