Double sided minority carrier collection in silicon solar cells

Several new cell structures are under development in order to lower the module fabrication cost by designing cells for easier encapsulation. Most of these structures have a carrier collecting emitter adjacent to the front surface and an option to use part of the rear surface for additional collection. The double collecting structures that can be made in this way are expected to show an increased short circuit current. In this paper, a detailed comparison between single- and double-sided collecting structures is presented. By means of one- and two-dimensional (1-D and 2-D) simulations, a detailed description is presented of the physical behavior of the double collecting structures, where an increased short circuit current is accompanied by a decreased open circuit voltage. It is shown that for the material quality presently used in industry, an efficiency gain up to 0.4% absolute can be obtained by using part of the rear surface for additional collection.