IMPEDANCE SPECTROSCOPY AND EQUIVALENT CIRCUITS OF HETEROJUNCTION SOLAR CELL BASED ON n-Si/POLYANILINE BASE'

摘要

Different equivalent circuit models were used to fit the impedance spectra of a novel polyaniline base (EB)-type Si heterojunction solar cell at different bias voltages. The photovoltaic cell characteristics, i.e., open circuit voltage (V_(OC)), short circuit current density (J_(SC)), factor (FF) and energy conversion efficiency (η) were evaluated underillumination (0.09 W/cm~2) to be are 5.1 mA/cm~2, 214 mV and 0.974%, respectively Rollover and crossover phenomena in current density-voltage (J- V) curves under illumination were explained based on back contact barrier and the surface recombination of electrons at back contact. A phenomenological description of the capacitance behaviour was obtained by replacing the capacitor of the first model by a frequency-dependent non-ideal capacitor, a so-called constant phase element (CPE). The impedance spectra obtained at different applied voltages under illumination was not fitted with the same equivalent circuit as reported under darkness. The spectra displayed a phenomenon of negative imaginary impedance were related to the inductive effect in low frequencies in the heterojunction.