Neuromorphic computation possesses the advantages of self-learning, highly parallel computation, and low energy consumption, and is of great promise to overcome the bottleneck of von Neumann computation. In this work, a series of poly(3-hexylthiophene) (P3HT)-based block copolymers (BCPs) with different coil segments, including polystyrene, poly(2-vinylpyridine) (P2VP), poly(2-vinylnaphthalene), and poly(butyl acrylate), are utilized in photosynaptic transistor to emulate paired-pulse facilitation, spike time/rate-dependent plasticity, short/long-term neuroplasticity, and learning−forgetting−relearning processes. P3HT serves as a carrier transport channel and a photogate, while the insulating coils with electrophilic groups are for charge trapping and preservation. Three main factors are unveiled to govern the properties of these P3HT-based BCPs: i) rigidity of the insulating coil, ii) energy levels between the constituent polymers, and iii) electrophilicity of the insulating coil. Accordingly, P3HT-b-P2VP-based photosynaptic transistor with a sought-after BCP combination demonstrates long-term memory behavior with current contrast up to 10 5 , short-term memory behavior with high paired-pulse facilitation ratio of 1.38, and an ultralow energy consumption of 0.56 fJ at an operating voltage of −0.0003 V. As far as it is known, this is the first work to utilize conjugated BCPs in an electret-free photosynaptic transistor showing great potential to the artificial intelligence technology.
The
development of a π-conjugated polymer with hydrogen-bonding
moieties has aroused great attention because of the improved molecular
stacking and the hydrogen-bonding network. In this study, PDPPTVT
(diketopyrrolopyrrole-thiophenevinylenethiophene) and PDPPSe (diketopyrrolopyrrole-selenophene)
alkylated with a carbosilane (SiC8) side chain and poly(acryl amide)
(PAM)-incorporated alkyl side chain were prepared, and their structure–performance
and structure–stretchability correlation were evaluated. By
incorporating the DPPTVT backbone and 0, 5, 10, or 20% PAM-incorporated
alkyl side chain, the μh value could reach 2.0, 0.97,
0.74, and 0.42 cm2 V–1 s–1, respectively (P1 to P4). The polymer
with the PDPPSe backbone and 5% PAM-incorporated alkyl side-chain
(P5) exhibited the maximum μh value
of 0.96 cm2 V–1 s–1. By extending the PAM moiety from the backbone with alkyl spacers,
the solid-state packing and edge-on orientation can be properly maintained.
Surprisingly, the PAM-incorporated alkyl side-chain can provide a
hydrogen-bonding network serving as sacrificial bonding to mechanical
deformation. Therefore, the relevant changes in the crystallographic
parameters including the crystalline size and the in-plane π–π
stacking distance with a 100% external strain were less than 4 and
0.8%, respectively, from P1 to P3. Therefore, P3 achieved an excellent stretchability while maintaining
its molecular orientation and charge-transporting performance. Even
with 100% external strain, P3 still provided an orthogonal
μh over 0.1 cm2 V–1 s–1. Moreover, by substituting the TVT moiety with the
Se moiety, the ductility of the backbone can be further increased
when the elastic modulus decreases from 0.80 to 0.36 GPa for P2 to P5. The achieved high μh retention is over 20% after 500 stretching–releasing cycles
with a 60% external strain perpendicular to the channel direction
for the polymer composed of PDPPSe and 5% PAM content. The results
manifest that our newly designed DPP with the PAM-incorporated alkyl
side chain provides a promising approach to promote the intrinsic
stretchability of the π-conjugated polymers.
Regioregular polythiophenes have been widely used in organic electronic applications due to their solution processability with chemical modification through side chain engineering, as well as their microstructural organization and good hole transport properties. Here, we introduce alkylthio side chains, (poly[(3-alkylthio)thiophene]s; P3ATTs), with strong noncovalent sulfur molecular interactions, to main chain thienyl backbones. These P3ATTs were compared with alkyl-substituted polythiophene (poly(3-alkylthiophene); P3AT) variants such that the effects of straight (hexyl and decyl) and branched (2-ethylhexyl) side chains (with and without S atoms) on their thin-film morphologies and crystalline states could be investigated. P3ATTs with linear alkylthio side chains (P3HTT, hexylthio; P3DTT, decylthio) did not attain the expected higher organic field-effect transistor (OFET) mobilities with respect to P3HT (hexyl) and P3DT (decyl) mainly due to their lower regioregularity (76−78%), although P3ATTs exhibit an enhanced tendency for aggregation and compact molecular packing, as indicated by the red-shifting of the absorption spectra and the shortening of the π−π stacking distance, respectively. Moreover, the loss of regioregularity issue can be solved by introducing more soluble 2-ethylhexylthio branched side chains to form poly [3-(2-ethylhexylthio)thiophene] (P3EHTT), which provides enhanced crystallinity and efficient charge mobility (increased by up to a factor of 3) with respect to the poly(2-ethylhexylthiophene) (P3EHT) without S atoms in the side moieties. This study demonstrates that the presence of side chain alkylthio structural motifs with nonbonded interactions in polythiophene semiconductors has a beneficial impact on the molecular conformation, morphologies, structural packing, and charge transport in OFET devices.
A novel A-b-poly(3-hexylthiophene)(P3HT)-b-C type triblock copolymer was successfully synthesized by the bilateral Cu-catalyzed azide alkyne cycloaddition reaction using α,ω-bifunctionalized P3HT.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.