Guidelines for more accurate determination and interpretation of effective lifetime from measured quasi-steady-state photoconductance

This paper clarifies three measures that should be taken to more accurately calculate and interpret the effective lifetime (τeff) from quasi-steady-state photoconductance: 1) In order to account for the dependence of photogeneration on the illuminating spectrum and the test wafer reflectance, the correct value is assigned to the effective optical transmission. 2) In order to account for the dependence on the illuminating spectrum of the constant of proportionality between the short-circuit current of the reference cell and the total photon flux, we introduce a spectral correction factor. 3) Once the correct value of τeff has thus been found, the solution to the time-dependent continuity equation is applied to assess the error in the commonly used expression 1/τeff = 1/τb + 2S/W, relating τeff, bulk lifetime (τb), and surface recombination velocity (S). An example illustrates that ignoring these three guidelines can cause S to be underestimated by over 40%.