Efficiency improvement of flexible Cu(In,Ga)Se2 solar cells by integrating a micro-prism array transferred to soft-polydimethylsiloxane

A micro-prism array (MPA) realized on a flexible polymer substrate was integrated on the top of flexible Cu(In,Ga)Se 2 (CIGS) solar cells to overcome the optical reflection loss caused by the metal grids used with these cells. The integrated MPA refracts light normally incident to the metal grids into an active area not covered by the metal grid. This reduces the optical reflection loss, which increases the photocurrent. The original MPA structure was fabricated on a Si substrate by a combined process of dry and wet etching. The MPA structure on the Si template was transferred to soft-polydimethylsiloxane (S-PDMS) by using a stamping method. The short-current density and the power conversion efficiency of the flexible CIGS solar cell integrated with the MPA based on S-PDMS were improved by 4.9 and 5.2%, respectively, when compared with those of conventional flexible CIGS solar cell without MPA.