Ordering of Poly(3-hexylthiophene) in Solutions and Films: Effects of Fiber Length and Grain Boundaries on Anisotropy and Mobility

Abstract

Long-range ordering emerges in poly­(3-hexylthiophene) (P3HT) solutions during time-dependent aggregation. Here, aggregation of P3HT in chloroform solution was induced by ultrasonication, aging, and combinations thereof. UV–vis spectroscopy and polarized optical microscopy demonstrated that long-range ordering in the solution and subsequently the solid state depends on assembled P3HT fiber length, as determined by film atomic force microscopy. Ultrasonication induced the formation of fibers that were relatively short compared to those obtained through aging. As a result, ultrasonication afforded isotropic solutions and films, whereas aging afforded anisotropic solutions and films. The impact of fiber length and anisotropy on macroscopic charge transport performance was evaluated using an organic field-effect transistor (OFET) architecture. Both aged and sonicated solutions exhibited charge carrier mobilities that were an order of magnitude higher than that obtained for pristine samples. Aging of sonicated solutions enabled semiconducting thin films with significantly higher mobilities (1.5 × 10–1 cm2 V–1 s–1) than those of either solution processing technique. Furthermore, the results indicate that grain boundary morphology has a significant impact on macroscopic charge carrier mobility. Grazing incidence wide-angle X-ray scattering demonstrated that the combined sonication/aging method affords a solidified film where the semiconductor exhibits a highly edge-on orientation. The results suggest that the nucleation and growth of aggregates can be controlled via solution processing methods and thus may allow the manipulation of active layer orientation, crystal packing density, and crystallite size. The investigation provides insight into the conjugated polymer solution process parameters that impact polymer ordering and aggregation in solution and resultant thin films for high-performance organic electronic devices.

In Situ Analysis of Solvent and Additive Effects on Film Morphology Evolution in Spin‐Cast Small‐Molecule and Polymer Photovoltaic Materials

“…There are extensive analyses available in the literature for correlating crystalline morphology characteristics with electronic device performance for P3HT, [73][74][75][76][77][78] PTB7, [20,42,46,[79][80][81][82] DTS, [33,[83][84][85][86][87] and many other materials. To achieve a desired performance gain, these guidelines must then be paired with the appropriate understanding of the relationship between crystalline morphology and device performance in the specific material examined.…”

Enhanced miscibility and strain resistance of blended elastomer/π‐conjugated polymer composites through side chain functionalization towards stretchable electronics

“…Insight into the packing structure of P3Br x HT can be extracted from the ratio of the 0–0 and 0–1 peak transitions ( A 0‐0 / A 0‐1 ) and is a key piece for elucidating functionalization effects on the backbone arrangement because a larger ratio is tied to improved electrical performance . All absorbance spectra of the films exhibited the H‐aggregate character with A 0‐0 / A 0‐1 < 1 indicating greater interchain interactions by π–π stacking, whereas J‐aggregate character with A 0‐0 / A 0‐1 > 1 would be attributed to dominant intrachain interactions by planar, long‐range order (Table ) .…”

Diketopyrrolopyrrole‐based polymer fibrils formation by changing molecular conformation during film formation

“…The relative intensity of 0‐0/0–1 was increased from 0.98 to 1.78 by adding DIO. The higher intensity of 0‐0/0–1 by adding DIO indicated the longer effective conjugation length . To investigate the origin of improving conjugation length by adding DIO, we prepared the samples with CN.…”