Design of ultra-broadband antireflection coatings utilizing integrated moth-eye structures for multi-junction device applications

Ultra-broadband Antireflection Coatings (ARCs) are essential to realizing the potential efficiency gains of four-junction photovoltaic devices that absorb to longer wavelengths than state-of-the-art three-junction cells. In this work, we examine a novel design that integrates a nanostructured antireflection layer with a multilayer ARC. Using optical models, we find that this hybrid approach can reduce the reflected AM1.5D power by 10-45 W/m² compared to conventional thin-film ARCs. A hybrid ARC is designed and fabricated on a sample consisting of approximately 1μm of indium gallium phosphide (InGaP) on gallium arsenide (GaAs). For the hybrid coating, we measure a reflection loss of just 23.9 W/m² corresponding to less than a 3% power reflection.