Low-dimensional phase suppression and defect passivation of quasi-2D perovskites for efficient electroluminescence and low-threshold amplified spontaneous emission

• Published in: Nanoscale 2022-01, Vol.14 (3), p.919-929
• Main Authors: Jin, Guangrong, Liu, Tanghao, Li, Yuanzhao, Zhou, Jiadong, Zhang, Dengliang, Pang, Peiyuan, Ye, Ziqing, Xing, Zhaohui, Xing, Guichuang, Chen, Jiangshan, Ma, Dongge
• Format: Article
• Language: English
• Subjects: Amplification; