Multilayer Capacitances: How Selective Contacts Affect Capacitance Measurements of Perovskite Solar Cells
Sandheep Ravishankar, Zhifa Liu, Uwe Rau, and Thomas Kirchartz
PRX Energy 1, 013003 – Published 7 April 2022
Capacitance methods, such as capacitance-voltage-frequency measurements, Mott-Schottky analysis, and thermal-admittance spectroscopy measurements, are powerful tools to obtain important parameters of the solar cell, such as doping and defect densities, built-in voltages, and activation energies.
However, the validity of these analyses assumes that the capacitance response originates solely from the absorber layer.
Here, the authors demonstrate that this assumption is not valid for perovskite solar cells, since the thin and low-mobility selective-contact layers significantly contribute to the measured capacitance. Using a combination of drift-diffusion simulations and analytical modeling, they develop guidelines for the measurement of doping and defect densities, built-in voltages, and activation energies from these capacitance methods. These guidelines can be applied to any photovoltaic technology that incorporates low-conductivity charge-transport layers in addition to the absorber layer.