Radically Tunable n-Type Organic Semiconductor via Polymorph Control

Daniel William Davies, Sang Kyu Park, Prapti Kafle, Hyunjoong Chung, Dafei Yuan, Joseph W. Strzalka, Stefan C.B. Mannsfeld, Suyin Grass Wang, Yu Sheng Chen, Danielle L. Gray, Xiaozhang Zhu, Ying Diao

Research output: Contribution to journalArticlepeer-review


Polymorphism has emerged as an important design consideration in organic semiconductors (OSCs). Previously, in many OSCs, even small changes in molecular stacking can cause drastic changes to the optical and electronic properties. However, investigation into n-type semiconductors has significantly lagged behind their p-type counterparts. In this work, we present the prolific polymorphism of 2-dimensional quinoidal terthiophene (2DQTT-o-B) and systematically investigate each of 5 polymorphs, 3 of which have been previously unreported. Grazing incidence X-ray diffraction provided a key method to understanding the structure of each polymorph. Via the polymorphic transitions mapped, we tuned the electron mobility by 5 orders of magnitude, from 5.63 × 10-5 to 0.22 cm2 V-1 s-1. These were accompanied by modifications to the optical properties, namely we observed substantial differences in the refractive index noted by intensity differences under polarized optical microscopy and a large shift in optical band gap from 1.18 eV up to 1.40 eV. Finally, we suggest that changes to these properties may be related to the unique quinoidal to aromatic transition observed in quinoidal molecules.

Original languageEnglish (US)
Pages (from-to)2466-2477
Number of pages12
JournalChemistry of Materials
Issue number7
StatePublished - Apr 13 2021

ASJC Scopus subject areas

  • Chemistry(all)
  • Chemical Engineering(all)
  • Materials Chemistry


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