Absorption enhancement of thin film solar cells using back binary metallic grating

We reported in this work that light absorption can be significantly enhanced in an a-Si thin film solar cell with a nano binary metallic grating patterned on the bottom side. The enhancement is mainly due to combination of several kinds of optical modes. Cavity mode, at the transverse and longitudinal cavities and surface plasmon mode, propagating along the interface of silicon and silver are the main modes contributing to the enhancement. Some key parameters including grating period, width, height and active layer thickness are optimized. The integrated absorption rate of the optimized system reaches 76.55 % for the wavelength range from 300 to 950 nm under AM1.5G spectrum.