Step scan time resolved spectroscopy and its application to photoconductivity of Si solar cells*

We report on the establishment of Fourier transform step-scan time-resolved photoconductivity spectroscopy to study the solar cell's minority carrier lifetime ,which has close relationship with its conversion efficiency.Three typical Si so lar cells are selected in our experiments,including both the monocrystalline and polycrystalline silicon samples.We find that the rise and decay curves of the t ransient photoconductivity can be well described by two simple exponential funct ions.Due to the participation of recombination centers,the recombination minorit y carrier lifetimes are generally smaller than those of generation.In order to p rove the reliability of our experimental results,we extract the bulk lifetime an d the effective diffusion length of the three samples.Furthermore,we analyze the correlation of the minority lifetime with the shortcircuit current,open volta ge and conversion efficiency,by the aid of the investigation of solar cells' dark I-V characteristics and load characteristics.In addition,we also discuss in detail other applications of the established stepscan time-resolved spect roscopy.