Coordinated electrical characterization system for photovoltaic devices

We report the development of a coordinated electrical characterization station integrating the data collection and analysis of a wide variety of DC, AC, and transient measurements. The DC current-voltage measurements consider the overall carrier-transport characteristics and cell performance. The AC measurements (e.g., capacitance-voltage, admittance spectroscopy, drive-level capacitance profiling) provide information regarding the spatial distribution and exchange of charge carriers with traps. The transient measurements (e.g., open-circuit voltage decay) investigate the lifetime and recombination of non-equilibrium carriers in a cell. We demonstrate that a coordinated characterization including the DC, AC, and transient measurements may generate new insight and unique understanding of the photovoltaic device. Using the equivalent-circuit parameters determined from the coordinated characterization set, we simulated the decay behavior of the open-circuit voltage in a crystalline silicon solar cell and found good agreement with experiment. The coordinated electrical characterization of CdTe thin-film solar cells not only avoided a misinterpretation of the admittance spectroscopy data, but also provided information to estimate the electrically active thickness, photoconductivity, and mobility of the CdTe absorber.