Hydrogen-Bonding-Facilitated Layer-by-Layer Growth of Ultrathin Organic Semiconducting Films

Abstract

We demonstrated that the layer-by-layer growth of thin film crystals of conjugated organic molecules is facilitated by their hydrogen-bonding capabilities. We synthesized bis(3-hydroxypropyl)-sexithiophene (bHP6T), which includes two hydroxyalkyl groups that promote interlayer and intermolecular molecular interactions during the crystal growth process. Under the optimal deposition conditions, the crystals grew in a nearly perfect layer-by-layer mode on the solid substrate surfaces, enabling the formation of uniform charge transporting films as thin as a few monolayers. A thin film transistor device prepared from a bHP6T film only 9 nm thick exhibited a charge carrier mobility well above 1 × 10(-2) cm(2)/(V s) and an on/off ratio exceeding 1 × 10(4). These properties are better than the properties of other sexithiophene-based devices yet reported. The devices exhibited enhanced stability under atmospheric conditions, and they functioned properly, even after storage for more than 2 months.

Crystallization and Organic Field‐Effect Transistor Performance of a Hydrogen‐Bonded Quaterthiophene

“…The effect of hydrogen‐bonded groups on the charge‐carrier mobility of certain sexithiophenes and naphthalene diimides in OFETs was investigated, but no improvement in device performance was observed. An α,ω‐hydroxypropyl‐substituted sexithiophene was found to exhibit enhanced layer‐by‐layer thin‐film growth and was successfully used in thin‐film devices . Hydrogen bonding has been applied in the solution‐phase self‐assembly of oligothiophene derivatives into one‐dimensional aggregates; but, whereas field‐effect devices have been used, in some cases, to determine the properties of the resulting aggregates, the specific role of hydrogen bonding for macroscopic device performance was not systematically investigated in these studies.…”

Electrochemical synthesis of highly ordered polypyrrole on copper modified aluminium substrates

“…It is widely accepted that the electrical and optical properties of conjugated polymers in thin films are closely related with ordered molecular packing, crystallinity and interchain distance of π-conjugated segments [11]. Studies on orientation and molecular ordering/crystallinity of conjugated polymers such as (poly(3-hexylthiophene) [11], poly(phenylene vinylene) [12], poly(p-phenylene)s [13], bis(3-hydroxypropyl)-sexithiophene [14], etc. have been previously reported, however, the crystallinity of ordered PPy deposited on metal surfaces has not been investigated in-depth in these reports [8].…”

Recent progress in organic photovoltaics: device architecture and optical design

“…Meanwhile, several other groups have designed small molecules with self-complementary intermolecular hydrogen bonding, in an attempt to self-organize the active materials into ordered bulk HJs. [176][177][178][179] These reports all showed a positive impact of the hydrogen bonding, although a clear demonstration of the ordered/interdigitated bulk HJ morphology is still lacking.…”