High-Performance Quasi-2D Perovskite LEDs Enabled by a Multifunctional Small Molecular Additive

Quasi-two-dimensional (quasi-2D) perovskites have emerged as promising emitters for high-performance light-emitting diodes owing to their superior excitonic properties and high photoluminescence quantum yields. However, inefficient energy funneling arising from the unfavorable distribution of multidimensional phases and abundant defect states remains a major obstacle to achieving highly efficient electroluminescence. Herein, 2-bromodibenzothiophene (BDBT) is introduced as a multifunctional additive to simultaneously regulate phase distribution and suppress defect-assisted non-radiative recombination in quasi-2D perovskite films. The incorporation of BDBT modulates the interaction between organic spacer cations and the perovskite framework, promoting more efficient energy transfer among different-dimensional domains. Meanwhile, the sulfur-containing Lewis base in BDBT effectively coordinates with undercoordinated Pb2+ ions, passivating trap states and reducing non-radiative losses. As a result, the optimized quasi-2D perovskite light-emitting diodes exhibit a peak external quantum efficiency of 19.2% at 515 nm and a maximum luminance exceeding 6500 cd m-2. This work provides an effective molecular engineering strategy for simultaneously optimizing energy transfer and defect passivation, offering new insights into the development of highly efficient quasi-2D perovskite light-emitting devices.