Constructive Electroluminescence Interference for Ultra‐Efficient and Narrowband Perovskite‐Organic Tandem LEDs

The integration of solution-processed perovskite light-emitting diodes (PeLEDs) with vacuum-deposited organic light-emitting diodes (OLEDs) in tandem architectures offers a promising pathway toward next-generation displays. However, directly stacking electroluminescent units with dissimilar optoelectronic characteristics often results in electroluminescence losses and spectral broadening. To achieve efficient and narrowband tandem emission, we first develop high-performance green PeLEDs as the bottom subunit through rational trap-state management. By precisely optimizing device efficiency-impedance matching, we realize synchronous operation of the PeLED and OLED subunits at their respective maximum efficiencies, producing constructive electroluminescence interference and yielding significant efficiency enhancement. Moreover, delicate regulation of the relative emission contributions ensures optimal spectral overlap and superposition, leading to markedly strengthened narrowband output. Using this strategy, tandem devices integrating PeLEDs with two representative OLEDs deliver record-breaking external quantum efficiencies of 52.3% and 54.8%, with narrow full widths at half maximum of 22 and 24 nm, respectively. This work establishes a fundamental design principle for tandem light-emitting diodes that simultaneously overcome limitations in EL efficiency and color purity in advanced display technologies.