Perylenediimide regioisomers with tunable physicochemical and charge-transport properties

Green Synthesis of High-Performance Conjugated Polymers through Optimizing Fused-Ring Structures and Molecular Weights for Organic Field-Effect Transistors

Facile and ecofriendly syntheses are of vital importance to the development of organic semiconductors. Herein, we present a straightforward and green approach for preparing high-performance conjugated polymers. A series of conjugated polymers based on three commercially available multifused rings and benzodifuranedione were designed and synthesized for application in organic field-effect transistors (OFETs). The optical properties, molecular orbital energy levels, and microstructures were systematically investigated. Polymer-based field-effect devices were also fabricated and the electrical properties were optimized by extending the conjugation length, varying the multifused ring structures, and enhancing the molecular weight. The conjugated polymer featuring heptacyclic arenes (dithienothiophen[3,2-b]-pyrrolobenzothiadiazole) achieved a maximum mobility exceeding 1.4 cm2 V-1 s-1 and an Ion/Ioff ratio surpassing 106. This work presents a green aldol synthesis strategy for the preparation of high-performance polymer semiconductor materials.

Asymmetric B←N Functionalized Benzothiadiazoles for High-Performance n-Type Semiconducting Polymers

B←N containing polymers have emerged in organic electronics due to their fascinating optical and electronic properties. Despite these advantages, the development of B←N-based n-type polymers for high-performance organic transistors remains a significant challenge, primarily due to the scarcity of effective B←N containing acceptor units. In this work, we address this challenge through the rational design and synthesis of two asymmetric half-fused B←N functionalized benzothiadiazole derivatives, BTBN and FBTBN. These compounds leverage the unique electronic properties of the B←N motif, enabling the development of two new n-type polymers, PBTBN and PFBTBN. Notably, the lowest unoccupied molecular orbital (LUMO) levels of PBTBN and PFBTBN are significantly lowered by 0.2-0.3 eV compared to their counterparts without B←N functionalization, with PFBTBN achieving a LUMO of ∼ -4.0 eV. Importantly, PFBTBN exhibits exceptional unipolar n-type transistor performance with a high electron mobility (µe) of 3.85 cm2 V-1 s-1. The asymmetric half-fused B←N molecular backbone not only stabilizes the electronic structure but also induces a near-amorphous morphology, thereby enabling PFBTBN-based flexible transistors to retain a high µe of 3.16 cm2 V-1 s-1 even after 1000 bending cycles. This work demonstrates the transformative potential of incorporating asymmetric B←N functionalized acceptors for high-performance n-type semiconducting polymers.

Molecular "backbone surgery" of electron-deficient heteroarenes based on dithienopyrrolobenzothiadiazole: conformation-dependent crystal structures and charge transport properties

Electron-deficient heteroarenes based on dithienopyrrolobenzothiadiazole (BTP) have been highly attractive due to their fascinating packing structures, broad absorption profiles, and promising applications in non-fullerene organic solar cells. However, the control of their crystal structures for superior charge transport still faces big challenges. Herein, a conformation engineering strategy is proposed to rationally manipulate the single crystal structure of BTP-series heteroarenes. The parent molecule BTPO-c has a 3D network crystal structure, which originates from its banana-shaped conformation. Subtracting one thiophene moiety from the central backbone leads to a looser brickwork crystal structure of the derivative BTPO-z because of its interrupted angular-shaped conformation. Further subtracting two thiophene moieties results in the derivative BTPO-l with a compact 2D-brickwork crystal structure due to its quasi-linear conformation with a unique dimer packing structure and short π-π stacking distance (3.30 Å). Further investigation of charge-transport properties via single-crystal organic transistors demonstrates that the compact 2D-brickwork crystal structure of BTPO-l leads to an excellent electron mobility of 3.5 cm2 V-1 s-1, much higher than that of BTPO-c with a 3D network (1.9 cm2 V-1 s-1) and BTPO-z with a looser brickwork structure (0.6 cm2 V-1 s-1). Notably, this study presents, for the first time, an elegant demonstration of the tunable single crystal structures of electron-deficient heteroarenes for efficient organic electronics.

Design of Novel Functional Conductive Structures and Preparation of High-Hole-Mobility Polymer Transistors by Green Synthesis Using Acceptor-Donor-Acceptor Strategies

The design of novel acceptor molecular structures based on classical building blocks is regarded as one of the efficient ways to explore the application of organic conjugated materials in conductivity and electronics. Here, a novel acceptor moiety, thiophene-vinyl-diketopyrrolopyrrole (TVDPP), was envisioned and prepared with a longer conjugation length and a more rigid structure than thiophene-diketopyrrolopyrrole (TDPP). The brominated TVDPP can be sequentially bonded to trimethyltin-containing benzo[c][1,2,5]thiadiazole units via Suzuki polycondensation to efficiently prepare the polymer PTVDPP-BSz, which features high molecular weight and excellent thermal stability. The polymerization process takes only 24 h and eliminates the need for chlorinated organic solvents or toxic tin-based reagents. Density functional theory (DFT) simulations and film morphology analyses verify the planarity and high crystallinity of the material, respectively, which facilitates the achievement of high carrier mobility. Conductivity measurements of the polymeric material in the organic transistor device show a hole mobility of 0.34 cm2 V-1 s-1, which illustrates its potential for functionalized semiconductor applications.