Physical limitations for homogeneous and highly doped n-type emitter monocrystalline silicon solar cells

Homogeneous emitter solar cells with Gaussian profiles have been optimized based on a one-dimensional theoretical model with analytical solutions. A complete n(+)pp(+) structure was optimized considering the shadowing factor F-m congruent to 3%, typical for laboratory processes. The studies demonstrate the high quality of the homogeneous emitters, presenting high emitter collection efficiencies and low recombination current densities. Since the fabrication technology for these emitters is simple, their physical limitations in industrial processes are analyzed, showing that Ag screen printing (typical for industrial cell contacts), requires Gaussian profile emitters with a surface doping level greater than N-s = 1 X 10(20) cm(-3) in order to minimize the metal-semiconductor contact resistance. A comparison between the electrical output parameters of homogeneous emitter silicon solar cells with shadowing factors F-m congruent to 3% and F-m congruent to 7% has been made. A decrease of congruent to2.5% in the solar cell maximum efficiency was found when the shadowing factor was increased and the industrial requirements were satisfied. However, if new technologies that allow selective or non-homogeneous emitters are considered, efficiencies up to congruent to20% may be reached, being only 1.6% lower than the optimized laboratory solar cells. (C) 2003 Elsevier Ltd. All rights reserved.