Ion Motion Determines Multiphase Performance Dynamics of Perovskite LEDs

Perovskite light-emitting diodes (PeLEDs) currently reach up to about 20% external quantum efficiency (EQE) and are becoming a promising technology for display and lighting applications. Still, many issues regarding their performance remain unresolved, particularly those related to stability, operation in non-stationary regimes, and efficiency roll-off at high current densities. Here, some of those issues in PeLEDs based on MAPbI(3) perovskite are addressed. The authors analyze the electroluminescence (EL) and current dynamics after the first-time voltage application and after application of sequences of voltage pulses, at different temperatures. Analysis of the results suggests that the complex dynamics observed on time scales from sub-seconds to minutes and hours can be explained by the spatial redistribution of mobile species, most likely iodine interstitials, characterized by approximate to 175 meV activation energy. This redistribution alters the carrier injection, spatial electric field, and charge carrier density distributions as well as density of nonradiative recombination centers within the perovskite layer. Mathematical modeling of the ion motion and related processes enabled to reproduce the EL and current dynamics and to disentangle complex sequence of processes governing the PeLED operation.