We report experimental evidence for the photopolymerization of C7o films under irradiation with visible or UV fight. The tendency of C7o to dimerize is also confirmed by molecular dynamics calculations which find that the lowest energy dimer configuration contains a four-membered ring between monomers, similar to that calculated for the Ceo dimer or 'bucky dumbeU'. However, the cross section for this phototransformation is found to be considerably smaller than observed for Ceo, and this is attributed to a reduction in the number of reactive double bonds from 30 in Ceo to only 5 in each polar cap of a C7o molecule.

https://science.sciencemag.org/content/sci/259/5097/955.full.pdf

Photoinduced Polymerization of Solid C60 Films

Recent development of nanotechnology has reshaped the landscape of modern science and technology, while in the meantime raised concerns about the adverse effects of nanomaterials on biological systems and the environment. Owing to their mutual interaction, carbon-based nanomaterials readily aggregate and are not considered potential contaminants in the liquid phase. However, when discharged into the environment, the hydrophobicity of nanomaterials can be averted through their interaction with natural organic matter (NOM), a heterogeneous mixture of decomposed animals and plants and a major pollutant carrier in nature. Consequently, mobile NOM-modified nanomaterials may pose a threat to ecological terrestrial species through further physical, chemical, and biological processes. The impact of nanomaterials on high plants has scantly been examined in the current literature. Among the studies available, none have used major food crops or carbon nanoparticles (a major class of nanomaterials) for their evaluations. Although both enhanced and inhibited growth have been reported for vegetations exposed to nanomaterials at various developmental stages, including seed germina-

Uptake, Translocation, and Transmission of Carbon Nanomaterials in Rice Plants

Light-induced structural dynamics plays a vital role in the physical properties, device performance, and stability of hybrid perovskite–based optoelectronic devices. We report that continuous light illumination leads to a uniform lattice expansion in hybrid perovskite thin films, which is critical for obtaining high-efficiency photovoltaic devices. Correlated, in situ structural and device characterizations reveal that light-induced lattice expansion benefits the performances of a mixed-cation pure-halide planar device, boosting the power conversion efficiency from 18.5 to 20.5%. The lattice expansion leads to the relaxation of local lattice strain, which lowers the energetic barriers at the perovskite-contact interfaces, thus improving the open circuit voltage and fill factor. The light-induced lattice expansion did not compromise the stability of these high-efficiency photovoltaic devices under continuous operation at full-spectrum 1-sun (100 milliwatts per square centimeter) illumination for more than 1500 hours.

https://science.sciencemag.org/content/sci/360/6384/67.full.pdf

Light-induced lattice expansion leads to high-efficiency perovskite solar cells

All-polymer solar cells (all-PSCs) consisting of polymer donors (PDs) and polymer acceptors (PAs) have drawn tremendous research interest in recent years. It is due to not only their tunable optical, electrochemical, and structural properties, but also many superior features that are not readily available in conventional polymer-fullerene solar cells (fullerene-PSCs) including long-term stability, synthetic accessibility, and excellent film-forming properties suitable for large-scale manufacturing. Recent breakthroughs in material design and device engineering have driven the power conversion efficiencies (PCEs) of all-PSCs exceeding 11%, which is comparable to the performance of fullerene-PSCs. Furthermore, outstanding mechanical durability and stretchability have been reported for all-PSCs, which make them stand out from the other small molecule-based PSCs as a promising power supplier for wearable electronic devices. This review provides a comprehensive overview of the important work in all-PSCs, in which pertinent examples are deliberately chosen. First, we describe the key components that enabled the recent progresses of all-PSCs including rational design rules for efficient PDs and PAs, blend morphology control, and light harvesting engineering. We also review the recent work on the understanding of the stability of all-PSCs under various external conditions, which highlights the importance of all-PSCs for future implementation and commercialization. Finally, because all-PSCs have not yet achieved their full potential and are still undergoing rapid development, we offer our views on the current challenges and future prospects.

