Measurement of differential and actual recombination parameters on crystalline silicon wafers [solar cells]

In this paper, for the first time, measurements of differential and actual recombination parameters on crystalline silicon wafers are directly compared. In order to determine the differential bulk lifetime and the differential surface recombination velocity (SRV), small-signal light-biased microwave-detected photoconductance decay (MW-PCD) and modulated free-carrier absorption (MFCA) measurements are performed. The results obtained by these widespread techniques are compared with quasi-steady-state photoconductance (QSSPC) measurements, which directly determine the actual recombination parameters. On high-resistivity (1000 Ωcm) float-zone (FZ) n-type silicon at high injection levels, it is shown that the differentially measured Auger lifetime is a factor of three smaller than the actual Auger lifetime. This finding is in excellent agreement with the theory derived in this work. Thermally oxidized low-resistivity (~1 Ωcm) p-Si wafers serve as an experimental vehicle to compare the differential and the actual injection-level dependent SRV of the Si-SiO₂ interface under low-injection conditions. Using two different integration procedures, the actual SRV is calculated from the differentially measured quantity. The actual SRV measured by the QSSPC technique is found to match perfectly the actual SRV obtained by integration