title: Ultrahigh mobility in polymer field-effect transistors by design.
abstract: In this article, the design paradigm involving molecular weight, alkyl substituents, and donor-acceptor interaction for the poly[2,6-(4,4-bis-alkyl-4H-cyclopenta[2,1-b;3,4-b']-dithiophene)-alt-4,7-(2,1,3-benzothiadiazole)] (cyclopentadithiophene-benzothiadiazole) donor-acceptor copolymer (CDT-BTZ) toward field-effect transistors (FETs) with ultrahigh mobilities is presented and discussed. It is shown that the molecular weight plays a key role in improving hole mobilities, reaching an exceptionally high value of up to 3.3 cm(2) V(-1) s(-1). Possible explanations for this observation is highlighted in conjunction with thin film morphology and crystallinity. Hereby, it is found that the former does not change, whereas, at the same time, crystallinity improved with ever growing molecular weight. Furthermore, other important structural design factors such as alkyl chain substituents and donor-acceptor interaction between the polymer backbones potentially govern intermolecular stacking distances crucial for charge transport and hence for device performance. In this aspect, for the first time we attempt to shed light onto donor-acceptor interactions between neighboring polymer chains with the help of solid state nuclear magnetic resonance (NMR). On the basis of our results, polymer design principles are inferred that might be of relevance for prospective semiconductors exhibiting hole mobilities even exceeding 3 cm(2) V(-1) s(-1).
authors.affiliation: Max Planck Institute for Polymer Research, Mainz, Germany.
authors.forename: Hoi Nok
authors.initials: HN
authors.lastname: Tsao
authors.forename: Don M
authors.initials: DM
authors.lastname: Cho
authors.forename: Insun
authors.initials: I
authors.lastname: Park
authors.forename: Michael Ryan
authors.initials: MR
authors.lastname: Hansen
authors.forename: Alexey
authors.initials: A
authors.lastname: Mavrinskiy
authors.forename: Do Y
authors.initials: DY
authors.lastname: Yoon
authors.forename: Robert
authors.initials: R
authors.lastname: Graf
authors.forename: Wojciech
authors.initials: W
authors.lastname: Pisula
authors.forename: Hans Wolfgang
authors.initials: HW
authors.lastname: Spiess
authors.forename: Klaus
authors.initials: K
authors.lastname: Müllen