We demonstrate novel plasmonic organic solar cells (OSCs) by embedding an easy processible nanobump assembly (NBA) for harnessing more light. The NBA is consisted of precisely size-controlled Ag nanoparticles (NPs) generated by an aerosol process at atmospheric pressure and thermally deposited molybdenum oxide (MoO3) layer which follows the underlying nano structure of NPs. The active layer, spin-casted polymer blend solution, has an undulated structure conformably covering the NBA structure. To find the optimal condition of the NBA structure for enhancing light harvest as well as carrier transfer, we systematically investigate the effect of the size of Ag NPs and the MoO3 coverage on the device performance. It is observed that the photocurrent of device increases as the size of Ag NP increases owing to enhanced plasmonic and scattering effect. In addition, the increased light absorption is effectively transferred to the photocurrent with small carrier losses, when the Ag NPs are fully covered by the MoO3 layer. As a result, the NBA structure consisted of 40 nm Ag NPs enclosed by 20 nm MoO3 layer leads to 18% improvement in the power conversion efficiency compared to the device without the NBA structure. Therefore, the NBA plasmonic structure provides a reliable and efficient light harvesting in a broad range of wavelength, which consequently enhances the performance of organic solar cells.
In this presentation, it will be shown that the plasmonic absorption of a graphene sheet can be enhanced and perturbed in controllable ways by controlling the thickness and permittivity of the supporting substrate. We will show the results of recent experiments where 25% absorption is achieved in the plasmonic modes of a graphene sheet by carefully selecting the properties of an underlying silicon nitride substrate. We also demonstrate how additional absorption pathways can be created by modifying the surrounding dielectric environment to have optical resonances that can couple to the graphene plasmons.
We present a simple method to generate nanostructures without residual layer using detachment-based nanolithography. Spin coated organic thin film and patterned stamp such as ultraviolet (UV) curable mold were prepared. The mold and organic thin film were contacted by slight pressure (1~2 bar). While conformal contact between mold and organic thin film, the sample was heated under the glass transient temperature. After cooling to room temperature, the mold was removed from substrate, rendering a pattern organic layer without residual layer. This method can form as small as 70 nm lines.
Small particles are one of the biggest sources that cause loss in semiconductor and flat panel display industry. Therefore, it is important to control them during their manufacturing process. To achieve this goal, exact measurement of particles is first required. Laser light scattering is the most widely used technique for diagnosis of particles because it does not disturb flow field and enables real time and spatially resolved analysis. Measurement of nonspherical aggregates comprised of small primary particles is difficult compared with spherical particles because they have very complex morphology. In addition, most researches on aggregates using light scattering are limited to point measurement, which requires much time to inspect large area and is difficult to observe unsteady phenomenon. Motivated by this, we have developed a laser light scattering method for simultaneous measurement of spatial distributions of aggregate size and morphology.
Silica aggregates that were generated in Methane/air premixed flame were used as test particles. Multiangular planar light scattering measurement was carried out using a sheet beam of Ar ion laser and an intensified charge coupled device (ICCD) camera as a light source and a detector, respectively. The result was interpreted based on the Rayleigh-Debye-Gans scattering theory for fractal aggregates to obtain the mean radius of gyration and fractal dimension that are the parameters characterizing aggregate size and morphology. The suitability of our new technique was confirmed by experiment using conventional light scattering.
KEYWORDS: Particles, Solids, Heat flux, Chemical reactions, Deposition processes, Data modeling, Optoelectronic devices, Chemical vapor deposition, Chemical analysis, Silica
A study has been carried out for the particle deposition during the Modified Chemical Vapor Deposition (MCVD) process. The analysis includes thermophoretic particle transport in the gas flow inside the tube and heat transfer through the solid layer with considering variable properties for both gas and solid regions. A notable feature of the study is to consider the effects of the periodic heating due to repeatedly traversing of the torch including the effects of the increasing solid layer thickness as the particles deposit. The localized heating of the moving torch is modelled as a gaussian heat flux boundary condition on the tube wall and the surface temperature distribution and the deposition efficiency results in good agreement with the existing experimental data. Of particular interest are the effects of torch speeds and solid layer thicknesses on the efficiency and the rate of deposition of particles, and the tapered length.
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