Enhanced crystallinity and film retention of P3HT thin-films for efficient organic solar cells by use of preformed nanofibers in solution

We report the preparation of films of poly(3-hexylthiophene) nanofibers suitable for fabrication of efficient multilayer solar cells by successive deposition of donor and acceptor layers from the same solvent. The nanofibers are obtained by addition of di-tert-butyl peroxide (DTBP) to a solution of P3HT in chlorobenzene. Interestingly, by varying the concentration of DTBP we are able to control both crystallinity and film retention of the spin-cast films. We also investigate the influence of the DTBP-induced crystallization on charge transport by thin-film transistor measurements, and find a more than five-fold increase in the hole mobility of nanofiber films compared to pure P3HT. We attribute this effect to the synergistic effects of increased crystallinity of the fibers and the formation of micrometer-sized fiber networks. We further demonstrate how it is possible to make use of the high film retention to fabricate photovoltaic devices by subsequent deposition of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) from a chlorobenzene solution on top of the nanofiber film. The presence of a relatively large crystalline phase strongly affects the diffusion behavior of PCBM into the P3HT film, resulting in a morphology which is different from that of common bulk heterojunction solar cells and resembles a bilayer structure, as can be inferred from comparison of the external quantum efficiency spectra. However, a high power conversion efficiency of 2.3% suggests that there is still a significant intermixing of the two materials taking place

Part I: A comparative study of bismuth-modified screen-printed electrodes for lead detection

Lead determination was carried out in the frame of the European Union project Biocop (www.biocop.org) using a bismuth-modified screen-printed electrode (Bi-SPE) and the stripping analysis technique. In order to choose a sensitive Bi-SPE for lead detection, an analytical comparative study of electrodes modified by Bi using " in situ" , " ex situ" and " bulk" procedures was carried out. On the basis of the results obtained, we confirmed that the " in situ" procedure resulted in better analytical performances with respect to not only " ex situ" but also to " Bi2O3 bulk" modified electrodes, allowing for a linear range of lead ion concentration from 0.5 to 100μgL-1 and a detection limit of 0.15μgL-1. We demonstrated that, before the Bi film deposition, an oxidative electrochemical pre-treatment of the working electrode could be useful because it eliminates traces of lead in the graphite-ink, as shown with stripping measurements. It also improves the electrochemical performance of the electrodes as demonstrated with Electrochemical Impedance Spectroscopy (EIS) measurements. The influence of different analytical parameters, such as the electrolyte solution composition (acetate buffer, chloridric acid, nitric acid, perchloric acid) and the ionic strength was investigated in order to evaluate how to treat the sample before the analysis. The morphology of prepared " in situ" Bi-SPEs was also characterized by Atomic Force Microscopy (AFM). Finally, the Bi-SPEs were used to determine the concentration of lead ions in tap and commercial water samples obtaining satisfactory values of the recovery percentage (81% and 98%)

Risultati nazionali delle varietà da malto

I risultati delle prove 2005-2006 nelle 10 località del Centro-sud e Isole hanno evidenziato buone medie produttive con la conferma a leader della varietà Prosa. I buoni risultati in generale evidenziano ulteriormente l’adattabilità di questa specie alle condizioni mediterranee

Le varietà di orzo da malto.

Nove le varietà in prova in 11 ambienti del Centro-sud e delle Isole. Buona la media produttiva (5,1 t/ha), superiore di ben 1 t/ha rispetto a quella della precedente annata. Le caratteristiche produttive e qualitative delle varietà da malto attualmente disponibili rendono l'orzo da birra una produzione interessante, anche in ragione del sostanziale deficit produttivo di orzo da birra italiano