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Azimi H.,Friedrich - Alexander - University, Erlangen - Nuremberg | Kuhri S.,Friedrich - Alexander - University, Erlangen - Nuremberg | Osvet A.,Friedrich - Alexander - University, Erlangen - Nuremberg | Matt G.,Friedrich - Alexander - University, Erlangen - Nuremberg | And 8 more authors.
Journal of the American Chemical Society | Year: 2014

In colloidal nanoparticle (NPs) devices, trap state densities at their surface exert a profound impact on the rate of charge carrier recombination and, consequently, on the deterioration of the device performance. Here, we report on the successful application of a ligand exchange strategy to effectively passivate the surface of cuprite (Cu2O) NPs. Cu2O NPs were prepared by means of a novel synthetic route based on flame spray pyrolysis. FTIR, XRD, XPS, and HRTEM measurements corroborate the formation of cubic cuprite Cu2O nanocrystals, excluding the possible presence of undesired CuO or Cu phases. Most importantly, steady-state emission and transient absorption assays document that surface passivation results in substantial changes in the intensity of emissive excitonic states-centered at copper and oxygen vacancies-and in the lifetime of excitons near the band edge. To shed light onto ultrafast processes in Cu2O nanocrystals additional pump probe experiments on the femtosecond and nanosecond time scales were carried out. Two discernible species were observed: on one hand, an ultrafast component (∼ps) that relates to the excitons; on the other hand, a long-lived component (∼μs) that originates from the defects/trap states. © 2014 American Chemical Society.

Schumacher C.M.,Institute for Chemical and Bioengineering | Loepfe M.,Institute for Chemical and Bioengineering | Fuhrer R.,Nanograde Ltd. | Grass R.N.,Institute for Chemical and Bioengineering | Stark W.J.,Institute for Chemical and Bioengineering
RSC Advances | Year: 2014

We present a gas combustion powered soft pump made from highly durable and flexible polydimethylsiloxane (soft silicone). Our soft pump was able to run for 10000 combustion cycles at a constant combustion power rating of 500 watts and thus discloses novel prospects for long-lasting soft-machines at high specific energy-densities. This journal is © the Partner Organisations 2014.

Walser T.,ETH Zurich | Hellweg S.,ETH Zurich | Juraske R.,ETH Zurich | Luechinger N.A.,Nanograde Ltd. | And 3 more authors.
Science of the Total Environment | Year: 2012

In the life cycle of engineered nanoparticles (ENP), their manufacturing requires particular attention because of unwanted potential ENP emissions to workplaces. We simulated three scenarios of equipment failure during gas phase production of nanoparticles in a laboratory. The emission plume of nanoparticles was tracked with high spatial and temporal resolution by 10 measurement devices. While under normal production conditions, no elevated ENP concentrations were observed, worst case scenarios led to homogeneous indoor ENP concentrations of up to 106cm-3 in a 300m3 production room after only 60s. The fast dispersal in the room was followed by an exponential decrease in number concentration after the emission event. Under conditions like those observed - rapid dispersal and good mixing - a single measurement device alone can provide valuable information for an ENP exposure assessment. A one-box model adequately reflected measured number concentrations (r2>0.99). The ENP emission rates to the workplace were estimated between 2.5·1011 and 6·1012s-1 for the three emission scenarios. The worst case emission rate at the production zone was also estimated at 2·1013s-1 with a stoichiometric calculation based on the precursor input, density and particle size. ENP intake fractions were 3.8-5.1·10-4 inhaled ENP per produced ENP in the investigated setting. These could only be substantially lowered by leaving the production room within a few minutes after the emission event. © 2012 Elsevier B.V.

Stubhan T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Li N.,Friedrich - Alexander - University, Erlangen - Nuremberg | Luechinger N.A.,Nanograde Ltd. | Halim S.C.,Nanograde Ltd. | And 3 more authors.
Advanced Energy Materials | Year: 2012

We demonstrate solution-processed tungsten trioxide (WO3) incorporated as hole extraction layer (HEL) in polymer solar cells (PSCs) with active layers comprising either poly(3-hexylthiophene) (P3HT) or poly[(4,4′-bis(2-ethylhexyl)dithieno[3,2-b:2′,3′-d]silole)-2, 6-diyl-alt-(4,7-bis(2-thienyl)-2,1,3-benzothiadiazole)-5,50-diyl] (Si-PCPDTBT) mixed with a fullerene derivative. The WO3 layers are deposited from an alcohol-based, surfactant-free nanoparticle solution. A short, low-temperature (80 °C) annealing is sufficient to result in fully functional films without the need for an oxygen-plasma treatment. This allows the application of the WO3 buffer layer in normal as well as inverted architecture solar cells. Normal architecture devices based on WO3 HELs show comparable performance to the PEDOTPSS reference devices with slightly better fill factors and open circuit voltages. Very high shunt resistances (over 1 MO cm2) and excellent diode rectification underline the charge selectivity of the solution-processed WO3 layers. © 2012 WILEY-VCH Verlag GmbH & Co. KGaA.

Li N.,Friedrich - Alexander - University, Erlangen - Nuremberg | Stubhan T.,Friedrich - Alexander - University, Erlangen - Nuremberg | Luechinger N.A.,Nanograde Ltd. | Halim S.C.,Nanograde Ltd. | And 4 more authors.
Organic Electronics: physics, materials, applications | Year: 2012

Solution processing is a convenient method and also the guarantee for low cost and large-scale organic photovoltaic (OPV) production. It was recently suggested that the absorption of OPV devices can be spectrally extended by introducing ternary semiconductor blends, where a second donor with a complementary absorption spectrum is added into the active layer. In this manuscript we demonstrate the successful replacement of poly(3,4- ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) by low temperature solution processed tungsten trioxide (WO 3) nanoparticles for inverted OPV devices based on either poly(3-hexylthiophene) (P3HT): phenyl-C61-butyric acid methyl ester (PCBM) or P3HT: poly[2,1,3-benzothiadiazole-4,7-diyl[4,4- bis(2-ethylhexyl)-4H-cyclopenta[2,1-b:3,4-b′]dithiophene-2,6-diyl]] (Si-PCPDTBT):PCBM active layers. These WO 3 nanoparticles can serve as fully functional anode buffer layers in inverted OPV devices without further treatment, while showing comparable functionality as PEDOT:PSS layers. © 2012 Elsevier B.V. All rights reserved.

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