Printing 2D Conjugated Polymer Monolayers and Their Distinct Electronic Properties

Abstract

Recently, 2D monolayer films of conjugated polymers have gained increasing attention owing to the preeminence of 2D inorganic films that exhibit unique optoelectronic and mechanical properties compared to their bulk analogs. Despite numerous efforts, crystallization of semiconducting polymers into highly ordered 2D monolayer films still remains challenging. Herein, a dynamic‐template‐assisted meniscus‐guided coating is utilized to fabricate continuous, highly ordered 2D monolayer films of conjugated polymers over a centimeter scale with enhanced backbone π–π stacking. In contrast, monolayer films printed on solid substrates confer upon the 1D fiber networks strong alkyl side‐chain stacking at the expense of backbone packing. From single‐layers to multilayers, the polymer π‐stacks change from edge‐on to bimodal orientation as the film thickness reaches ≈20 nm. Spectroscopic and cyclic voltammetry analysis reveals an abrupt increase in J‐aggregation and absorption coefficient and a decrease in bandgap and highest occupied molecular orbital level until critical thickness, possibly arising from the straightened polymer backbone. This is corroborated by an abrupt increase in hole mobility with film thickness, reaching a maximum of 0.7 cm2 V−1 s−1 near the critical thickness. Finally, fabrication of chemical sensors incorporating polymer films of various thicknesses is demonstrated, and an ultrahigh sensitivity of the ≈7 nm thick ultrathin film (bilayers) to 1 ppb ammonia is shown.

Improving Charge Injection at Gold/Conjugated Polymer Contacts by Polymer Insulator‐Assisted Annealing for Transistors

“…Molybdenum trioxide (MoO 3 ) as a hole transport layer could effectively reduce the contact resistance for holes injection from metal electrode into organic semiconductors. [7,34,35] As shown in Figure S5, Supporting Information, the transistors with a MoO 3 inserted layer (3 nm) show high performance and ideal characteristics for hole transport. Whether the pure conjugated polymer or the blend is used as the active layer, there are no kinks in the transfer curves.…”

Impact of open‐shell loading on mass transport and doping in conjugated radical polymers

“…The peak positions and relative intensities of the lowest energy electronic transition (A 0-0 ) and its higher energy vibronic transition (A 0-1 ) can be used to understand conformational changes of the polymer thin films. According to previous reports, [64][65][66][67] the oscillator strength of the 0-0 transition is transferred to the 0-1 transition when the polymer chain conformation changes from linear to curve. As such, a high A 0-0 /A 0-1 peak intensity ratio would, in general, be representative of a planar polymer chain, and this ratio will decrease as the planarity is lost.…”

When Assembly Meets Processing: Tuning Multiscale Morphology of Printed Conjugated Polymers for Controlled Charge Transport

“…(f) Film morphology and molecular packing of DPP2T-TT monolayers printed on ionic liquid (dynamic template) and PTS-SiO 2 and Plasma SiO 2 (static substrates). Reproduced with permission from ref . Copyright 2020 John Wiley and Sons.…”