Large Absorption Enhancement in Ultrathin Solar Cells Patterned by Metallic Nanocavity Arrays

A new type of light trapping structure utilizing ring-shaped metallic nanocavity arrays is proposed for the absorption enhancement in ultrathin solar cells with few photonic waveguide modes. Dozens of times of broadband absorption enhancement in the spectral range of 700 to 1100 nm is demonstrated in an ultrathin Si₃N₄/c-Si/Ag prototype solar cell by means of finite-difference time-domain (FDTD) simulation, and this dramatic absorption enhancement can be attributed to the excitation of plasmonic cavity modes in these nanocavity arrays. The cavity modes optimally compensate for the lack of resonances in the longer wavelength range for ultrathin solar cells, and eventually a maximum J_sc enhancement factor of 2.15 is achieved under AM 1.5G solar illumination. This study opens a new perspective for light management in thin film solar cells and other optoelectronic devices.