Compact wideband FSS-absorber-based low-RCS reflectarray antenna

This paper presents a method to realize compact broadband low-RCS ReflectArray(RA)antenna based on a Frequency Selective Surface(FSS)absorber and a reflective metasurface.Such an FSS absorber consists of a resistance-loaded lossy layer and an FSS layer,which is utilized to reach an absorption-transmission response.The bottom reflective metasurface works as a phase array,reshaping the quasi-sphere wave from the feeding antenna into the quasi-plane wave.As a demonstration,the low-RCS RA antenna is simulated,fabricated,and measured.The simulated and measured results show that the developed low-RCS RA antenna has an aperture efficiency of 42.7%and a gain of 25.4 dBi in the X band.In the meantime,it simultaneously reaches the 10 dB RCS reduction for the orthogonal polarizations at the S and C bands,corresponding to a fractal bandwidth of 120%.Specifically,the adopted patch-feeding antenna makes the RA antenna more compact than the horn-feed conventional ones.Furthermore,the proposed RA antenna uses a few layers of substrates,making it lower in cost and easier for fabrication.The proposed design may have potential application in integrated stealth communication systems.

Perovskite Solar Cells toward Eco-Friendly Printing

Eco-friendly printing is important for mass manufacturing of thin-film photovoltaic(PV)devices to preserve human safety and the environment and to reduce energy consumption and capital expense.However,it is challenging for perovskite PVs due to the lack of eco-friendly solvents for ambient fast printing.In this study,we demonstrate for the first time an eco-friendly printing concept for high-performance perovskite solar cells.Both the perovskite and charge transport layers were fabricated from eco-friendly solvents via scalable fast blade coating under ambient conditions.The perovskite dynamic crystallization during blade coating investigated using in situ grazing incidence wide-angle X-ray scattering(GIWAXS)reveals a long sol-gel window prior to phase transformation and a strong interaction between the precursors and the eco-friendly solvents.The insights enable the achievement of high quality coatings for both the perovskite and charge transport layers by controlling film formation during scalable coating.The excellent optoelectronic properties of these coatings translate to a power conversion efficiency of 18.26%for eco-friendly printed solar cells,which is on par with the conventional devices fabricated via spin coating from toxic solvents under inert atmosphere.The eco-friendly printing paradigm presented in this work paves the way for future green and highthroughput fabrication on an industrial scale for perovskite PVs.