Unraveling the Solution‐State Supramolecular Structures of Donor–Acceptor Polymers and their Influence on Solid‐State Morphology and Charge‐Transport Properties

Abstract

Polymer self-assembly in solution prior to film fabrication makes solution-state structures critical for their solid-state packing and optoelectronic properties. However, unraveling the solution-state supramolecular structures is challenging, not to mention establishing a clear relationship between the solution-state structure and the charge-transport properties in field-effect transistors. Here, for the first time, it is revealed that the thin-film morphology of a conjugated polymer inherits the features of its solution-state supramolecular structures. A "solution-state supramolecular structure control" strategy is proposed to increase the electron mobility of a benzodifurandione-based oligo(p-phenylene vinylene) (BDOPV)-based polymer. It is shown that the solution-state structures of the BDOPV-based conjugated polymer can be tuned such that it forms a 1D rod-like structure in good solvent and a 2D lamellar structure in poor solvent. By tuning the solution-state structure, films with high crystallinity and good interdomain connectivity are obtained. The electron mobility significantly increases from the original value of 1.8 to 3.2 cm V s . This work demonstrates that "solution-state supramolecular structure" control is critical for understanding and optimization of the thin-film morphology and charge-transport properties of conjugated polymers.

Controlling the Microstructure of Conjugated Polymers in High‐Mobility Monolayer Transistors via the Dissolution Temperature

“…[6a] It has to be emphasized that dissolved polymers will often exist in the form of solution-state supramolecular polymer aggregates. [12] The growth of these dissolved aggregates from a fully molecularly dissolved state has been explained by the disorder-order transition model [13] and multi-level self-assembly processes. [14] For conjugated polymers, the molecularly dissolved state is characterized by a single broad absorption peak in the UV/Vis-NIR absorption spectrum, while upon aggregation, a red-shift is observed due to planarization of the polymer backbone, accompanied by the appearance of vibronic peaks or shoulders.…”

Rigid Coplanar Polymers for Stable n‐Type Polymer Thermoelectrics

“…[13c] No significant change was observed between the solution to thin film states of LPPVs, and may result from their rigid backbones or pre-aggregation behaviors in solution. [19] Compared with LPPV-2, LPPV-1 showed about a3 0nmb athochromic shift both in solution and in solid-state films,suggesting their different aggregation behaviors. [20] Thee nergy levels of LPPVs were estimated by cyclic voltammetry (CV).…”

Quantitative Image Analysis of Fractal‐Like Thin Films of Organic Semiconductors

“…Morphology control is crucial to achieving high‐performance devices and to elucidating the complex structure–charge transport property relationship . Morphology is shown to be highly sensitive to processing conditions, such as printing/coating speed, solvent choices, substrate chemistry and topology, and so on. It has been widely shown that morphological parameters can modulate charge carrier mobility by orders of magnitude.…”