Effect of nanopits size and spacing on the light absorption in silicon thin film solar cells

Periodic nanopits texture has been shown to demonstrate light trapping properties and promising potential for Si thin film solar cell. In this work, the effect of size and spacing of periodic nanopits texture on the light absorption in amorphous silicon (a-Si) thin film solar cells was studied using finite difference time domain (FDTD) method. The results show that, in most cases, there is a bigger light absorption in a-Si thin film cells for larger nanopits size (≥200 nm), and the light absorption decreases with increasing nanopits spacing. A total absorptivity maximum of 70.7%, 70.8%, and 69.0% of a-Si thin film solar cell with a 300 nm thick a-Si active layer are achieved for nanopits size/spacing ratio of 400 nm/0.4, 500 nm/0, and 600 nm/0.2, respectively. The electric field intensity distribution of the a-Si thin film solar cell with periodic nanopits texture was also evaluated to offer further physical insight into their light trapping properties.