Electrical characterization of mobile ions in perovskite solar cells
In recent years, solar cells based on metal-halide perovskites have attracted significant attention as promising candidates for next-generation solar cells due to their rapid rise in power conversion efficiency. However, their commercialization is still hindered by insufficient long-term stability. A central cause for this limited stability is the migration of mobile ions within the perovskite layer. These ions contribute to various loss mechanisms that reduce device performance. Specifically, their migration reduces key photovoltaic parameters such as short-circuit current density, open-circuit voltage, and fill factor, ultimately lowering the efficiency. To address this issue, accurate methods to quantify the properties of mobile ions are necessary.
In his thesis, Moritz Schmidt focuses on the development and application of electrical measurement techniques to study and quantify mobile ions in perovskite solar cells. By combining experimental measurements with drift-diffusion simulations, he shows how mobile ions impact observable electrical responses like the capacitance and the current of perovskite solar cells.
Schmidt focused on previously applied techniques such as current and capacitance transients or capacitance frequency measurements, but also developed a novel technique, called thermally activated ion current (TAIC) measurements. The theoretical understanding of the different techniques allows for the determination of key properties of mobile ions, such as their density, diffusion coefficient, and activation energy.
Overall, the results presented in this thesis offer a comprehensive theoretical understanding of mobile ions, facilitating their quantification. This quantification is a crucial step toward enhancing device stability and, ultimately, the commercialization of perovskite solar cells.