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

摘要

The molecular packing and resultant charge transport behaviors of semiconductingpolymers are widely known to be temperature-dependent. Due to thelimitation of measurement methods, previous studies on molecular packingbehavior have been mainly focused on a very limited temperature range, andtherefore cannot support the understanding of charge transport behaviors. Inthis study, with a homemade temperature-dependent grazing incidence XRDmeasurement chamber, the relationship between molecular packing structureand charge transport properties of diketopyrrolopyrrole-based polymers isinvestigated across a wide temperature range of 98–623 K. Glass transitiontemperatures of the alkyl side-chain and aromatic backbone are identifiedthrough the observation of clear transitions in the thermal expansion coefficientsof d?d packing and π?π stacking, respectively. A correlation betweenthe π?π stacking distance and charge transport properties is then establishedusing an extended Miller?Abrahams model. The turning point of the chargetransport and the failure of the polymer-based devices are proved to becaused by packing structure changes due to increased temperatures. Such anexamination over a wide range of temperatures improves the understandingof the charge transport properties of semiconducting polymers and helpsconstruct thermally stable devices to be used in extreme conditions.