Phosphonic acid based bifunctional additive for high-performance blue perovskite light-emitting diodes

Quasi-two-dimensional (quasi-2D) Ruddlesden-Popper (RP) phase perovskite materials exhibiting quantum confinement effect are promising candidates for realizing high-performance blue perovskite light-emitting diodes (PeLEDs). However, the performance of blue PeLEDs based on quasi-2D perovskites remains unsatisfactory, as it is limited by non-ideal charge transport, energy transfer, and defect. Here, a series of bifunctional phosphonic acid additives with synergistic effects are reported. These additives passivate defects and reduce non-radiative recombination losses by coordinating P=O functional group with unsaturated Pb2+, and they promote energy transfer and radiative recombination by optimizing the proportion of small n phases and large n phases. Owing to the synergistic effects of passivation and energy transfer, optimized blue PeLEDs (~486 nm) with 3-phosphonopropionic acid (3-PA) additive exhibits a champion EQE of 13.11%, which is exceptionally high for blue PeLEDs.