Quantification of ion migration in CH3NH3PbI3 perovskite solar cells by transient capacitance measurements

Abstract

We quantify activation energy, concentration, and diffusion coefficient of mobile ions in MAPbI ₃ perovskite solar cells using transient ion-drift measurements.

Abstract

Ion migration in halide perovskite films leads to device degradation and impedes large scale commercial applications. We use transient ion-drift measurements to quantify activation energy, diffusion coefficient, and concentration of mobile ions in methylammonium lead triiodide (MAPbI ₃) perovskite solar cells, and find that their properties change close to the tetragonal-to-orthorhombic phase transition temperature. We identify three migrating ion species which we attribute to the migration of iodide (I ⁻) and methylammonium (MA ⁺). We find that the concentration of mobile MA ⁺ ions is one order of magnitude higher than the one of mobile I ⁻ ions, and that the diffusion coefficient of mobile MA ⁺ ions is three orders of magnitude lower than the one for mobile I ⁻ ions in our samples. This quantification of mobile ions in MAPbI ₃ will lead to a better understanding of ion migration and its role in operation and degradation of perovskite solar cells.