Polarity and Air-Stability Transitions in Field-Effect
Transistors Based on Fullerenes with Different Solubilizing Groups
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Abstract
A series of <i>o</i>-xylene
and indene fullerene derivatives with varying frontier molecular orbital
energy levels were utilized for assessing the impact of the number
of solubilizing groups on the electrical performance of fullerene-based
organic-field-effect transistors (OFETs). The charge-carrier polarity
was found to be strongly dependent upon the energy levels of fullerene
derivatives. The <i>o</i>-xylene C<sub>60</sub> monoadduct
(OXCMA) and indene C<sub>60</sub> monoadduct (ICMA) exhibited unipolar <i>n</i>-channel behaviors with high electron mobilities, whereas
the bis- and trisadducts of indene and <i>o</i>-xylene C<sub>60</sub> derivatives showed ambipolar charge transport. The OXCMA
OFETs fabricated by solution shearing and molecular <i>n</i>-type doping showed an electron mobility of up to 2.28 cm<sup>2</sup> V<sup>โ1</sup> s<sup>โ1</sup>, which is one of the
highest electron mobilities obtained from solution-processed fullerene
thin-film devices. Our findings systematically demonstrate the relationship
between the energy level and charge-carrier polarity and provide insight
into molecular design and processing strategies toward high-performance
fullerene-based OFETs