Determining the internal quantum efficiency of highly efficient polymer solar cells through optical modeling

A power conversion efficiency of 4.2% (AM1.5, 1000 W/m(2)) is measured for an organic solar cell based on an active layer of an alternating copolymer, containing a fluorene and a benzothiadiazole unit with two neighboring thiophene rings, and a fullerene derivative. Using optical modeling, the absorption profile in the active layer of the solar cell is calculated and used to calculate the maximum short circuit current. The calculated currents are compared with measured currents from current-voltage measurements for various film thicknesses. From this the internal quantum efficiency is estimated to be 75% at the maximum for the best device. (c) 2007 American Institute of Physics

Flood Impacts on Road Transportation Using Microscopic Traffic Modelling Techniques

This is the author accepted manuscript. The final version is available from Springer via the DOI in this recordThis paper proposes a novel methodology for modelling the impacts of floods on traffic. Often, flooding is a complex combination of various causes (coastal, fluvial and pluvial). Further, transportation systems are very sensitive to external disturbances. The interactions between these two complex and dynamic systems have not been studied in detail so far. To address this issue, this paper proposes a methodology for a dynamic integration of a flood model (MIKE FLOOD) and a microscopic traffic simulation model (SUMO). The flood modelling results indicate which roads are inundated for a period of time. The traffic on these links will be halted or delayed according to the flood characteristics—extent, propagation and depth. As a consequence, some of the trips need to be cancelled; some need to be rerouted to unfavourable routes; and some are indirectly affected. A comparison between the baseline and a flood scenario yields the impacts of that flood on traffic, estimated in terms of lost business hours, additional fuel consumption and additional CO2 emissions. The proposed methodology will be further developed as a workable tool to evaluate the flooding impact on transportation network at city scale automatically.Research on the PEARL (Preparing for Extreme And Rare events in coastaL regions) project is funded by the European Commission through Framework Programme 7, Grant Number 603663

Fossil fuel prices and the economic and budgetary challenges of a small energy-importing economy : the case of Portugal

This paper examines the economic and budgetary impacts of fuel prices using a dynamic general equilibrium model of the Portuguese economy which high- lights the mechanisms of endogenous growth and includes a detailed modeling of the public sector. The fuel price scenarios are based on forecasts by the US Department of Energy (DOE-US) and the International Energy Agency (IEA-OECD) and represent a wide range of projections for absolute and relative fossil fuel prices. In terms of the long term economic impact, our results suggest a 1.9 % drop in GDP in the DOE-US scenario and 1.6 % in the IEA-OECD scenario. As to the budgetary impact, higher fuel prices lead to lower tax revenues, which, coupled with a reduction in public spending, translate into lower public deficits. Accordingly, increasing fuel prices create an important policy trade off in that they can contribute to reducing the public deficit while hindering economic growth. We find that fairly strong incentives for wind energy can reduce the economic impact of fuel prices by 14.2 % in the DOE-US price scenario and 18.5 % reduction in the IEA-OECD price scenario. Finally, our results highlight the importance of public sector spending decisions and the mechanisms of endogenous growth in understanding the impact of fossil fuel prices. Indeed, a scenario of higher fuel prices would, with exogenous public decisions and exogenous economic growth assumptions, result in substantially smaller economic effects and yield adverse budgetary effects.info:eu-repo/semantics/publishedVersio

Photoemission Spectroscopy and Atomic Force Microscopy Investigation of Vapor Phase Co-Deposited Silver/Poly(3-hexylthiophene) Composites

Nanocomposite matrices of silver/poly(3-hexylthiophene) (P3HT) were prepared in ultrahigh vacuum through vapor-phase co-deposition. Change in microstructure, chemical nature and electronic properties with increasing filler (Ag) content were investigated using in-situ XPS and UPS, and ambient AFM. At least two chemical binding states occur between Ag nanoparticles and sulfur in P3HT at the immediate contact layer but no evidence of interaction between Ag and carbon (in P3HT) was found. AFM images reveal a change in Ag nanoparticles size with concentration which modifies the microstructure and the average roughness of the surface. Under co-deposition, P3HT largely retains its conjugated structures, which is evidenced by the similar XPS and UPS spectra to those of P3HT films deposited on other substrates. We demonstrate here that the magnitude of the barrier height for hole injection and the position of the highest occupied band edge (HOB) with respect to the Fermi level of Ag can be controlled and changed by adjusting the metal (Ag) content in the composite. Furthermore, UPS reveals distinct features related to the C 2p (Sigma states) in the 5-12 eV regions, indicating the presence of ordered P3HT which is different from solution processed films.Comment: Scudier and Wei provided equal contributio

The Impact of Perceived Expectations and Uncertainty on Firm Investment

This paper analyses the (differential) impact of perceived expectations and uncertainty on investment spending in small and large firms. We analyse two types of investment, viz. aggregate investment and investment in energy-saving technologies, using Dutch firm level data. The results show that expectations and uncertainty about input- and output prices and domestic demand have substantial but different effects on investment spending in firms of different sizes. Furthermore, we find evidence, at least for small firms, that there are important differences between the effects of uncertainty about input and output variable