Ionic Transport in Perovskite Light-Emitting Electrochemical Cells and Performance Dynamics

We studied the ionic defect transport and performance dynamics of Perovskite Light-Emitting Electrochemical Cells with impedance spectroscopy and lifetime measurements. Utilizing additive ions from salts such as LiPF6 in our devices increases efficiency and lifetime. We posit that the additive ions are more mobile via a lower barrier of diffusion energy and allow the intrinsic perovskite ions to remain intact more so than without the additive ions serving as sacrificial ions that accumulate at the interfaces to produce p-type and n-type regions at the injection interfaces under electrical bias. The eventual degradation in performance is studied and is thought to be an over accumulation of ionic defects at the interface and a reduction in an optimal radiative recombination region or an unbalanced concentration of electronic charge carriers. Using Warburg diffusion impedance elements, we are able to extract the diffusion coefficients and concentrations of multiple ionic species within the perovskite layer. Using temperature dependent measurements we're able to extract diffusion barrier energies and enthalpies of formation. Diffusion elements are used in equivalent circuit models for fitting impedance spectroscopy measurements with good fits and low error of fitting parameters.