Ultrathin self-supporting crystalline silicon solar cells with light trapping

An increase in efficiency as well as cost reduction can be achieved by reducing the base thickness of crystalline silicon solar cells. For this purpose an ultrathin crystalline silicon solar cell structure of the inversion layer type without a supporting substrate is introduced. The rear side is made up by a system of narrow elevated regions, upon which the majority carrier collecting ohmic contacts are located. No back surface field is applied. Light trapping provided by surface texturing and back surface reflector is included and its effect on the short circuit current is experimentally verified as a function of cell thickness and base doping. By simple mechanical means the active silicon thickness could be reduced down to 20 μm whilst, for the sake of a high production yield, excellent mechanical stability is maintained. These are the thinnest self-supporting crystalline silicon solar cells developed to date. Spectral response data are discussed with respect to light trapping