Tetracyanobutadiene Bridged Push-Pull Chromophores: Development of New Generation Optoelectronic Materials

This review describes the design strategies used for the synthesis of various tetracyanobutadiene bridged donor-acceptor molecular architectures by a click type [2+2] cycloaddition-retroelectrocyclization (CA-RE) reaction sequence. The photophysical and electrochemical properties of the tetracyanobutadiene bridged molecular architectures based on various moieties including diketopyrrolopyrrole, isoindigo, benzothiadiazole, pyrene, pyrazabole, truxene, boron dipyrromethene (BODIPY), phenothiazine, triphenylamine, thiazole and bisthiazole are summarized. Further, we discuss some important applications of the tetracyanobutadiene bridged derivatives in dye sensitized solar cells, bulk heterojunction solar cells and photothermal cancer therapy.

Molecular structure, IR, Raman and UV-VIS spectra of 2-cyanothiophene and 3-cyanothiophene: A comparative quantum chemical investigation

Spectroscopic data which are needed for detection of new species in the interstellar medium (ISM) are missing for five- and six-membered ring substituted derivatives. In order to supplement the existing literature information, quantum chemical calculations, including geometrical optimizations, simulated IR, Raman and UV-VIS spectra were carried out for 2-cyanothiophene (2CNT) and 3-cyanothiophene (3CNT). Structures for these molecular species were calculated from M06-2X/6-31G(d,p) computed results in conjunction with corrections for systematic deficiencies of basis sets and empirical adjustments for some geometrical parameters. A complete description of IR and Raman spectra including IR frequency assignment and potential energy distribution (PED) analysis is provided. IR and Raman spectra for deuterated species and UV-VIS spectra for thiophene, 2CNT and 3CNT were analyzed. The present computed molecular data are expected to assist astro-scientists in the search of these species in the ISM.

Metal Functionalized Diketopyrrolopyrroles: A Promising Class of Materials for Optoelectronic Applications

After first report on diketopyrrolopyrrole in 1974 by Farnum et al., a wide variety of its derivatives have been reported for material and biological applications. In this review we discuss various design strategies used for the synthesis of metal functionalized diketopyrrolopyrrole derivatives along with their photophysical and electrochemical studies with respect to material and biological applications. Some exciting applications of ferrocenyl functionalized diketopyrrolopyrrole derivatives such as non-linear optics, organic solar cells and photothermal therapy were recently reported, which are also discussed in this review.

Simple and Versatile Non-Fullerene Acceptor Based on Benzothiadiazole and Rhodanine for Organic Solar Cells

Most non-fullerene acceptors (NFAs) are designed in a complex planar molecular conformation containing fused aromatic rings in high-efficiency organic solar cells (OSCs). To obtain the final molecules, however, numerous synthetic steps are necessary. In this work, a novel simple-structured NFA containing alkoxy-substituted benzothiadiazole and a rhodanine end group (BTDT2R) is designed and synthesized. We also investigate the photovoltaic properties of BTDT2R-based OSCs employing representative polymer donors (wide band gap and high-crystalline P3HT, medium band gap and semicrystalline PPDT2FBT, and narrow band gap and low-crystalline PTB7-Th) to compare the performance capabilities of fullerene acceptor-based OSCs, which are well matched with various polymer donors. OSCs based on P3HT:BTDT2R, PPDT2FBT:BTDT2R, and PTB7-Th:BTDT2R achieved efficiency as high as 5.09, 6.90, and 8.19%, respectively. Importantly, photoactive films incorporating different forms of optical and molecular ordering characteristics exhibit favorable morphologies by means of solvent vapor annealing. This work suggests that the new n-type organic semiconductor developed here is highly promising as a universal NFA that can be paired with various polymer donors with different optical and crystalline properties.

Revisiting the Optimal Nano-Morphology: Towards Amorphous Organic Photovoltaics

Organic photovoltaic cells commonly use an active layer with a polycrystalline bulk heterojunction. However, for simplifying the fabrication process, it may be worthwhile to use an amorphous active layer to lessen the burden on processing to achieve optimal performance. While polymers can adopt amorphous phases, molecular glasses, small molecules that can readily form glassy phases and do not crystallize over time, offer an appealing alternative, being monodisperse species. Our group has developed a series of reactive molecular glasses that can be covalently bonded to chromophores to form glass-forming adducts, and this strategy has been used to synthesize glass-forming donor and acceptor materials. Herein, the results of devices incorporating these materials in either partially or fully amorphous active layers are summarized. Additionally, these molecular glasses can be used as ternary components in crystalline systems to enhance efficiency without perturbing the morphology.