Fullerene

About: Fullerene is a research topic. Over the lifetime, 12723 publications have been published within this topic receiving 359173 citations.

Ultra-stable nanoparticles of CdSe revealed from mass spectrometry

Abstract: Nanoparticles under a few nanometres in size have structures and material functions that differ from the bulk because of their distinct geometrical shapes and strong quantum confinement. These qualities could lead to unique device applications. Our mass spectral analysis of CdSe nanoparticles reveals that (CdSe)(33) and (CdSe)(34) are extremely stable: with a simple solution method, they grow in preference to any other chemical compositions to produce macroscopic quantities. First-principles calculations predict that these are puckered (CdSe)(28)-cages, with four- and six-membered rings based on the highly symmetric octahedral analogues of fullerenes, accommodating either (CdSe)(5) or (CdSe)(6) inside to form a three-dimensional network with essentially heteropolar sp(3)-bonding. This is in accordance with our X-ray and optical analyses. We have found similar mass spectra and atomic structures in CdS, CdTe, ZnS and ZnSe, demonstrating that mass-specified and macroscopically produced nanoparticles, which have been practically limited so far to elemental carbon, can now be extended to a vast variety of compound systems.

Improving device efficiency of polymer/fullerene bulk heterojunction solar cells through enhanced crystallinity and reduced grain boundaries induced by solvent additives.

Abstract: Polymer solar cells based on bulk heterojunction (BHJ) structures, featuring conjugated polymers as donors and fullerene derivatives as acceptors, [ 1 ] are being developed for their potential application in the low-cost fabrication of large-area devices. In recent reports, BHJ solar cells incorporating crystalline or low-bandgap conjugated polymers [ 2 ] and fullerene derivatives have exhibited maximum power conversion effi ciencies (PCEs) of up to 8%. [ 3 ] The morphology [ 4 ] of the active layer in a BHJ solar cell incorporating a polymer/fullerene thin fi lm plays a critical role affecting the device performance; phase-separated domains in the active layer provide not only interfaces for charge separation of photogenerated excitons but also percolation pathways for charge carrier transport to the respective electrodes, critically affecting the device’s PCE. The nanoscale morphology of a polymer/fullerene thin fi lm is greatly affected by (i) the fi lm processing conditions, [ 5 ] (ii) the molar ratio (composition) of the polymer and the fullerene, [ 6 ] and (iii) the nature of the solvent additive (if any). [ 7 ] In particular, BHJ polymer solar cells can exhibit improved device performance after undergoing thermal or solvent annealing or the incorporation of solvent additives, all of which alter the fi lm morphology to a more favorable state relative to that of the as-cast fi lm or the fi lm in the absence of the additive, presumably resulting from (i) self-organization of the polymer units into ordered structures and (ii) appropriate aggregation of fullerene domains to provide percolation networks for charge carrier transport. [ 6 , 8 ] Among these approaches, the addition of solvent additive during the processing of the active layer is the simplest and most effective means of optimizing a BHJ device’s morphology; it infl uences the size of the fullerene domains and enhances the crystallinity of the self-organized polymers by improving the solubility of

NMR characterization of isomers of C 78 , C 82 and C 84 fullerenes

Abstract: FOLLOWING the development of a method for bulk synthesis of C60 and other fullerenes1, the isolation of higher fullerenes ranging from C76 to C96 has been achieved using chromatographic techniques2–5. Whereas C60 and C70 have unique, high-symmetry structures6, theoretical calculations for fullerenes larger than C76 have suggested that each may exist in at least two isomeric forms7. For C84, 24 isomers have been postulated7, and for C96calculations have yielded 196 distinct isomers8. Diederich et al.9 have used liquid chromatography and 13C NMR to identify two isomers of C78, but previous experimental studies of other higher fullerenes2 have produced ambiguous results. Here we use 13C NMR to determine the structures of some principal isomers of C78, C82 and C84. We find a third isomer of C78, which was not reported in ref. 9. Characterization of the structures of these larger fullerenes should provide new understanding of the factors determining the stability of hollow carbon clusters.