Unraveling two distinct polymorph transition mechanisms in one n-type single crystal for dynamic electronics

Daniel William Davies, Bumjoon Seo, Sang Kyu Park, Stephen B. Shiring, Hyunjoong Chung, Prapti Kafle, Dafei Yuan, Joseph W. Strzalka, Ralph Weber, Xiaozhang Zhu, Brett M. Savoie, Ying Diao

Research output: Contribution to journalArticlepeer-review


Cooperativity is used by living systems to circumvent energetic and entropic barriers to yield highly efficient molecular processes. Cooperative structural transitions involve the concerted displacement of molecules in a crystalline material, as opposed to typical molecule-by-molecule nucleation and growth mechanisms which often break single crystallinity. Cooperative transitions have acquired much attention for low transition barriers, ultrafast kinetics, and structural reversibility. However, cooperative transitions are rare in molecular crystals and their origin is poorly understood. Crystals of 2-dimensional quinoidal terthiophene (2DQTT-o-B), a high-performance n-type organic semiconductor, demonstrate two distinct thermally activated phase transitions following these mechanisms. Here we show reorientation of the alkyl side chains triggers cooperative behavior, tilting the molecules like dominos. Whereas, nucleation and growth transition is coincident with increasing alkyl chain disorder and driven by forming a biradical state. We establish alkyl chain engineering as integral to rationally controlling these polymorphic behaviors for novel electronic applications.

Original languageEnglish (US)
Article number1304
JournalNature communications
Issue number1
StatePublished - Dec 2023

ASJC Scopus subject areas

  • General Chemistry
  • General Biochemistry, Genetics and Molecular Biology
  • General Physics and Astronomy


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