Fullerene

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

Morphological and electrical control of fullerene dimerization determines organic photovoltaic stability

Abstract: Fullerene dimerization has been linked to short circuit current (Jsc) losses in organic solar cells comprised of certain polymer–fullerene systems. We investigate several polymer–fullerene systems, which present Jsc loss to varying degrees, in order to determine under which conditions dimerization occurs. By reintroducing dimers into fresh devices, we confirm that the photo-induced dimers are indeed the origin of the Jsc loss. We find that both film morphology and electrical bias affect the photodimerization process and thus the associated loss of Jsc. In plain fullerene films, a higher degree of crystallinity can inhibit the dimerization reaction, as observed by high performance liquid chromatography (HPLC) measurements. In blend films, the amount of dimerization depends on the degree of mixing between polymer and fullerene. For highly mixed systems with very amorphous polymers, no dimerization is observed. In solar cells with pure polymer and fullerene domains, we tune the fullerene morphology from amorphous to crystalline by thermal annealing. Similar to neat fullerene films, we observe improved light stability for devices with crystalline fullerene domains. Changing the operating conditions of the investigated solar cells from Voc to Jsc also significantly reduces the amount of dimerization-related Jsc loss; HPLC analysis of the active layer shows that more dimers are formed if the cell is held at Voc instead of Jsc. The effect of bias on dimerization, as well as a clear correlation between PL quenching and reduced dimerization upon addition of small amounts of an amorphous polymer into PC60BM films, suggests a reaction mechanism via excitons.

Polymer-fullerene miscibility: a metric for screening new materials for high-performance organic solar cells.

Abstract: The improvement of the power conversion efficiency (PCE) of polymer bulk heterojunction (BHJ) solar cells has generally been achieved through synthetic design to control frontier molecular orbital energies and molecular ordering of the electron-donating polymer. An alternate approach to control the PCE of a BHJ is to tune the miscibility of the fullerene and a semiconducting polymer by varying the structure of the fullerene. The miscibility of a series of 1,4-fullerene adducts in the semiconducting polymer, poly(3-hexylselenophene), P3HS, was measured by dynamic secondary ion mass spectrometry using a model bilayer structure. The microstructure of the bilayer was investigated using high-angle annular dark-field scanning transmission microscopy and linked to the polymer-fullerene miscibility. Finally, P3HS:fullerene BHJ solar cells were fabricated from each fullerene derivative, enabling the correlation of the active layer microstructure to the charge collection efficiency and resulting PCE of each system....

100% encapsulation of a hydrogen molecule into an open-cage fullerene derivative and gas-phase generation of H2@C60.

Abstract: By applying high-pressure H2 to a new fullerene derivative, C63NO2SPh2Py (1), having a 13-membered-ring orifice, 100% incorporation of a H2 molecule into the fullerene cage has been achieved for the first time. This result substantiates the theoretical calculations indicating that the energy barrier required for H2 insertion through an orifice in 1 is considerably lower than that for the previously reported derivative with the largest orifice among open-cage fullerenes synthesized thus far. Upon matrix-assisted laser desorption/ionization mass spectroscopy, the removal of organic addends from the fullerene derivative 1 encapsulating H2 and restoration of the pristine C60 cage, which retains approximately one-third of incorporated H2, have been observed.

Formation of Fullerenes in H-containing Planetary Nebulae

Abstract: Hydrogen depleted environments are considered an essential requirement for the formation of fullerenes. The recent detection of C60 and C70 fullerenes in what was interpreted as the hydrogen-poor inner region of a post-final helium shell flash planetary nebula (PN) seemed to confirm this picture. Here, we present strong evidence that challenges the current paradigm regarding fullerene formation, showing that it can take place in circumstellar environments containing hydrogen. We report the simultaneous detection of polycyclic aromatic hydrocarbons (PAHs) and fullerenes toward C-rich and H-containing PNe belonging to environments with very different chemical histories such as our own Galaxy and the Small Magellanic Cloud. We suggest that PAHs and fullerenes may be formed by the photochemical processing of hydrogenated amorphous carbon. These observations suggest that modifications may be needed to our current understanding of the chemistry of large organic molecules as well as the chemical processing in space.