Enhanced omnidirectional photovoltaic performance of solar cells using multiple-discrete-layer tailored- and low-refractive index anti-reflection coatings

An optimized four-layer tailored- and low-refractive index anti-reflection (AR) coating on an inverted metamorphic (IMM) triple-junction solar cell device is demonstrated. Due to an excellent refractive index matching with the ambient air by using tailored- and low-refractive index nanoporous SiO₂ layers and owing to a multiple-discrete-layer design of the AR coating optimized by a genetic algorithm, such a four-layer AR coating shows excellent broadband and omnidirectional AR characteristics and significantly enhances the omnidirectional photovoltaic performance of IMM solar cell devices. Comparing the photovoltaic performance of an IMM solar cell device with the four-layer AR coating and an IMM solar cell with the conventional SiO₂/TiO ₂ double layer AR coating, the four-layer AR coating achieves an angle-of-incidence (AOI) averaged short-circuit current density, J_SC, enhancement of 34.4%, whereas the conventional double layer AR coating only achieves an AOI-averaged J_SC enhancement of 25.3%. The measured reflectance reduction and omnidirectional photovoltaic performance enhancement of the four-layer AR coating are to our knowledge, the largest ever reported in the literature of solar cell devices. A multiple-discrete-layer omnidirectional and broadband anti-reflection (AR) coating is demonstrated on an inverted metamorphic (IMM) triple-junction solar cell device. Due to an excellent refractive index matching with the ambient air and a genetic algorithm optimization of the discrete refractive index profile, the IMM device employing a four-layer AR coating shows better photovoltaic performance at all incident angles (0°-80°) than an IMM device employing a traditional double layer AR coating.