Impedance spectroscopy of Au/Cu2Te/CdTe/CdS/Cd2SnO4/glass solar cells

Abstract

In this work, we report impedance spectroscopy (IS) study on CdS/CdTe-based solar cells. The physical parameters of the cell were computed in the dynamic regime to access to the information on different capacitive, resistive processes, and characteristic response times occurring inside the device. Cell parameters as the depletion width, build-in voltage, diffusion length, minority carrier lifetime, among others, were calculated from IS measurements. The impedance spectra were fitted with an equivalent circuit containing a constant phase element and two resistances, one in series and the other one in parallel. These elements address the underlying physical parameters of the device and adequately describe its global response. The cell parameters calculated from IS were used in a numerical approach that considers: i) the spectral irradiance at AM1.5, ii) the experimental transmittance of our conductive Cd2SnO4, iii) the reflectance of the solar cell stack, and iv) the CdS and CdTe absorption coefficients to obtain the spectral response and the short-circuit current density Jsc of the cell. Finally, the calculated Jsc along with the series and parallel resistances were used to obtain a calculated J-V characteristic curve and this was compared with the experimental curve showing good agreement.