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Room-temperature luminescence diagnostics in polycrystalline silicon

Improvement of recombination properties is observed in EFG microcrystalline Si wafers subjected to consecutive solar cell processing steps. A dramatic increase of room- temperature band-to-band photoluminescence (PL) intensity (hvmax equals 1.1 eV) by a factor of two orders of magnitude occurs in the solar cell, to demonstrate a significant reduction in non-radiative recombination during the upgrading steps that benefit solar cell efficiency. Using spatially resolved PL mapping over 100 cm2 wafers, we study PL behavior in solar cell fabrication. We compared point-by-point PL mapping with distribution of minority carrier diffusion length in the same poly-Si wafer. A correlation between PL intensity and the diffusion length is documented using a statistically valid data-base. It is suggested that room-temperature PL mapping can be used for on-line monitoring of poly-Si solar cell quality.