Degradation free Si/sub O/2 passivation layer oxidized by TCA process

Degradation of the Si/SiO/sub 2/ interface in solar cells induced by sunlight irradiation can be eliminated by controlling the concentration of 1.1.1. trichloroethane (TCA) in the oxidation ambient. Despite the higher carbon concentration, the oxide which was grown 48 hours after the TCA cleaning showed no evident light degradation. A low interface trap density, D/sub it/, was obtained for this Si/SiO/sub 2/ interface. Bias light dependence of the surface recombination velocity for such degradation-free SiO/sub 2/ layers was intensively analyzed by measuring effective lifetimes. The mechanism that limits fill factors in recent high-efficiency one-sun solar cells is discussed quantitatively in terms of the dependence of the surface recombination velocities on excess carrier concentration. It was clarified that even with such a small D/sub it/, a high surface recombination velocity will result at the SiO/sub 2Si interface with the excess carrier concentration under Vop condition.<
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