InGaP/GaAs/Ge triple-junction solar cells with ZnO nanowires

ZnO nanowire (NW) grown on triple-junction (TJ) solar cells via the hydrothermal growth method to enhance efficiency is investigated. In this paper, experimental results indicate that TJ solar cells with ZnO NW as an antireflection (AR) coating have the lowest reflectance in the short wavelength spectrum, as compared with those of bare TJ solar cells (without AR coating) and solar cells with SiN_x and TiO₂/Al₂O ₃ AR coatings. ZnO NW has the lowest light reflection among all experimental samples, especially in the range of ultraviolet to green light (300-500 nm). It was found that ZnO NW could enhance the conversion efficiency by 6.92%, as compared with the conventional TJ solar cell. In contrast, SiN _x and TiO₂/Al₂O₃ AR coatings could only enhance the conversion efficiency by 3.72% and 6.46% increase, respectively. The encapsulated results also suggested that the cell with ZnO NW coating could provide the best solar cell performances. Furthermore, all samples are measured at tilt angles of 0°-90°and results show that the solar cells with ZnO NW have the highest efficiency at all tilt angles. Furthermore, a small NW diameter increases light absorption.