Modelling the temperature induced degradation kinetics of the short circuit current in organic bulk heterojunction solar cells

In organic bulk heterojunction solar cells, the nanoscale morphology of interpenetrating donor-acceptor materials and the resulting photovoltaic parameters alter as a consequence of prolonged operation at temperatures above the glass transition temperature. Thermal annealing induces clustering of the acceptor material and a corresponding decrease in the short circuit current. A model based on the kinetics of Ostwald ripening is proposed to describe the thermally accelerated degradation of the short circuit current of solar cells with poly(2-methoxy-5-(3,7-dimethyloctyloxy)-1,4-phenylenevinylene) (MDMO-PPV) as donor and (6,6)-phenyl C61-butyric acid methyl ester (PCBM) as acceptor. The activation energy for the degradation is determined by an Arrhenius model, allowing to perform shelf life prediction. ©2010 American Institute of Physic

Large-grained poly-Si films on ZnO:Al coated glass substrates

Thin film polycrystalline silicon (poly-Si) films have been fabricated by the aluminium-induced layer exchange (ALILE) process on ZnO:Al coated glass. The formation of the poly-Si films was observed during the annealing process using an optical microscope. Poly-Si films formed on ZnO:l coated glass consist of high-quality poly-Si material, as evidenced by Raman measurement. The average grain size of the poly-Si films slightly increases with decreasing annealing temperature. The formation of poly-Si films on ZnO:Al coated glass led to a preferential (001) orientation at all annealing temperatures (425 degrees C similar to 525 degrees C). (C) 2007 Elsevier B.V. All rights reserved

Silica filled poly(1-trimethylsilyl-1-propyne) nanocomposite membranes: Relation between the transport of gases and structural characteristics

The performance of poly(1-trimethylsilyl-1-propyne) (PTMSP)/silica nanocomposites was studied for membranes with a filler content between 0 and 50 wt%. An increase in permeability and a decrease in vapor selectivity was measured with increasing filler content. The free volume sizes and interstitial mesopore sizes of the composites were determined by use of positron annihilation lifetime spectroscopy (PALS). In addition to an increase in large free volume size with increasing filler content, interstitial mesopores were observed in all PTMSP/silica nanocomposites. The size of these interstitial cavities, located between the particles of a silica agglomerate, was increasing with increasing filler concentration. The presence of these agglomerates was visualized by TEM. The existence of the cavities was confirmed by nitrogen adsorption measurements. The hydrogen, nitrogen and propane permeability was clearly correlated with the size of the interstitial mesopores. (c) 2005 Elsevier B.V. All rights reserved