Synergistic interaction of multi-functional additives at the buried interface for efficient blue perovskite light-emitting diodes

Perovskite light-emitting diodes (PeLEDs) have emerged as a prominent area of research in recent years, owing to their promising prospects for application in solid-state lighting and high-resolution displays. High performance has been achieved in the green and red emissions. However, blue PeLEDs, which are critical for display applications, are less efficient. The interfacial problem between the perovskite emission layer and the charge injection layer significantly hinders the device performance. Here, we introduced l-aspartic acid potassium (PLAK) into the hole injection layer, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). The amino and carboxyl groups as well as potassium ions in the additive not only improved the wettability of PEDOT:PSS but also increased the nucleation sites at the interface, which simultaneously improved the film morphology and crystallinity, and fully passivated the bottom interface of the perovskite. In addition, the introduction of PLAK reduced the release of indium from ITO induced by acid PEDOT:PSS, thereby further inhibiting exciton quenching in the perovskite layer. Moreover, it achieved a better band alignment and successfully reduced the turn-on voltage of PeLEDs from 3.2 V to 2.9 V. Finally, the prepared blue PeLEDs emitted at 484 nm with the external quantum efficiency doubled from 3.23% to 6.98%. Our approach provides an effective strategy of buried interface engineering for improving the performance of blue PeLEDs. The synergistic effect of the doping strategy of basic amino acid salts at the interface enables the simultaneous modification of PEDOT:PSS and the bottom interface of the perovskite film to achieve efficient sky-blue PeLEDs.