Minority Carrier Lifetime Measurement in HF Solution to Evaluate Si Substrates for Solar Cells

Minority carrier lifetime measurement using a microwave photoconductivity decay method was examined. A simple method of immersing a silicon wafer in a toxic HF solution by using a plastic envelope is introduced. An effective lifetime in 50% HF solution is much higher than that in air due to reduction of the surface recombination velocity and is almost the same compared with that of an oxidized and well-passivated substrate. This method provides the effective lifetime, which approximates a bulk lifetime, without an oxide layer and is useful in estimating the short circuit current of solar cells prior to the cell fabrication.