White Light Bias IPCE Experiment

A white light bias experiment may be necessary when the intensity of the monochromated light is insufficient to overcome losses due to filling of trap states or spontaneous emission. The additional intensity from a constant background of 

Equipment modifications are needed for a white light bias (see optional equipment in Fig. 7.1). The experiment requires a low noise broadband DC illumination, while simultaneously illuminating the sample with chopped ( AC) monochromatic light. The waveform of the chopped monochromic light must be monitored to verify that the chopping speed is low enough for the sample response to reach steady state. The bias level should be set to 37 % of the expected j c [2-4]. 

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For the biased IPCE experiments, data processing is performed in the same manner as for unbiased experiments. Care should be taken to record the applied bias and label the data accordingly such that it is clear that the experiment was performed under bias conditions (see Fig. 7.3a labels). The same rationale should be applied to any measurements performed with a white light bias. 

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