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

Journal Article · · SmartMat
DOI: https://doi.org/10.1002/smm2.1036 · OSTI ID:1805029
ORCiD logo [1]; ORCiD logo [2];  [3];  [2];  [4];  [4]; ORCiD logo [1]; ORCiD logo [1];  [1]; ORCiD logo [5]; ORCiD logo [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States)
  3. Huazhong Univ. of Science and Technology, Wuhan (China)
  4. Stanford Univ., CA (United States)
  5. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
+ Show Author Affiliations

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.

Research Organization:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES). Scientific User Facilities Division
Grant/Contract Number:
AC05-00OR22725
OSTI ID:
1805029
Journal Information:
SmartMat, Journal Name: SmartMat Journal Issue: 1 Vol. 3; ISSN 2688-819X
Publisher:
WileyCopyright Statement
Country of Publication:
United States
Language:
English

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36 MATERIALS SCIENCE
neutron reflectivity
organic field‐effect transistors
phase separation
polymer binders