Synergistic Use of All-Acceptor Strategies for the Preparation of an Organic Semiconductor and the Realization of High Electron Transport Properties in Organic Field-Effect Transistors

Organic Transistors Based on Highly Crystalline Donor-Acceptor π-Conjugated Polymer of Pentathiophene and Diketopyrrolopyrrole

Oligomers and polymers consisting of multiple thiophenes are widely used in organic electronics such as organic transistors and sensors because of their strong electron-donating ability. In this study, a solution to the problem of the poor solubility of polythiophene systems was developed. A novel π-conjugated polymer material, PDPP-5Th, was synthesized by adding the electron acceptor unit, DPP, to the polythiophene system with a long alkyl side chain, which facilitated the solution processing of the material for the preparation of devices. Meanwhile, the presence of the multicarbonyl groups within the DPP molecule facilitated donor-acceptor interactions in the internal chain, which further improved the hole-transport properties of the polythiophene-based material. The weak forces present within the molecules that promoted structural coplanarity were analyzed using theoretical simulations. Furthermore, the grazing incidence wide-angle X-ray scanning (GIWAXS) results indicated that PDPP-5Th features high crystallinity, which is favorable for efficient carrier migration within and between polymer chains. The material showed hole transport properties as high as 0.44 cm2 V-1 s-1 in conductivity testing. Our investigations demonstrate the great potential of this polymer material in the field of optoelectronics.

Novel Divinyl-Flanked Diketopyrrolopyrrole Polymer, Based on a Dimerization Strategy for High-Performance Organic Field-Effect Transistors

In this communication, we report a novel acceptor structural unit, TVDPP, that can be distinguished from classical materials based on TDPP structures. By designing a synthetic route via retrosynthetic analysis, we successfully prepared this monomer and further prepared polymer P2TVDPP with high yield using a Stille-coupling polymerization reaction. The polymer showed several expected properties, such as high molecular weight, thermal stability, full planarity, small π-π stacking distance, smooth interface, and so on. The absorption spectra and energy levels of the polymer were characterized via photochemical and electrochemical analysis. The organic field-effect transistor (OFET), which is based on P2TVDPP, exhibited excellent carrier mobility and an on/off current ratio of 0.41 cm2 V-1 s-1 and ~107, respectively, which is an important step in expanding the significance of DPP-based materials in the field of optoelectronic devices and organic electronics.

Preparation of Novel Organic Polymer Semiconductor and Its Properties in Transistors through Collaborative Theoretical and Experimental Approaches

Conjugated polymer semiconductors based on donor-acceptor structures are commonly employed as core materials for optoelectronic devices in the field of organic electronics. In this study, we designed and synthesized a novel acceptor unit thiophene-vinyl-diketopyrrolopyrrole, named TVDPP, based on a four-step organic synthesis procedure. Stille coupling reactions were applied with high yields of polymerization of TVDPP with fluorinated thiophene (FT) monomer. The molecular weight and thermal stability of the polymers were tested and showed high molecular weight and good thermal stability. Theoretical simulation calculations and 2D grazing-incidence wide-angle X-ray scattering (GIWAXS) tests verified the planarity of the material and excellent stacking properties, which are favorable for achieving high carrier mobility. Measurements based on the polymer as an organic thin film transistor (OTFT) device were carried out, and the mobility and on/off current ratio reached 0.383 cm2 V-1 s-1 and 104, respectively, showing its great potential in organic optoelectronics.

Tuning the Photophysical Properties of Acceptor-Donor-Acceptor Di-2-(2-oxindolin-3-ylidene) Malononitrile Materials via Extended π-Conjugation: A Joint Experimental and Theoretical Study

Many optoelectronic applications require organic semiconductor (OSC) materials with high electron affinity. In this work, a series of novel acceptor-donor-acceptor (A-D-A) materials with low-lying LUMO energy levels were designed and characterized. In this strategy, two acceptor dyes, bis-isatin and di-2-(2-oxindolin-3-ylidene) malononitrile, were connected by various π-bridges (benzene ring, benzo[c][1,2,5]thiadiazole, monothiophene, trithiophene). We varied the length of the π-conjugation of the central core and the linkage position of the acceptor core (4- vs. 6-position of the phenyl ring) to investigate the effect on the optical and electrochemical properties of the materials. We performed density functional theory (DFT) and time-dependent DFT (TD-DFT) studies to gain insight into the dyes' electronic properties by determining the energy levels. Our findings demonstrate that with increasing acceptor strength and π-conjugation length of the core, the wavelength of the longest absorption maximum as well as their respective extinction coefficients are enhanced, which results in band-gap reduction either by lowering the LUMO and/or raising the HOMO energy level of the molecules. The potential practical utility of these materials as electron-transport materials for perovskite solar cells (PSCs) has been demonstrated.

Rational Design of Novel Conjugated Terpolymers Based on Diketopyrrolopyrrole and Their Applications to Organic Thin-Film Transistors

Organic polymer semiconductor materials, due to their good chemical modifiability, can be easily tuned by rational molecular structure design to modulate their material properties, which, in turn, affects the device performance. Here, we designed and synthesized a series of materials based on terpolymer structures and applied them to organic thin-film transistor (OTFT) device applications. The four polymers, obtained by polymerization of three monomers relying on the Stille coupling reaction, shared comparable molecular weights, with the main structural difference being the ratio of the thiazole component to the fluorinated thiophene (Tz/FS). The conjugated polymers exhibited similar energy levels and thermal stability; however, their photochemical and crystalline properties were distinctly different, leading to significantly varied mobility behavior. Materials with a Tz/FS ratio of 50:50 showed the highest electron mobility, up to 0.69 cm2 V-1 s-1. Our investigation reveals the fundamental relationship between the structure and properties of materials and provides a basis for the design of semiconductor materials with higher carrier mobility.

Donor-Acceptor-Based Organic Polymer Semiconductor Materials to Achieve High Hole Mobility in Organic Field-Effect Transistors

Organic polymer semiconductor materials are conveniently tuned to energy levels because of their good chemically modifiable properties, thus enhancing their carrier transport capabilities. Here, we have designed and prepared a polymer with a donor-acceptor structure and tested its potential as a p-type material for organic field-effect transistor (OFET) applications using a solution-processing method. The conjugated polymers, obtained via the polymerization of the two monomers relying on the Stille coupling reaction, possess extremely high molecular weights and thermodynamic stability. Theoretical-based calculations show that PDPP-2S-Se has superior planarity, which is favorable for carrier transport within the main chain. Photophysical and electrochemical measurements systematically investigated the properties of the material and the energy levels with respect to the theoretical values. The maximum hole mobility of the PDPP-2S-Se-based OFET device is 0.59 cm2 V-1 s-1, which makes it a useful material for potential organic electronics applications.