Design and demonstration of light trapping for Ge:Si solar cell below Si solar cell in a multi-junction solar cell system

A light trapping design which increases the effective optical path length by a factor of 21 is designed for Ge:Si solar cell. Experimental results achieved an increase in effective optical path length of 17X which led to a Jsc of 7.91mA/cm² for 88%Ge content Ge:Si solar cell below Si at one sun. Jsc is 120% higher than that of solar cells without light trapping. Below Si at 30 suns, the efficiency of 88%Ge content Ge:Si solar cell with light trapping reached 1.37% which is 60% of the theoretical efficiency maximum.