Recent Advances, Design Guidelines, and Prospects of All-Polymer Solar Cells.

The discovery and large-scale synthesis of fullerenes have aroused interdisciplinary interest in these closed-cage molecules1,2,3,4,5,6 C60 can be photopolymerized into a form in which the cages are thought to be linked by cyclic C4 units in a [2 + 2] cycloaddition7, provoking theoretical studies of the C60 dimer8,9,10,11,12,13,14,15, the smallest subunit of such a polymer The C60 dimers C120O (refs 16, 17), C121H2( ref 17) and C120O2(ref 18) have been reported, in which the two C60molecules are linked by, respectively, a furan group, a cyclopentane ring and a cyclobutane ring plus two oxygen bridges; but the simplest dimer, C120linked by a cyclobutane ring alone, has not so far been observed We now report that this dumb-bell-shaped molecule can be synthesized by a solid-state mechanochemical reaction of C60 with potassium cyanide Our X-ray structural analysis shows that the C4 ring connecting the cages is square rather than rectangular—the latter is predicted theoretically8,9,13,14,15 The dimer dissociates cleanly into two C60 molecules on heating or one-electron reduction, but in the gas phase during mass-spectrometric measurements it undergoes successive loss of C2 units, shrinking to even-numbered fullerenes such as C118 and C116 in a sequence similar to that seen for other large fullerenes19,20

/pdf/synthesis-and-x-ray-structure-of-dumb-bell-shaped-c-120-13launlzy5.pdf

Synthesis and X-ray structure of dumb-bell-shaped C 120

Photochemical transformation of C60 and C70 films

We report the first ellipsometric measurement of the fundamental optical constants (n,k) of C60 films deposited on Si(100) and Au overcoated Si(100) substrates. We obtain a highest occupied molecular orbital‐lowest unoccupied molecular orbit (HOMO‐LUMO) gap value of 2.3 eV, slightly larger than the gap values obtained from the x‐ray photoelectron spectroscopy and electron‐energy‐loss spectroscopy experiments. The structure observed in the UV is discussed in terms of single‐electron excitations across the HOMO‐LUMO gap.

Ellipsometric determination of the optical constants of C60 (Buckminsterfullerene) films

Thermal decomposition of polymeric C60

The optical absorption (OA) and photoluminescence (PL) spectra of pristine, oxygen-free ${\mathrm{C}}_{60}$ films in the vicinity of the absorption edge across the highest-occupied-molecular-orbital to lowest-unoccupied-molecular-orbital (HOMO-LUMO) gap are studied to elucidate the nature of these electronic states. Structures observed in both the OA and PL spectra are identified with Herzberg-Teller vibronic coupling of the respective singlet electronic states to intramolecular vibrational modes. Similarities and differences among the PL and OA spectra of ${\mathrm{C}}_{60}$ in solution, solid films, and single crystals are discussed. The larger linewidth of the ${\mathrm{C}}_{60}$ film spectra is attributed to the presence of defects, presumably associated with numerous grain boundaries. Finally, the OA and PL spectra of photopolymerized ${\mathrm{C}}_{60}$ solid films are presented. The features in both the OA and PL spectra are observed to broaden considerably. In addition, two of the OA bands blueshift slightly (400--800 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$) and the PL features downshift by \ensuremath{\sim}330 ${\mathrm{cm}}^{\mathrm{\ensuremath{-}}1}$ upon polymerization. These results are consistent with the intermolecular oligomerization bond disorder and reduced symmetry of the ${\mathrm{C}}_{60}$ shell imposed by the covalent bonds between ${\mathrm{C}}_{60}$ molecules in the polymeric phase.

Ying Wang

Papers

Photochemical transformation of C60 and C70 films

Ellipsometric determination of the optical constants of C60 (Buckminsterfullerene) films

Thermal decomposition of polymeric C60

Optical absorption and photoluminescence in pristine and photopolymerized C 60 solid films

Photo-dimerization kinetics in solid C60 films