Alternating Copolymers Incorporating Dithienogemolodithiophene for Field-Effect Transistor Applications

Molecular Ordering of Dithieno[2,3-d;2',3'-d]benzo[2,1-b:3,4-b']dithiophenes for Field-Effect Transistors

Four derivatives of dithieno[2,3-d;2',3'-d']benzo[1,2-b;3,4-b']dithiophene (DTmBDT) have been synthesized to investigate the correlation between molecular structure, thin-film organization, and charge-carrier transport. Phenyl or thiophene end-capped derivatives at alpha positions of the outer thiophenes of DTmBDT present vastly different optoelectronic properties in comparison with bay-position alkyl-chain-substituted DTmBDT, which was additionally confirmed by density functional theory simulations. The film morphology of the derivatives strongly depends on alkyl substituents, aromatic end-caps, and substrate temperature. Field-effect transistors based on DTmBDT derivatives with bay-substituted alkyl chains show the best performance within this studied series with a hole mobility up to 0.75 cm²/V s. Attachment of aromatic end-caps disturbs the ordering, limiting the charge-carrier transport. Higher substrate temperature during deposition of the DTmBDT derivatives with aromatic end-caps results in larger domains and improved the transistor mobilities but not beyond the alkylated DTmBDT.

Hybrid conjugated polymers with alternating dithienosilole or dithienogermole and tricoordinate boron units

Hybrid conjugated polymers with alternating dithienosilole or dithienogermole and tricoordinate boron units were prepared, which showed effective D–A interactions.

The Design of Radical Stacks: Nitronyl-Nitroxide-Substituted Heteropentacenes

The first alkyl chain-anchored heteropentacene, dithieno[2,3-d;2',3'-d']benzo-[1,2-b;3,4-b']dithiophene (DTmBDT), mono- or disubstituted with a nitronyl nitroxide group has been prepared through a cross-coupling synthetic procedure of the corresponding dibromo-derivative (Br2-DTmBDT) with a nitronyl nitroxide-2-ide gold(I) complex. The synthesized nitroxides possess high kinetic stability, which allowed us to investigate their structure and thermal, optical, electrochemical, and magnetic properties. Single-crystal X-ray diffraction of both mono- and diradicals revealed that the nitronyl nitroxide group lies almost in the same plane as the nearest side thiophene ring. Such arrangement favors formation of edge-to-edge dimers, which then form close π-stacks surrounded by interdigitating alkyl chains. Before melting, these nitronyl nitroxide radical substituted molecules undergo at least two different phase transitions (PTs): for the monoradical, PTs are reversible, accompanied by hysteresis, and occur near 13 and 83 °C; the diradical upon heating shows a reversible PT with hysteresis in the temperature range 2-11 °C and an irreversible PT near 135 °C. PTs of this type are absent in Br2-DTmBDT. Therefore, the step-by-step substitution of bromine atoms by nitronyl nitroxide groups changes the structural organization of DTmBDT and induces the emergence of PTs. This knowledge may facilitate crystal engineering of π-stacked paramagnets and related molecular spin devices.

Recent Development on Narrow Bandgap Conjugated Polymers for Polymer Solar Cells

There have been exciting developments in the field of polymer solar cells (PSCs) as the potential competitor to the traditional silicon-based solar cells in the past decades. The most successful PSCs are based on the bulk hetero-junction (BHJ) structure, which contains a bicontinuous nanoscale interpenetrating network of a conjugated polymer and a fullerene blend. The power conversion efficiencies (PCEs) of BHJ PSCs have now exceeded 11%. In this review, we present an overview of recent emerging developments of narrow bandgap conjugated polymers for PSCs. We focus on a few important acceptors used in the donor-acceptor type conjugated polymers for highly efficient PSCs. We also reviewed the emerged donor-π-acceptor (D-π-A) side chains polymers. The band-gaps and energy levels as well as the photovoltaic performances of conjugated polymers are discussed.

Marriage of heavy main group elements with π-conjugated materials for optoelectronic applications

This review article summarizes recent progress in the synthesis and optoelectronic properties of conjugated materials containing heavy main group elements from Group 13-16 as integral components. As will be discussed, the introduction of these elements can promote novel phosphorescent behavior and support desirable molecular and polymeric properties such as low optical band gaps and high charge mobilities for photovoltaic and thin film transistor applications.

Dithieno[2,3-d;2′,3′-d]benzo[2,1-b;3,4-b‘]dithiophene: a novel building-block for a planar copolymer

A planar heteroacene building block, dithieno[2,3-d;2′,3′-d′]benzo[1,2-b;3,4-b′]dithiophene (DTmBDT), is reported via a facile synthetic procedure.

Naphthodithiophene-Based Conjugated Polymer with Linear, Planar Backbone Conformation and Strong Intermolecular Packing for Efficient Organic Solar Cells

Two donor-acceptor copolymers, PBDT and PNDT, containing 4,8-bis(2-ethylhexyloxy)benzo[1,2-b:3,4-b']dithiophene (BDT) and 4,9-bis(2-ethylhexyloxy)naphtho[1,2-b:5,6-b']dithiophene (NDT), respectively, as an electron-rich unit and 5,6-difluoro-2,1,3-benzothiadiazole (2FBT) as an electron-deficient unit, were synthesized and compared. The introduction of the NDT core into the conjugated backbone was found to effectively improve both light harvesting and the charge carrier mobility by enhancing chain planarity and backbone linearity; the NDT copolymer has stronger noncovalent interactions and smaller bond angles than those of the BDT-based polymer. Moreover, the introduction of the NDT core brings about a drastic change in the molecular orientation into the face-on motif and results in polymer:PCBM blend films with well-mixed interpenetrating nanofibrillar bulk-heterojunction networks with small-scale phase separation, which produce solar cells with higher short-circuit current density and fill factor values. A conventional optimized device structure containing PNDT:PC71BM was found to exhibit a maximum solar efficiency of 6.35%, an open-circuit voltage of 0.84 V, a short-circuit current density of 11.92 mA cm(-2), and a fill factor of 63.5% with thermal annealing, which demonstrates that the NDT and DT2FBT moieties are a promising electron-donor/acceptor combination for high-performance photovoltaics.

High-performance polymer field-effect transistors fabricated with low-bandgap DPP-based semiconducting materials

New π-conjugated D–A copolymers PDMOTT-n combining a diketopyrrolopyrrole unit and a 3,6-dimethoxythieno[3,2-b]thiophene moiety were synthesized, and their field-effect performances were successfully characterized.

Metal triflate-mediated coupling of allylgermanes with thiols: a facile route to thiogermanes

A novel coupling reaction of thiols with (2-methylallyl)germanes catalyzed by metal triflates has been developed.