At present, the light conversion efficiencies achievable with organic photovoltaic (OPV) technology are significantly
below those seen in inorganic materials. The efficiency of OPV devices is limited by material properties; the high energy
and narrow-band absorption of organic semiconductors results in inefficient harvesting of solar radiation, while the low
charge carrier mobility in organic semiconductors limits the possible active layer thickness. Utilization of plasmonic
structures in or around the OPV active layer has been suggested as a way to achieve a higher conversion efficiency in
thin film photovoltaic devices. Our theoretical and experimental results indicate that aluminum-based plasmonic
nanostructures hold significant promise for conversion efficiency enhancement in OPV devices. The high plasma
frequency of aluminum permits a nanoparticle concentration close to the percolation threshold, which results in a
broader band of plasmonically enhanced absorbance in OPV material and better overlap between the natural absorption
bands of OPV materials and the plasmonic band of the metal nanostructure than what is achievable with gold or silver
plasmonic structures. This is demonstrated experimentally by embedding aluminum nanoparticles in P3HT:PCBM
layers, which leads to a significantly enhanced absorption over a broad range of wavelengths. While aluminum
nanoparticles are prone to oxidation, our results also indicate the path to stabilization of these particles via proper surface
functionalization.
Ultrafast all optical magnetization switching in GdFeCo layers on the basis of Inverse Faraday Effect (IFE) was
demonstrated recently and suggested as a possible path toward next generation magnetic data storage medium with much
faster writing time. However, to date, the demonstrations of ultrafast all-optical magnetization switching were performed
with powerful femtosecond lasers, hardly useful for practical applications in data storage and data processing. Here we
show that utilization of IFE enhancement in plasmonic nanostructures enables fast all-optical magnetization switching
with smaller/cheaper laser sources with longer pulse durations. Our modeling results predict significant enhancement of
IFE around all major types of plasmonic nanostructures for a circularly polarized incident light. Unlike the IFE in
uniform bulk materials, nonzero value of IFE is predicted in plasmonic nanostructures even with a linearly polarized
excitation. Experimentally, all-optical magnetization switching at 20 times lower laser fluence and roughly 100 times
lower value of laser fluence/pulse duration ratio is demonstrated in plasmonic samples to verify the model predictions.
The path to achieve higher levels of enhancement experimentally is discussed.
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