The first observation that PBBTPD, a low bandgap, ambipolar conjugated donor-acceptor (DA) polymer based on benzobisthiadiazole (BBT), possesses an open-shell singlet ground state as well as a thermally accessible triplet state is described. Similarly, interesting electronic behavior in semiconducting organic DA oligomers based on BBT is also observed. Theoretical predictions have suggested that such behavior is due to the biradicaloid character of BBT and we provide experimental evidence indicating that these predictions are correct. Furthermore, the open shell character strengthens as the conjugation length increases, as observed in the BBT-based polymer, PBBTPD. We show that this biradicaloid structure is observed in each BBT moiety along the chain and that therefore PBBTPD is in fact a polyradicaloid. This observation will most likely aid in the development of better n-type polymeric acceptors for organic semiconductor applications. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2015, 53, 287–293

We report the first example of a stable pyrenotriazinyl radical, 1,3-diphenyl-1,2,4-pyrenotriazin-4-yl (PyT). Magnetic susceptibility measurements of the radical PyT show a transition from a paramagnetic state to an antiferromagnetic state. The pyrene moiety has a strong influence via ππ interactions in 1D chain stacks that result in the observed magnetic properties. Unexpectedly, the pyrene unit has essentially no effect on the electronic structure of the triazinyl core. Chemical sensing studies on various nitrophenol-based compounds showed that the radical PyT exclusively senses picric acid (PA), as a pH sensor, with a detection limit of 5.0×10⁻⁶ M.

A water/alcohol-soluble small molecule based on the commercially available pigment quinacridone is employed as an electron transport layer in organic photovoltaics. The quinacridone derivative is utilized in solution-processed bulk-heterojunction solar cells to improve primarily the fill factor of the devices, contributing to an upwards of 19% enhancement in the power conversion efficiency relative to the control devices with no electron transport layer. The facile synthesis of the quinacridone derivative coupled with the ease of device fabrication via solution processing provide a simple, yet effective means of improving the performance of existing organic photovoltaic cells.

By understanding the role of DMF as a hydride source via a Pd-catalyzed reaction and switching to CH₃CN solvent, an efficient route for the synthesis of emeraldicene and some new substituted derivatives is reported with potential application in organic electronics. Additionally, the nucleophilic alkylation of emeraldicene 4 a with alkyllithium reagents provides monosubstituted compounds 7 a and 7 b, the latter crystallizing in columnar stacks, with π–π overlap between adjacent molecules in the stack.

New conjugated oligomers, oligo(9,9-didodecylfluorene-bis-sulphurdiimide), consisting of 9,9-didodecylfluorene separated by NSN moieties, are reported. These oligomers are stable purple solids under ambient conditions with absorption covering a broad spectral window in the UV-vis range and a main broad peak centered at 555 nm with onset extending to 700 nm. These oligomers show an obviously longer conjugation length than its dimeric analogue, bis-9,9-didodecyl-fluorene-2-sulfurdiimide that shows a band-edge absorption centered at 484 nm with onset at 590 nm. The dimer and oligomers are soluble in a variety of organic solvents. Moreover, we found that the oligomer with an average repeating-unit number of six could significantly quench the photoluminescence (PL) of poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV) or poly(3-hexylthiophene) (P3HT) in the solid state. More importantly, the composites of this oligomer with P3HT showed a nearly 10-fold enhancement of the photocurrent, compared with that of P3HT itself. In addition, the PL of this oligomer could be quenched by the presence of phenyl-C₆₁-butyric acid methyl ester (PCBM) in toluene. These results suggest the presence of photoinduced charge transfer in composites of these oligomers blended with an electronic partner that either donates or accepts electrons. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2011

An asymmetric twistacene, 1′,4′-diphenyl-naphtho-(2′.3′:1.2)-pyrene-6′-nitro-7′-methyl carboxylate (tetracene 2), was synthesized by using benzyne-trapping chemistry. Its structure, determined by X-ray crystallography, confirmed that this material has a twisted topology with torsion angles as high as 23.8(3)°. Organic light-emitting devices using tetracene 2 as either charge-transporting materials or emitters have been fabricated. The results indicate that this material has bipolar transporting behavior in these devices.