A practical wave-optical hemispheroidal nanostructure strategy for photonic-enhanced thin film solar cells

The interaction between light and wavelength-sized photonic nanostructure is highly promising for light management applied to thin-film photovoltaics (PVs). In this work, we put forward a practical wave-optical dielectric hemispheroidal nanostructure strategy under cost-effective anodic oxidation approach and substrate transfer method. By adjusting the oxidation voltage, periodic hemispheroidal nanostructure with diametral scale over 650 nm was obtained. Due to their wavelength-scale dimension, enhanced diffraction behavior and guided resonance were identified through finite-difference-time-domain (FDTD) simulation resulting in significant forward-scattering capabilities. The coherent optical performance was investigated experimentally and theoretically. To leverage the benefits of hemispheroidal nanostructure, amorphous silicon absorb layer and solar cell were fabricated. Compared with the planer structure, the developed hemispheroidal nanostructure could significantly improve the absorption of a-Si:H layer via light management with a 10.97% enhancement in the overall external quantum efficiency. Effective improvements in Voc and FF performances were also obtained in comparison to an etched AZO structure with high surface roughness. As the first demonstration, it was found that the hemispheroidal nanostructure by coating on the surface of a-Si:H thin film solar cells led to 7.79% and 7.38% enhancements respectively in overall energy conversion efficiency in comparison to the planar and the etched AZO structure.