No abstract

Wavelength-structured transparent conductive oxide (TCO) electrodes are highly promising to improve both the optical and electrical performance of photovoltaic (PV) devices, due to wave-optical light-trapping (LT) effects and higher TCO volume without increasing optical losses.Herein we present a complete study of the benefits of microstructured IZO contacts applied on amorphous-silicon (a-Si) thin film solar cells. The IZO LT structures were integrated by an innovative colloidal lithography process on the front contact of the cells, resulting in enhancements of 26.7% in photocurrent, with respect to planar reference cells, when using an ultra-thin (30 nm) flat IZO layer between the LT structures and the a-Si absorber. However, the best efficiency enhancement (23.1%) was attained with an optimized thickness of 190 nm for this layer, due to a more favorable combination of optical and electrical gains.In view of the application of this LT strategy in flexible PV devices operating under bending, the angular response of the cells was studied for 0-90º incidence angles. This showed that the LT enhancements are generally higher at oblique incidence, reaching 53.2% and 52%, respectively in photocurrent and efficiency, at ±70º angles with the optimized flat IZO thickness of 190 nm; and 52.2% in efficiency at ±40º with the ultra-thin thickness of 30 nm. These results are among the highest gains reported thus far for LTenhanced thin film solar cells.

No abstract

Abstract-Optical cloud networks allow for the integrated management of both optical and IT resources. In this paradigm, cloud services can be provisioned in an anycast fashion, i.e., only the source node asking for a service is specified, while it is up to the cloud control/management system to select the most suitable destination data center (DC) node. During the cloud service provisioning process resiliency is crucial in order to guarantee continuous network operations also in the presence of failures. On the one hand, a survivability strategy needs to be able to meet the availability requirements of each specific cloud service, while on the other hand it must be efficient in using backup resources. This paper proposes a restoration-based survivability strategy, which combines the benefits of both cloud service relocation and service differentiation concepts. The former is used to enhance the restorability performance (i.e., the percentage of successfully restored cloud services) offered by restoration, while the latter ensures that critical services are given the proper consideration while backup resources are assigned. The paper proposes both an ILP formulation which guarantees optimal results and a heuristic, which trades the optimality of the solution achieved by the ILP for faster processing times. Simulation results show that the average service availability and restorability performance obtained by both the ILP and the heuristic are very close to the one achievable using a protection-based strategy, but with the inherent benefit, in terms of efficient use of resources, offered by a restoration-based approach.

Core diameter mismatch structures are proposed and experimentally investigated for curvature and vibration sensing. Two configurations are suggested, one approach uses a structure formed by splicing an uncoated short section of multimode fiber between two standard single-mode fibers (SMFs) single-mode-multimode-single-mode (SMS), combined to a fiber optical mirror at its end, and the other approach uses a structure made by splicing a section of SMF between two multimode fibers (SMSMS). In the curvature analysis, the proposed SMS sensor generates the destructive interference patterns when it is bent, varying only the attenuation of the optical signal without wavelength shifts. The SMSMS vibration sensor proved to be suitable to monitor very low frequencies such as 0.1 Hz. The configuration of the proposed sensors presents several interesting features, such as easy fabrication, low cost, high efficiency, and high sensitivity. These advantages make such sensors very useful in a wide range of applications, for instance, structural health monitoring.