Plasmon-active silver nanoparticle layers were included in solution-processed bulk-heterojunction solar cells. Nanoparticle layers were fabricated using vapor-phase deposition on indium tin oxide electrodes. Owing to the increase in optical electrical field inside the photoactive layer, the inclusion of such particle films lead to increased optical absorption and consequently increased photoconversion at solar-conversion relevant wavelengths. The resulting solar energy conversion efficiency for a bulk heterojunction photovoltaic device of poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester was found to increase from 1.3%±0.2% to 2.2%±0.1% for devices employing thin plasmon-active layers. Based on six measurements, the improvement factor of 1.7 was demonstrated to be statistically significant.

The field of paper-based microfluidics has experienced rapid growth over the past decade. Microfluidic paper-based analytical devices (μPADs), originally developed for point-of-care medical diagnostics in resource-limited settings, are now being applied in new areas, such as environmental analyses. Low-cost paper sensors show great promise for on-site environmental analysis; the theme of ongoing research complements existing instrumental techniques by providing high spatial and temporal resolution for environmental monitoring. This review highlights recent applications of μPADs for environmental analysis along with technical advances that may enable μPADs to be more widely implemented in field testing.

Random silver nanohole films were created through colloidal lithography techniques and metal vapor deposition. The transparent electrodes were characterized by uv-visible spectroscopy and incorporated into an organic solar cell. The test cells were evaluated for solar power-conversion efficiency and incident photon-to-current conversion efficiency. The incident photon-to-current conversion efficiency spectra displayed evidence that a nanohole film with 92nm diameter holes induces surface-plasmon-enhanced photoconversion. The nanohole silver films demonstrate a promising route to removing the indium tin oxide transparent electrode that is ubiquitous in organic optoelectronics.

Solid fi lms of a water-soluble dicationic perylene diimide salt, perylene bis(2ethyltrimethylammonium hydroxide imide), Petma + OH − , are strongly doped n-type by dehydration and reversibly de-doped by hydration. The hydrated fi lms consist almost entirely of the neutral perylene diimide, PDI, while the dehydrated fi lms contain ∼ 50% PDI anions. The conductivity increases by fi ve orders of magnitude upon dehydration, probably limited by fi lm roughness, while the work function decreases by 0.74 V, consistent with an n-type doping density increase of ∼ 12 orders of magnitude. Remarkably, the PDI anions are stable in dry air up to 120 ° C. The work function of the doped fi lm, ϕ (3.96 V vs. vacuum), is unusually negative for an O 2 -stable contact. Petma + OH − is also characterized as an interfacial layer, IFL, in two different types of organic photovoltaic cells. Results are comparable to state of the art cesium carbonate IFLs, but may improve if fi lm morphology can be better controlled. The fi lms are stable and reversible over many months in air and light. The mechanism of this unusual self-doping process may involve the change in relative potentials of the ions in the fi lm caused by their deshielding and compaction as water is removed, leading to charge transfer when dry. 456 www.MaterialsViews.com www.advenergymat.de

Nanoaperture arrays in a silver film were quantitatively evaluated, for the first time, to determine the absolute Raman scattering enhancement factors as a function of aperture lattice spacing using a nonresonant analyte. The arrays, with 200 nm diameter apertures and varying spacing in a 50 nm thick silver film, resulted in an average area-corrected SERS enhancement factor of ( 6( 3) × 10 7 for 514.5 nm excitation. Comparison between theory and experiment provided critical insight into the magnitude and origin of enhancement in these nanoaperture arrays as a function of lattice spacing. The measured enhancement factor was attributed to two distinct sources: a factor of 10 5 from nm scale roughness associated with the Ag film in the absence of the nanoapertures and a factor of 6 × 10 2 associated with plasmons localized near the aperture edges.