Broadband antireflective coatings for high efficiency InGaP/GaAs/InGaAsP/InGaAs multi junction solar cells

Abstract

Design and fabrication of antireflection coatings (ARCs) was performed to maximize the photocurrent of III-V solar cells based on InGaP, GaAs, InGaAsP, and InGaAs. The current-limiting behavior of multi-junction solar cells allowed only the specific design of ARCs to improve the total current density of multi junction solar cells, which enabled thin and efficient antireflection layers to achieve their full potential. ARCs were designed for InGaP/GaAs and InGaAsP/InGaAs double junction solar cells and InGaP/GaAs/InGaAsP/InGaAs quadruple junction solar cells. From the ARC design results, the best solar cell reflectance at the region of interest appeared to be 1.44% for InGaP/GaAs solar cells, 2.17% for InGaAsP/InGaAs, and 0.48% for the quadruple junction solar cells. To achieve the preferred refractive index for the ARC structures, nanostructures fabricated via glancing angle deposition were utilized. With ARC fabricated structures, InGaP/GaAs double junction solar cells yielded a power conversion efficiency of 13.3%, which was 1.34 times higher than that of cells without ARC (9.91%). Additionally, calculation results for the various ARC designs using dual and triple material systems were provided to increase their applicability.