Effect on the opto-electronic performance of thin- film solar cells due to structural defects in periodic arrays of plasmonic metal nanoparticles deposited on the solar cells

This computational study models some of the possible structural defects that may occur when fabricating homogenous metal nanoparticle arrays on top of a silicon based thin-film solar cell (TFSC) and investigates their effect on the opto-electronic performance of the cell when compared to a "perfect" array (i.e., with no structural defects). To conduct this study, an array consisting of five homogenous spherical silver nano-particles having diameter of 50nm was designed as the repeating unit in a two-dimensional homogenous nanoparticle array. Finite Difference Time Domain (FDTD) simulations were first carried out to determine the optimal pitch size (inter- particle distance) for the "perfect" array based on the highest short circuit current density generated. Subsequently, three different types of defects in the repeating unit were investigated: (i) the effect of missing particles; (ii) the effect of having different particle sizes, and (iii) the effect of addition of impurities. The results obtained showed a decrease in the performance of the solar cell with the creation of most of such defects with a few notable exceptions. The results highlight the importance of considering structural defects in arrays of plasmonic nanoparticles as an important design parameter when designing such "plasmonic" thin-film solar cells.