Advanced concepts of the improved light management for solar cells and modules

Abstract

An enhanced performance of Photovoltaic Modules can be achieved by increasing the cell efficiency or by lowering the losses on module level. Basically, output power is lost when part of the incident light does not reach the solar cell. Optical elements inside the module shall redirect that light which otherwise would fall on the gap areas between cells or onto the metallization grid, respectively. To reduce these losses to a minimum, different designs of optical elements preferentially realized with hot embossing technique are investigated systematically by means of simulations. Furthermore, typically solar modules do not trace the sun movement. As the performance of optical elements is strongly related to the angle under which light incidents on the surface, the simulation model comprises several light sources, mimicking the daily movement of the sun. Under these conditions two micromachined, optical structures are evaluated with respect to fabrication tolerances occurring during hot embossing, such as lateral misalignment, tilting, shrinkage and edge rounding. Finally, a new concept to realize an advanced optics featuring a gradient in refractive index in the packaging material is presented.