In this paper, we demonstrate high-density nanolithography by utilizing surface plasmons (SPs). SPs are excited on an aluminum substrate perforated with 2-D hole arrays using a near UV light source in order to resolve sub-wavelength features with high transmission. Our lithography experiments using a 365 nm wavelength light source demonstrate 90 nm dot array patterns on a 170 nm period, well beyond the diffraction limit of far-field optical lithography. In far-field transmission measurements, strong UV light transmission and the wavelength-dependent transmission are observed, which confirms the contribution of SPs. Furthermore, an exposure with larger spacing between the mask and photoresist has been explored for potential noncontact lithography.

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We report systematic design and formation of plasmonic perovskite solar cells (PSCs) by integrating Au@TiO core-shell nanoparticles (NPs) into porous TiO and/or perovskite semiconductor capping layers. The plasmonic effects in the formed PSCs are examined. The most efficient configuration is obtained by incorporating Au@TiO NPs into both the porous TiO and the perovskite capping layers, which increases the power conversion efficiency (PCE) from 12.59% to 18.24%, demonstrating over 44% enhancement, compared with the reference device without the metal NPs. The PCE enhancement is mainly attributed to short-circuit current improvement. The plasmonic enhancement effects of Au@TiO core-shell nanosphere photovoltaic composites are explored based on the combination of UV-vis absorption spectroscopy, external quantum efficiency (EQE), photocurrent properties, and photoluminescence (PL). The addition of Au@TiO nanospheres increased the rate of exciton generation and the probability of exciton dissociation, enhancing charge separation/transfer, reducing the recombination rate, and facilitating carrier transport in the device. This study contributes to understanding of plasmonic effects in perovskite solar cells and also provides a promising approach for simultaneous photon energy and electron management.

A new type of molecular fragmentation induced by femtosecond intense laser at the intensity of 2 x 10(14) W/cm2 is reported. For the parent molecule of methane, ethylene, n-butane, and 1-butene, fluorescence from H (n = 3-->2), CH (A 2Delta, B 2Sigma-, and C 2Sigma+-->X 2Pi), or C2 (d 3Pi g-->a 3Pi u) is observed in the spectrum. It shows that the fragmentation is a universal property of neutral molecule in the intense laser field. Unlike breaking only one or two chemical bonds in conventional UV photodissociation, the fragmentation caused by the intense laser undergoes vigorous changes, breaking most of the bonds in the molecule, like an explosion. The fragments are neutral species and cannot be produced through Coulomb explosion of multiply charged ion. The laser power dependence of CH (A-->X) emission of methane on a log-log scale has a slope of 10 +/- 1. The fragmentation is thus explained as multiple channel dissociation of the superexcited state of parent molecule, which is created by multiphoton excitation.

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Achieving high open-circuit voltage and high short-circuit current density simultaneously is a big challenge in the development of highly efficient perovskite solar cells, due to the complex excitonic nature of hybrid organic-inorganic semiconductors. Herein, we developed a facile and effective method to fabricate efficient plasmonic PSC devices. The solar cells were prepared by incorporating Au nanoparticles (NPs) into mesoporous TiO films and depositing a MgO passivation film on the Au NP-modified mesoporous titania via wet spinning and pyrolysis of magnesium salt. The PSCs obtained by combining Au NPs and MgO demonstrated a high power conversion efficiency of 16.1%, with both a high open-circuit voltage of 1.09 V and a high short-circuit current density of 21.76 mA cm. The device achieved a 34.2% improvement in the power conversion efficiency compared with a device based on pure TiO. Moreover, a significant improvement of the UV stability in the perovskite solar cell was achieved due to the combined use of Au NPs and insulating MgO. The fundamental optics and physics behind the regulation of energy flow in the perovskite solar cell and the concept of using Au NPs and MgO to improve the device performance were explored. The results indicate that the combined use of Au NPs and a MgO passivation film is an effective way to design high performance and high stability organic-inorganic perovskite photovoltaic materials.

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