Half‐Fused Diketopyrrolopyrrole‐Based Conjugated Donor–Acceptor Polymer for Ambipolar Field‐Effect Transistors

Abstract

IntroductionConjugated donor-acceptor (D-A) polymers have attracted increasing attention due to their easily modified structures, good solution rheology, semiconducting properties, and A novel building block, denoted as half-fused diketopyrrolopyrrole (DPP) (9-(3-octadecylhenicosyl)-8-(thiophen-2-yl)-7H-pyrrolo[3,4-a]thieno[3,2-g] indolizine-7,10(9H)-dione), in which one of the flanking thiophene units is fused to one of the DPP rings via a carbon-carbon double bond at the N-position is reported. The half-fused DPP is successfully utilized as an electron acceptor to prepare the conjugated donor-acceptor polymer PTFDFT, which exhibits ambipolar semiconducting behavior in ambient air. Theoretical calculations and absorption spectral studies show that the backbone of PTFDFT is more planar compared to the reference polymer with conventional DPP units. As a result, PTFDFT shows a narrow bandgap and low lowest unoccupied molecular orbital level. The more planar backbone with fewer side chains favors the dense packing of the polymer chains of PTFDFT with a short π-π stacking distance (3.49 Å). Grazing-incidence wide-angle X-ray scattering data further confirm the predominant edge-on packing mode of the PTFDFT polymer chains on the substrate. As expected, the PTFDFT thin film shows excellent ambipolar semiconducting properties under ambient conditions, reaching 2.23 and 1.08 cm 2 V −1 s −1 for the n-and p-channels, respectively. In addition, complementary-like inverter with gain value as high as 141 is successfully constructed using the PTFDFT thin film. mechanical properties. [1][2][3] Accordingly, they show promising applications in largearea, lightweight, and flexible electronic devices. [4,5] Among them, ambipolar conjugated D-A polymers, which are capable of transporting both electron and hole carriers, have drawn interest due to the fact that they facilitate the fabrication of complementary-like logic circuits using singlecomponent solution processing instead of selective deposition of p-and n-channel materials, which demand advanced patterning techniques. [6] In the pursuit of high ambipolar performance polymeric field-effect transistors (FETs), various conjugated D-A polymers have been developed and investigated. Different electron acceptors, including diketopyrrolopyrrole (DPP), [2e,7,8] isoindigo, [9] and naphthalene diimide, [10] have been introduced into conjugated D-A polymers to obtain ambipolar semiconductors. [2e,6-11] Among them, DPP-based polymers have been intensively investigated as semiconducting materials for FETs. [2e,6b,7,8,12,13] However, a large number of DPP-based polymers mainly show hole mobilities. This is because of the hindrance of electron injection due to the large gaps between lowest unoccupied molecular orbitals (LUMOs) (−3.2 to −3.6 eV) of DPP-based polymers and the electrode (normally gold) W F (work function ≈ 5.1 eV), while their highest occupied molecular orbitals (HOMOs) (−5.0 to −5.5 eV) were close to the W F of gold. [12] Therefore, lowering the LUMOs of DPP-based conjuga...

Benzo/Naphthodifuranone‐Based Polymers: Effect of Perpendicular‐Extended Main Chain π‐Conjugation on Organic Field‐Effect Transistor Performances

“…[ 15,16 ] Therefore, numerous strategies of tailoring the backbone structures of CPs such as quinoidalization, ladderization, incorporation of non‐covalent interactions, or simply π‐extension of the building blocks within main chains have been applied for the ultimate purpose of delivering high performances in different organic electronic devices. [ 17–20 ]…”

“…Compared to BDF, the NDF structure bears an additional phenyl ring fused onto the quinoidal core ( Figure ), thus resulting in a perpendicular π‐extended conjugated main chain of the NDF‐based polymers, which should potentially be beneficial for providing more intermolecular π‐stacking and interactions for efficient charge transport. [ 19 ] On the other hand, due to the existed steric hindrance between the two flanked phenyl rings and the central core of NDF, the lower backbone coplanarity of NDF‐based polymer might be detrimental to the intramolecular charge transport of the materials in the OFET devices. [ 32,33 ] Therefore, the two polymers provide an ideal platform for investigating the effect of perpendicular π‐extension in the polymer main chains on their physicochemical properties and charge transport behaviors.…”

Selenophene‐Flanked Diketopyrrolopyrrole Based Conjugated Polymers for Ambipolar Field‐Effect Transistors

“…The half‐fused SeDPP monomer 5 was obtained by intramolecular Friedel‐Crafts reaction of 4 in 63% yield. [ 5e,11 ] Finally, PSeDPPFT and PSeFDFT were obtained via the respective Stille coupling of SeDPP 3 and half‐fused SeDPP 5 and bis‐stannylated difluorothiophene in 93% and 98% yields, respectively. The number‐averaged molecular weights of PSeDPPFT and PSeFDFT were measured and found to be 26.5 and 33.3 kDa with polydispersities ( Ð ) of 1.2 and 1.7, respectively, using high temperature gel permeation chromatography.…”

Recent structural evolution of lactam- and imide-functionalized polymers applied in organic field-effect transistors and organic solar cells

“…Recently, P55 was reported based on a novel building block, half-fused DPP, with one of the lactam nitrogen atoms embedded in a six-membered ring fused with the adjacent thiophene anking unit. 76 Besides the much more red-shied absorption relative to the DPP-counterpart, the more rigid backbone and decreased steric hindrance provided the P55 lm with more ordered lamellar packing and denser p-p stacking, with the distances of 28.5 and 3.45Å, respectively (Fig. 6a).…”