Characterization of solar cells by frequency-domain transient analysis

The FDTA (frequency-domain transient analysis) technique is applied to extract base transport parameters in a back-surface field silicon solar cell. FDTA relies upon two separate experiments, one for uniformly absorbed light and one for strongly absorbed light. The time-domain short-circuit current responses of the two forms of excitation are captured by a digitizing oscilloscope and then Fourier-transformed. The frequency response may be related to analytical expressions for the short-circuit current. By optimizing the agreement between experimental and analytic spectra, values for the minority-carrier lifetime and diffusion coefficient and the back-surface recombination velocity are obtained. The results obtained at 23 degrees C for a 12.5 Omega -cm n⁺-p cell with a base thickness of 300 mu m are: tau _n=50 mu s, D_n=36.6 cm²/s, S<5 cm/s, and L_n=(D_n tau _n)¹2/=428 mu m.