Copper and Transparent-Conductor Reflectarray Elements on Thin-Film Solar Cell Panels

TL;DR

This paper demonstrates the feasibility of integrating reflectarray antennas on thin-film solar panels by balancing optical transparency and microwave conductivity, achieving high efficiency and transparency with both copper and transparent conductors.

Contribution

It introduces a design approach for reflectarray unit cells on solar panels that maintains high optical transparency and low microwave loss, enabling efficient integration.

Findings

Unit cells with over 270° phase range achieved.

Average microwave loss of -2.45dB with copper, -0.25dB with transparent conductors.

Optical transparency of 85-90% maintained in the visible spectrum.

Abstract

This work addresses the integration of reflectarray antennas (RA) on thin film Solar Cell (SC) panels, as a mean to save real estate, weight, or cost in platforms such as satellites or transportable autonomous antenna systems. Our goal is to design a good RA unit cell in terms of phase response and bandwidth, while simultaneously achieving high optical transparency and low microwave loss, to preserve good SC and RA energy efficiencies, respectively. Since there is a trade-off between the optical transparency and microwave surface conductivity of a conductor, here both standard copper and transparent conductors are considered. The results obtained at the unit cell level demonstrates the feasibility of integrating RA on a thin-film SC, preserving for the first time good performance in terms of both SC and RA efficiency. For instance, measurement at X-band demonstrate families of cells providing a phase range larger than 270{\deg} with average microwave loss of -2.45dB (resp. -0.25dB) and average optical transparency in the visible spectrum of 90% (resp. 85%) using transparent conductive multilayer (resp. a copper layer).