Perovskite light-emitting diodes with low roll-off efficiency via interfacial ionic immobilization

Metal halide perovskite light-emitting diodes (PeLEDs) are emerging low-cost solution-pmcessable technology with high color purity and tunable emission wavelength. However, the defective interface between pemvskite emission layer and charge transport layer substantially limits the improvement of device performance, especially for a device with simultaneously high luminance and decent external quantum efficiency. Herein, we propose a facile and reliable interfacial modification strategy to realize efficient PeLEDs with high external quantum efficiency under high luminance. By modifying the hole transport layer with alkali metal ions (K+, Na+) and weak acid ion (citrate ion), perovskite films with high surface coverage and fewer interface defects are fabricated. As a result, a high brightness of 80,288 cd/m(2) and a high external quantum efficiency of 13.02% under continuous current drive are obtained in our PeLEDs. More commendable, our devices show low roll-off behaviors of EQE under high luminance and high current density, because of halide anion and lead cation vacancies at the interface of perovskite and charge transport layer are efficiently suppressed.