Unraveling the Co‐Crystallization–Charge Transport Relation in Conjugated Polymer Blends via Meniscus‐Assisted Solution‐Shearing

Abstract

The ability to craft the co‐crystallization in conjugated polymer blends represents an important endeavor for the enhancement of charge transport. However, simple and efficient approaches to co‐crystallization have yet to be realized. Herein, for the first time, a robust meniscus‐assisted solution‐shearing (MASS) strategy is reported to achieve co‐crystallization in the poly(2,5‐bis(3‐hexylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT‐C6) and poly(2,5‐bis(3‐decylthiophen‐2‐yl)thieno[3,2‐b]thiophene) (PBTTT‐C10) blended films, and correlate this co‐crystalline structure to the charge transport properties. The as‐cast PBTTT‐C6/PBTTT‐C10 blends exhibit co‐crystalline or phase‐separated structures influenced by their molecular weights. Interestingly, confined‐shearing of the initial phase‐separated blended solution to MASS produces the formation of their co‐crystallization. The co‐crystallization kinetics accompanied by the chain packing change and optical properties are scrutinized. Finally, the resulting organic field‐effect transistors (OFETs) signify the cocrystal‐facilitated charge transport in the blends. Conceptually, this efficient MASS strategy in rendering the co‐crystallization in conjugated polymer blends can be readily extended to other conjugated polymer blends of interest for a variety of device applications.

Employment of Alkoxy Sidechains in Semicrystalline Semiconducting Polymers for Ambient-Stable p-Doped Conjugated Polymers

“…The (100) peaks in PBTTT− (OC20) 2 and PBTTT−i−(OC20) 2 correspond to the d-spacing of 27.8 and 26.4 Å, respectively, which is larger than that of PBTTT−C14 (21.3 Å) by 6.5 and 5.1 Å, respectively. The former could be reasonable for the response to an increase in sidechain length in alkyl PBTTT polymers, which demonstrate interdigitated lamellae, 38,39 whereas the smaller d-spacing in PBTTT−i−(OC20) 2 probably arises from the isomeric sidechain positions. Upon doping, the peak shift in PBTTT−C14 was consistent with the literature.…”

Tailoring Polymorph, Cocrystallization, and Phase Separation in Conjugated Polymer Blends via Meniscus-Assisted Solution Shearing

“…To date, several effective dry processing strategies, including thermal or solvent annealing, , rubbing, and mechanical stretching, have been widely utilized to regulate the thin-film microstructures of conjugated polymers. By contrast, solution shearing, a representative wet processing technique, has recently garnered much attention to nucleate and grow crystal domains. − For example, long-range highly oriented poly­(3-hexylthiophene) nanowires are achieved by blade coating, thereby inducing the charge transport anisotropy . Recently, an acceptor and donor blended film with higher crystallinity and smaller phase separation morphology has been achieved via blade coating, leading to improved power conversion efficiency (PCE) in solar cells .…”