Chloroform outperforms chlorobenzene for enhanced mobility in amphiphilic polymer OFETs

Abstract

High carrier mobility in conjugated polymer-based organic field-effect transistors (OFETs) is often achieved in polymer thin films that display well-ordered long-range structures and good intercrystallite connectivity. While chlorobenzene (CB) is commonly known to yield favorable morphologies for efficient charge transport, in this work, we demonstrate enhanced mobility in the case of chloroform (CF)-processed films over CB. We find that OFETs fabricated from CF exhibit an average mobility of 5.1 × 10⁻³ cm² V⁻¹ s⁻¹, showing nearly a two-fold increase compared to the 2.7 × 10⁻³ cm² V⁻¹ s⁻¹ achieved by the CB protocol. A detailed study of the polymer morphology through UV-vis spectroscopy, GIWAXS, and pMAIRS suggests that large crystallite size and uniform polymer orientation in both crystalline and amorphous domains for CF-processed films led to improved mobility despite the greater local electronic order and lower g-parameter observed in the CB-films. This superior performance observed in CF- over CB-processed films is hypothesized to be due to the amphiphilic nature of the polymer poly(3-hexyl-4′-((2-methoxyethoxy)methyl)-2,2′-bithiophene). Our findings open new avenues for the independent control of electronic order and macroscopic crystallinity through the design of an amphiphilic polymer.