Characterize and Retard the Impact of the Bias‐Induced Mobile Ions in CH ₃ NH ₃ PbBr ₃ Perovskite Light‐Emitting Diodes

Abstract Herein, the aspects of ion migration in polycrystalline CH ₃ NH ₃ PbBr ₃ thin film and their phenomenal influences on the output performance of perovskite light‐emitting diodes (PeLEDs) are reported. The physical insight of bias‐induced migration of mobile ions in the perovskite active layer effectuating the observed non‐linearity in the increased magnitude of electroluminescence (EL) and luminous efficiency (LE) as a function of current density for PeLEDs is directly evidenced using the capacitance spectroscopy. Adding the zwitterion molecule, Choline chloride (Ch.Cl), in CH ₃ NH ₃ PbBr ₃ precursor solution for preparing polycrystalline perovskite film effectively passivates the charged defects, either positively or negatively, in organic‐inorganic halide perovskite and most importantly interferes the migration of ions crossing the grains in PeLEDs as verified by the higher calculated magnitude of the activation energy for the migration of mobile ions. As a result, the Ch.Cl‐additive devices exhibit the rather stable EL and LE magnitude under the electric bias. EL magnitude increases linearly as a function of current density, revealing the epitome of output characteristics for decent light‐emitting diodes. To suppress the influence of the migrating ions on operating PeLEDs is a key issue before it is stepped further to advance the efficiencies and the operational stabilities of perovskite devices.