LARGE AREA AND SCREEN PRINTED N-TYPE SILICON SOLAR CELLS WITH EFFICIENCY EXCEEDING 18%.

Abstract

There is currently much interest in n-type base solar cells because of potential advantages, both of silicon base material and of cell process, for high efficiency. We present results of n-base solar cells on large area multicrystalline and monocrystalline silicon wafers, produced using simultaneous diffusion of phosphorus back surface field and boron emitter, screen-printed metallization and firing through. The cell process leads to record high efficiencies of 16.4% on multicrystalline and 18.3% on monocrystalline wafers. It is experimentally demonstrated that in multi-crystalline Si a low resistivity is correlated to reduced cell efficiency, with the optimum base resistivity lying between 1.5 and 4 Ωcm. By characterizing and modeling cells from monocrystalline Si, from nominally clean multicrystalline Si, as well as from intentionally Fe-contaminated multi- crystalline Si, the impact of purity on emitter recombination is investigated in more detail. Keywords: Boron, n-type, Silicon Solar Cell.