Contactless Measurement of Pico-to-Nanosecond Dynamics of Photovoltage: its Utility and Constraint

A contactless measurement of the picosecond dynamics of photovoltage in two GaAs solar cells, one with n-layer on the top and the other with p-layer, was performed using time-resolved photoemission spectroscopy. We found that the shift of photoelectron spectra occurs in opposite directions for the two samples. This agrees with the interpretation that the spectral shift is caused by photovoltage at the p-n junction. We also summarize the limiting factors on the present technique including the degradation of the temporal resolution caused by propagation effect, and the deformation of spectra originating from the work-function cutoff, and discuss the possible solutions.