A fullerene bisadduct can enhance the efficiency of polymer:fullerene bulk heterojunction solar cells. The bisadduct has a LUMO that is 100 meV higher compared to that of [6,6]‐phenyl C61 butyric acid methyl ester (PCBM). This increases the open‐circuit voltage of polymer:fullerene bulk heterojunction solar cells based on poly(3‐hexylthio phene) and bisadduct PCBM to 0.73 V, while maintaining high fill factors and currents.

Effect of traps on the performance of bulk heterojunction organic solar cells Mandoc, M. M.; Kooistra, F. B.; Hummelen, J. C.; de Boer, B.; Blom, P. W. M.

We report the synthesis, characterization, and electrochemical properties of ten new fullerene derivatives for usage in organic solar cells. The phenyl ring of PCBM was substituted with electron-donating and electron-withdrawing substituents to study their influence on the LUMO level of the parent fullerene. We varied the LUMO level over a range of 86 mV and show a small but significant change of the open circuit voltage upon application in MDMO-PPV:methanofullerene bulk-heterojunction photovoltaic cells. [structure: see text].

A solution‐processed polymer tandem cell fabricated by stacking two single cells in series is demonstrated. The two bulk‐heterojunction subcells have complementary absorption maxima at λmax ∼ 850 nm and λmax ∼ 550 nm, respectively. A composite middle electrode is applied that serves both as a charge‐recombination center and as a protecting layer for the first cell during spin‐coating of the second cell. The subcells are electronically coupled in series, which leads to a high open‐circuit voltage of 1.4 V, equal to the sum of each subcell. The layer thickness of the first (bottom) cell is tuned to maximize the optical absorption of the second (top) cell. The performance of the tandem cell is presently limited by the relatively low photocurrent generation in the small‐bandgap polymer of the top cell. The combination of our tandem architecture with more efficient small‐bandgap materials will enable the realization of highly efficient organic solar cells in the near future.

We report here the synthesis and characteristics of a new C 84 adduct ([84]PCBM), realized via a diazoalkane addition reaction. [84]PCBM was obtained as a mixture containing three major isomers.[84]PCBM was tested in a fullerene/poly(2-methoxy-5-(3′,7′-dimethyloctyloxy)-p-phenylene vinylene) (MDMO-PPV) bulk heterojunction solar cell as the first C 84 derivative to be applied in device fabrication. Spin coating the active layer blend from 1-chloronaphthalene (the very best fullerene solvent) instead of ortho-dichlorobenzene was necessary to obtain the more efficient photovoltaic device. The PV results indicate that the hole mobility of MDMO-PPV may not be increased upon blending with [84]PCBM. This explains the relatively low I SC of the device as due to the buildup of space charge. The V OC of the device is ∼500 mV lower than that of the one with [60]PCBM, while [84]PCBM has a 350 mV higher electron affinity than [60]PCBM. This loss surpasses the linear relation between the donor HOMOacceptor LUMO energy gap and the V OC in this type of device. A maximum power conversion efficiency of 0.25% was reached for the MDMO-PPV:[84]PCBM cells.

Low-voltage organic transistors based on solution processed semiconductors and selfassembled monolayer gate dielectrics Woebkenberg, Paul H.; Ball, James; Kooistra, Floris B.; Hummelen, Jan C.; de Leeuw, Dago M.; Bradley, Donal D. C.; Anthopoulos, Thomas D. Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Reduction in the operating voltage of organic transistors is of high importance for successful implementation in low-power electronic applications. Here we report on low-voltage n-channel transistors fabricated employing a combination of soluble organic semiconductors and a self-assembled gate dielectric. The high geometric capacitance of the nanodielectric allows transistor operation below 2 V. Solution processing is enabled by analysis of the surface energy compatibility of the dielectric and semiconductor solutions. Electron mobilities in the range of 0.01-0.04 cm 2 / V s and threshold voltages ഛ0.35 V are demonstrated. The present work paves the way toward solution processable low-voltage/power, organic complementary circuits.

Air‐stable n‐channel organic transistors are fabricated using a newly synthesized soluble fullerene derivative. The air‐stable nature of this molecule allows the realization of complementary circuits under ambient conditions without encapsulation. As shown in the figure, the I–V characteristics of the devices are retained even after exposure to air for a week. To the best of our knowledge, this is the first demonstration of an air‐stable electron‐transporting fullerene‐based molecule.

Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. The dissociation efficiency of bound electron-hole pairs at the donor-acceptor interface in bulk heterojunction solar cells is partly limited due to the low dielectric constant of the polymer:fullerene blend. We investigate the photocurrent generation in blends consisting of a fullerene derivative and an oligo͑oxyethylene͒ substituted poly͑p-phenylene vinylene͒ ͑PPV͒ derivative with an enhanced relative permittivity of 4. It is demonstrated that in spite of the relatively low hole mobility of the glycol substituted PPV the increase in the spatially averaged permittivity leads to an enhanced charge dissociation of 72% for these polymer:fullerene blends.