Optical absorption enhancement in a hybrid system photonic crystal - Thin film for photovoltaic applications

A hybrid approach for light trapping using photonic crystal (PC) nanostructures (nanorods, nanopillars or nanoholes) on top of an ultra-thin film is presented. The combination of a nanopatterned layer with a thin substrate shows an enhanced optical absorption than equivalent films without patterning and can compete in performance with nanostructured systems without a substrate. The designs are tested in four relevant materials: amorphous silicon (a-Si), crystalline silicon (Si), gallium arsenide (GaAs) and indium phosphide (InP). A consistent enhancement is observed for all of the materials when using a thin hybrid system (300 nm) even compared to the non-patterned thin film with an anti-reflective coating (ARC). A realistic solar cell structure composed of a hybrid system with a layer of indium tin oxide (ITO) an ARC and a back metal layer is simulated, showing an 13% of improvement for the nanostructured device.