Modulations of Quasi-Two-Dimensional Metal Halide Perovskites toward High-Performance Blue Light-Emitting Diodes

Quasi-two-dimensional (quasi-2D) perovskites are promising candidates for blue light-emitting diodes (LEDs) because of their combined quantum- and dielectric-confinement effects. By judiciously controlling the material components and phase distributions, it is more feasible to modulate the wavelength of quasi-2D perovskite emitters to desired pure-blue emission for display applications compared with the widely investigated mixed-halide 3D perovskites and colloidal quantum dots with ultra-small sizes. Employing quasi-2D perovskites is also advantageous in circumventing the severe phase separation in blue mixed-halide perovskites with elevated chlorine ratios and fragile surface properties of quantum dots. During the past several years, extensive efforts have been devoted to optimizing the film properties of blue quasi-2D perovskite and device engineering of corresponding LEDs, enabling rapid progress in the device performance. This review first introduces fundamental structural and photophysical properties of quasi-2D perovskite materials, and comprehensively summarizes strategies for modulating the blue quasi-2D perovskite films. The review focuses on the key phase modulation related to the materials and interface engineering, as well as the perovskite film manufacturing process. Then, the remaining challenges on blue LEDs based on quasi-2D perovskites are discussed, and finally perspectives on desired efforts on the materials and interfacial contacts toward further performance improvements are provided.