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The WCT-100 photoconductance instrument is used throughout the photovoltaic industry providing a relatively simple and inexpensive means to assess recombination parameters. This paper presents a method to determine its output voltage V WCT over the conductance range, S ¼ 0Á002-20 mS, a range not easily attained by the conventional calibration method. The relationship between V WCT and S is found to transition from being non-linear to linear at S $ 1 mS, which equates to the conductance of a 300 mm thick 30 V-cm silicon wafer. For samples whose dark conductance is lower than the transition conductance, the non-linear relationship between V WCT and S must be taken into account to prevent a gross underestimation of recombination rate. The method we describe can equally well be used to investigate the calibration of other photoconductance instruments. It involves the simultaneous measurement of a device's electrical conductance and the instrument's output voltage under a range of steady-state illumination intensities.

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