Optimizing Morphology to Trade Off Charge Transport and Mechanical Properties of Stretchable Conjugated Polymer Films

Abstract

Conjugated polymers are a promising candidate for large-area stretchable electronics because of their tunable electrical and mechanical properties, light weight, and low-cost solution processing. Significant research progress has been achieved in stretchable polymer electronics by synthesizing novel conjugated polymer materials and designing new device geometries. However, the inherent competition between high charge mobility and good mechanical compliance has long existed for conjugated polymer films. In this Perspective, we will provide an understanding of how to balance the electrical properties and mechanical properties from the point of view of multiple length scale microstructures of conjugated polymers. After a brief introduction of microstructure features, charge transport, and mechanical properties in thin films, we focus on how to design the percolation morphology with the aggregates, tie chains, and amorphous phase via controlling solution preaggregation and film-formation dynamics. Furthermore, the rational transfer of film morphology from small-area coating to large-area printing is discussed in terms of film uniformity and crystallization control. Finally, we summarize the challenges and opportunities in microstructure control of stretchable conjugated polymer films.

Unrevealing the interaction between O2 molecules and poly(3-hexylthiophene-2,5-diyl) (P3HT)

“…It is known that conjugated polymers form amorphous and semicrystalline structures when processed to thin lms. [43][44][45] In the ordered regions the charge transport is delocalised whereas it is very localised in the amorphous parts. Thin lm crystallinity is determined by several parameters and depends on many conditions from synthesis to lm processing.…”

Strain-insensitive naphthalene-diimide-based conjugated polymers through sequential regularity control

“…33 CPs with high molecular weights have a high propensity to bridge adjacent crystalline domains, thereby generating tie chains in the thin film. 34 D–A-type CPs with high persistence lengths (ranging from 5–40 nm) show high critical molecular weights to form a percolation network of tie chains within the crystalline and amorphous domains. 35 However, reducing crystallinity and enhancing chain entanglement are favorable for forming a percolation network of tie chains within the crystalline and amorphous domains.…”

Gaining control over conjugated polymer morphology to improve the performance of organic electronics

“…24 Therefore, it is essential to study the microstructure-property relationship and develop strategies to control molecular packing and film morphology. 17 In-depth investigation of CP aggregation, crystallization behaviors, and phase transitions alongside developing new experimental and computational microstructure characterization will help address these limitations.…”

“…1a). 17,33 The intrinsic structural anisotropy and polymer chain defects cause non-coherent charge transport, making measuring and predicting charge mobility challenging. 34 On the contrary, highly ordered regioregular CPs tend to reveal high charge mobility.…”

“…1c). 17,27 In the case of a CP, deformability is governed both by a rigid conjugated backbone and flexible side chains. That results in complex behavior.…”