SiO2-passivated high efficiency silicon solar cells - process dependence of Si-SiO2 interface recombination

In comparison of simultaneously processed MOS test structures and solar cells the effect of variing postmetallization annealing time and temperature, oxidation temperature and ambient as well as the surface morphology is investigated. More than 20 min at 400 degree C are found as the optimum postmetallization annealing conditions. No significant effect of oxidation temperature variations between 950 and 1100 degree C is observed. For all oxidation temperatures an equally strong increase of the recombination velocity at the passivated rear surface with excess carrier concentration is found. Using measured MOS data and an extended SRH recombination formalism in an elaborate description of the surface space charge layer this dependence can be understood quantitatively.