All-Angle Invisibility Cloaking of Contact Fingers on Solar Cells by Refractive Free-Form Surfaces

This work demonstrates a performance improvement of state-of-the-art silicon solar cells by cloaking their metal contact fingers. The cloaking free-form surfaces are fabricated on silicon heterojunction solar cells using direct laser writing of polymers and subsequent soft imprinting. Cloaking performance is determined experimentally by measuring spatially resolved and angle-resolved current generation and the spectral response of the cell. The short-circuit current density of the cell increases by 7.3%; its power-conversion efficiency is enhanced by 9.3%. Overcompensation of the shadowing loss is found to be caused by improved light-gathering and light-trapping in the polymer layer. The experimental findings are in good agreement to ray-tracing simulations.