Recombination lifetimes in highly aluminum-doped silicon

Abstract

We show that the recombination lifetimes measured in highly aluminum-doped p-type silicon (Al-p+) regions, fabricated by means of screen printing and firing of aluminum paste, are three orders of magnitude larger than the lifetimes expected from the extrapolation of the lifetime data measured on aluminum-doped Czochralski-grown silicon wafers. Solar cell simulations demonstrate that the lifetime of 130 ns measured in Al-p+ regions with an aluminum doping concentration of ∼2×1018 cm−3 enables solar cell open-circuit voltages of 670 mV and energy conversion efficiencies of 21% on n-type silicon wafers. These results prove that the efficiency potential of screen-printed Al-p+ emitters for the application to rear-junction n-type silicon solar cells is much higher than traditionally assumed.