Phase segregation mechanisms of small molecule-polymer blends unraveled by varying polymer chain architecture

Jihua Chen, Sanjib Das, Ming Shao, Guoliang Li, Huada Lian, Jian Qin, James F. Browning, Jong K. Keum, David Uhrig, Gong Gu, Kai Xiao

Research output: Contribution to journalArticlepeer-review

22 Scopus citations

Abstract

As phase separation between the small-molecule semiconductor and the polymer binder is the key enabler of blend-based organic field-effect transistors (OFETs) fabricated by low-cost solution processing, it is crucial to understand the underlying phase separation mechanisms that determine the phase morphology, which significantly impacts device performance. Beyond the parameter space investigated in previous work, here we investigate the formation of blends by varying the branch architecture of the polymer binder and by shortening the solvent dry time using ultrasonic spray casting. The phase morphologies of the resulting blend films have been thoroughly characterized with a variety of techniques in three dimensions over multiple length scales, including AFM, energy-filtered transmission electron microscope, and neutron reflectivity, and have been correlated with electrical transport performance. From the results, we have inferred that the phase morphology is kinetically determined, limited by the inherent slow movement of polymer macromolecules. The kinetic picture, supported by molecular dynamics modeling, not only consistently explains our observations but also resolves inconsistencies in previous works. The achieved mechanistic understanding will guide further optimization of blend-based organic electronics, such as OFETs and organic photovoltaics.

Original languageEnglish
Pages (from-to)367-377
Number of pages11
JournalSmartMat
Volume2
Issue number3
DOIs
StatePublished - Sep 2021

Funding

This research was conducted at the Center for Nanophase Materials Sciences and Spallation Neutron Source, Oak Ridge National Laboratory, which is DOE Office of Science User Facilities.

FundersFunder number
Oak Ridge National Laboratory

    Keywords

    • neutron reflectivity
    • organic field-effect transistors
    • phase separation
    • polymer binders

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