Two-Factor Phase Separations in Mixed-Halide Quasi-2D Perovskite LEDs: Dimensionality and Halide Segregations
Seok Joo Yang, Kang Wang, Yanqi Luo, Jee Yung Park, Hanjun Yang, Aidan H. Coffey, Ke Ma, Jiaonan Sun, Sarah Wieghold, Chenhui Zhu, Letian Dou
Abstract
Quasi-2D halide perovskites have attracted much interest as a promising material for light-emitting diodes (LEDs) due to their tunability in quantum confinement and halide alloy formation to modulate the energy bandgap and emission color. However, two-factor phase separations with respect to heterogeneous quantum-well thicknesses and halide segregation are still crucial issues in quasi-2D perovskite LEDs, leading to low external quantum efficiencies (EQEs) and color shifts. Herein, we compare quasi-2D perovskite films using different cations to unveil the key contributions from the chemical design of organic cations. While mixing halide ions in conventional quasi-2D perovskite films induces micrometer-scale heterogeneity, new extended and twisted conjugated cations suppress the two-factor phase separations, leading to high EQEs of over 25% and controllable emission wavelengths across red and near-infrared regions. The fundamental insights in this work will provide guidance for advancing materials design and device performance in the future.