Improving performance of crystalline silicon ultrathin solar cells using multi snowflake fractal nano-structures

Abstract In this paper, we propose a novel architecture for an ultrathin-film solar cell, integrating silicon multi-snowflake fractals into the electron-transport layer. In the proposed structure, each dielectric snowflake fractal is designed to trap sunlight within specific wavelength bands using multiple orders of Mie resonances and branch coupling, collectively covering the solar cell's operation bandwidth. This structure is numerically investigated using full-wave simulation with the FDFD method and by solving the drift and diffusion equations. The calculations demonstrate enhanced absorption across the whole wavelength range of 300 nm to 1100 nm, leading to an increased photo-generated current for both Transverse Electric (TE) and Transverse Magnetic (TM) polarizations of the incident light and at various angles of incidence. Simulation results illustrate a short-circuit current of 15.37 mA/cm² for the proposed structure, which is enhanced by a factor of 5.12 compared to a simple solar cell without fractal nanostructures inside.