4 research outputs found

    Hetero Bis-Addition of Spiro-Acetalized or Cyclohexanone Ring to 58Ļ€ Fullerene Impacts Solubility and Mobility Balance in Polymer Solar Cells

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    Fullerene bis-adducts are increasingly being studied to gain a high open circuit voltage (<i>V</i><sub>oc</sub>) in bulk heterojunction organic photovoltaics (OPVs). We designed and synthesized homo and hetero bis-adduct [60]Ā­fullerenes by combining fused cyclohexanone or a five-membered spiro-acetalized unit (SAF<sub>5</sub>) with 1,2-dihydromethano (CH<sub>2</sub>), indene, or [6,6]-phenyl-C<sub>61</sub>-butyric acid methyl ester (PCBM). These new eight 56Ļ€ fullerenes showed a rational rise of the lowest unoccupied molecular orbital (LUMO). We perform a systematic study on the electrochemical property, solubility, morphology, and space-charge-limited current (SCLC) mobility. The best power conversion efficiency (PCE) of 4.43% (average, 4.36%) with the <i>V</i><sub>oc</sub> of 0.80 V was obtained for polyĀ­(3-hexylthiophene) (P3HT) blended with SAF<sub>5</sub>/indene hetero bis-adduct, which is a marked advancement in PCE compared to the 0.9% of SAF<sub>5</sub> monoadduct. More importantly, we elucidate an important role of mobility balance between hole and electron that correlates with the device PCEs. Besides, an empirical equation to extrapolate the solubilities of hetero bis-adducts is proposed on the basis of those of counter monoadducts. Our work offers a guide to mitigate barriers for exploring a large number of hetero bis-adduct fullerenes for efficient OPVs

    Facile and Exclusive Formation of Aziridinofullerenes by Acid-catalyzed Denitrogenation of Triazolinofullerenes

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    Variously substituted [6,6]closed aziridinofullerenes were exclusively obtained from acid-catalyzed denitrogenation of triazolinofullerenes without formation of relevant [5,6]open azafulleroids, which are the major products on noncatalyzed denitrogenation. The mechanistic consideration by DFT calculations suggested a reaction sequence involving initial pre-equilibrium protonation of the triazoline N<sub>1</sub> atom, generation of aminofullerenyl cation by nitrogen-extrusion, and final aziridination

    Stereochemistry of Spiro-Acetalized [60]Fullerenes: How the <i>Exo</i> and <i>Endo</i> Stereoisomers Influence Organic Solar Cell Performance

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    Exploiting bis-addition products of fullerenes is a rational way to improve the efficiency of bulk heterojunction-type organic photovoltaic cells (OPV); however, this design inherently produces regio- and stereoisomers that may impair the ultimate performance and fabrication reproducibility. Here, we report unprecedented <i>exo</i> and <i>endo</i> stereoisomers of the spiro-acetalized [60]Ā­fullerene monoadduct with methyl- or phenyl-substituted 1,3-dioxane (<b>SAF</b><sub><b>6</b></sub>). Although there is no chiral carbon in either the reagent or the fullerene, equatorial (<i>eq</i>) rather than axial (<i>ax</i>) isomers are selectively produced at an <i>exo-eq</i>:<i>endo</i>-<i>eq</i> ratio of approximately 1:1 and can be easily separated using silica gel column chromatography. Nuclear Overhauser effect measurements identified the conformations of the straight <i>exo</i> isomer and bent <i>endo</i> isomer. We discuss the origin of stereoselectivity, the anomeric effect, intermolecular ordering in the film state, and the performance of polyĀ­(3-hexylthiophene):substituted <b>SAF</b><sub><b>6</b></sub> OPV devices. Despite their identical optical and electrochemical properties, their solubilities and space-charge limited current mobilities are largely influenced by the stereoisomers, which leads to variation in the OPV efficiency. This study emphasizes the importance of fullerene stereochemistry for understanding the relationship between stereochemical structures and device output

    Highly Ordered <i>n</i>/<i>p</i>ā€‘Co-assembled Materials with Remarkable Charge Mobilities

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    Controlling self-organization and morphology of chemical architectures is an essential challenge in the search for higher energy-conversion efficiencies in a variety of optoelectronic devices. Here, we report a highly ordered donor/acceptor functional material, which has been obtained using the principle of ionic self-assembly. Initially, an electron donor Ļ€-extended tetrathiafulvalene and an electron-acceptor perylene-bisimide were self-organized separately obtaining <i>n</i>- and <i>p</i>-nanofibers at the same scale. These complementary <i>n</i>- and <i>p</i>-nanofibers are endowed with ionic groups with opposite charges on their surfaces. The synergic interactions establish periodic alignments between both nanofibers resulting in a material with alternately segregated donor/acceptor nanodomains. Photoconductivity measurements show values for these <i>n</i>/<i>p</i>-co-assembled materials up to 0.8 cm<sup>2</sup> V<sup>ā€“1</sup> s<sup>ā€“1</sup>, confirming the effectiveness in the design of these heterojunction structures. This easy methodology offers great possibilities to achieve highly ordered <i>n</i>/<i>p</i>-materials for potential applications in different areas such as optoelectonics and photovoltaics
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