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

Abstract

The 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.

Capturing the Phase Transformation and Thermal Behavior of P(NDI2OD-T2) with In Situ Grazing Incidence WAXS

“…A similar result was also reported for another donor−acceptor-type conjugated polymer, namely DPP-4T, that the transition temperature determined from the thermal expansion of lamellar stacking is 62 °C lower than that of π−π stacking, which is ascribed to the difference in glass transition temperatures between the side chain and backbone. 33 For the P(NDI2OD-T2) batch in the present study, neither exothermic nor endothermic peaks can be identified from the DSC curve (Figure S9). Nevertheless, a good agreement is found between the π−π transition temperature and the theoretically calculated backbone glass transition temperature (274 °C) using the semiempirical correlation model developed by Xie et al (supplementary note 3 in the Supporting Information).…”

“…Regarding this discrepancy, we speculate that it is due to the different mobility of the stiff backbones and flexible side chains in P­(NDI2OD-T2), with the latter being more mobile, hence exhibiting a lower glass transition temperature. A similar result was also reported for another donor–acceptor-type conjugated polymer, namely DPP-4T, that the transition temperature determined from the thermal expansion of lamellar stacking is 62 °C lower than that of π–π stacking, which is ascribed to the difference in glass transition temperatures between the side chain and backbone . For the P­(NDI2OD-T2) batch in the present study, neither exothermic nor endothermic peaks can be identified from the DSC curve (Figure S9).…”

Alkyl-Substituted N,S-Embedded Heterocycloarenes with a Planar Aromatic Configuration for Hosting Fullerenes and Organic Field-Effect Transistors

“…The results showed that NS-Octulene-3 exhibited thermally activated charge-transport features with the temperature increasing from 20 to 100 °C, , and when the operating temperature further increased, the electrical performance decreased mainly due to thermally induced molecular packing variation, , which was proved by thermogravimetric analysis and variable temperature 2D GI-XRD measurements (Figures S23 and S29). It was found that the packing distance increased obviously, and the molecular stacking structure could hardly be maintained at elevated temperatures, presumably due to the molecular thermodynamic movement (Figure S29), , as a result of which the charge carrier transport becomes more difficult and results in the decreased electrical performance. , …”

“…It was found that the packing distance increased obviously, and the molecular stacking structure could hardly be maintained at elevated temperatures, presumably due to the molecular thermodynamic movement (Figure S29), 24,26 as a result of which the charge carrier transport becomes more difficult and results in the decreased electrical performance. 24,27 ■ CONCLUSIONS…”

Tailoring Rigid Segments in Dopant-Free Polymeric Hole Transport Materials for Perovskite Quantum Dot Solar Cells

“…After 100 °C TA of the polymers, their 2D-GIWAXS peaks became narrower and stronger. However, Zhao et al 47 recently demonstrated that, as the degree of thermal motion increases, the lattice vibrations of the crystalline domain increase, triggering π−π stacking to destroy the packed structures. After 200 °C TA, Asy-PDTS showed an amorphous morphology with the face-on domain totally collapsed.…”