A ladder-type poly(phenyl-co-methacryl silsesquioxane) (PPMSQ) copolymer was developed for use as a gate dielectric in high-performance organic field-effect transistors (OFETs). The ladder-type PPMSQ copolymer was synthesized via the hydrolysis of two types of monomers, methacryloxypropyltrimethoxysilane and phenyltrimethoxysilane, followed by a condensation polymerization. The phenyl groups in one monomer were introduced to enhance the structural ordering of the overlying organic semiconductors, whereas the methacryloxypropyl groups in the other monomer were introduced to cross-link the polymer chains via thermal- or photocuring. The curing process enhanced the electrical strength of the gate dielectric layer due to the formation of a network structure with a reduced free volume. Thermal curing reduced the surface energy of the gate dielectrics, which improved the structural order of the overlying organic semiconductors and promoted the formation of large grains. The ladder-type PPMSQ was used as a gate dielectric to produce benchmark p- and n-channel OFETs based on pentacene and N,N′-dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8), respectively. The resulting OFETs exhibited excellent electrical performances, including a high carrier mobility (0.53 cm2 V–1 s–1 for the p-type pentacene OFET and 0.17 cm2 V–1 s–1 for the n-type PTCDI-C8 OFET) and a high ON/OFF current ratio exceeding 104. The photocured patterned PPMSQ film was successfully used to fabricate complementary OFET-based inverters that yielded high gains. The use of the ladder-type PPMSQ gate dielectrics provides a novel approach to realizing next-generation organic electronics.
We investigated the heterojunction effects of perylene tetracarboxylic diimide (PTCDI) derivatives on the pentacene-based field-effect transistors (FETs). Three PTCDI derivatives with different substituents were deposited onto pentacene layers and served as charge transfer dopants. The deposited PTCDI layer, which had a nominal thickness of a few layers, formed discontinuous patches on the pentacene layers and dramatically enhanced the hole mobility in the pentacene FET. Among the three PTCDI molecules tested, the octyl-substituted PTCDI, PTCDI-C8, provided the most efficient hole-doping characteristics (p-type) relative to the fluorophenyl-substituted PTCDIs, 4-FPEPTC and 2,4-FPEPTC. The organic heterojunction and doping characteristics were systematically investigated using atomic force microscopy, 2D grazing incidence X-ray diffraction studies, and ultraviolet photoelectron spectroscopy. PTCDI-C8, bearing octyl substituents, grew laterally on the pentacene layer (2D growth), whereas 2,4-FPEPTC, with fluorophenyl substituents, underwent 3D growth. The different growth modes resulted in different contact areas and relative orientations between the pentacene and PTCDI molecules, which significantly affected the doping efficiency of the deposited adlayer. The differences between the growth modes and the thin-film microstructures in the different PTCDI patches were attributed to a mismatch between the surface energies of the patches and the underlying pentacene layer. The film-morphology-dependent doping effects observed here offer practical guidelines for achieving more effective charge transfer doping in thin-film transistors.
Zeolites are three-dimensional aluminosilicates having unique properties from the size and connectivity of their sub-nanometer pores, the Si/Al ratio of the anionic framework, and the charge-balancing cations. The inhomogeneous distribution of the cations affects their catalytic performances because it influences the intra-crystalline diffusion rates of the reactants and products. However, the structural deformation regarding inhomogeneous active regions during the catalysis is not yet observed by conventional analytical tools. Here we employ in situ X-ray free electron laser-based time-resolved coherent X-ray diffraction imaging to investigate the internal deformations originating from the inhomogeneous Cu ion distributions in Cu-exchanged ZSM-5 zeolite crystals during the deoxygenation of nitrogen oxides with propene. We show that the interactions between the reactants and the active sites lead to an unusual strain distribution, confirmed by density functional theory simulations. These observations provide insights into the role of structural inhomogeneity in zeolites during catalysis and will assist the future design of zeolites for their applications.
We synthesized a solution-processable low band gap small molecule, Si1TDPP-EE-COC6, for use as a semiconducting channel material in organic thin film transistors (OTFTs). The Si1TDPP-EE-COC6 is composed of electron-rich thiophene−dithienosilole−thiophene (Si1T) units and electron-deficient diketopyrrolopyrrole (DPP) and carbonyl units. SiTDPP-EE-COC6-based OTFTs with Au source/drain electrodes were fabricated, and their electrical properties were systematically investigated with increasing thermal annealing temperature. The hole and electron mobilities of as-spun Si1TDPP-EE-COC6 were 3.3 × 10 −4 and 1.7 × 10 −4 cm 2 V −1 s −1 , respectively. The carrier mobilities increased significantly upon thermal annealing at 150°C, yielding a hole mobility of 0.003 cm 2 V −1 s −1 and an electron mobility of 0.002 cm 2 V −1 s −1 . The performance enhancement upon thermal annealing was strongly associated with the formation of a layered edge-on structure and a reduction in the π−π intermolecular spacing. Importantly, the use of atomically thin single-layer graphene (SLG) source/drain electrodes that were grown by the chemical vapor deposition (CVD) method further increased the carrier mobilities. The 150°C annealed Si1TDPP-EE-COC6-based OTFTs with SLG source/drain electrodes exhibited a hole mobility of 0.011 cm 2 V −1 s −1 and an electron mobility of 0.015 cm 2 V −1 s −1 . The improved electrical performances of the SLG OTFTs were attributed to the stepless flat surface of the SLG electrodes and the better interfacial contact between the Si1TDPP-EE-COC6 molecules and the SLG electrodes compared to the Au electrodes. This work suggests that careful chemical design is essential to enhance balanced ambipolar transistor performance based on small conjugated molecules, and the SLG is a good electrode material to promote the carrier mobilities.
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.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.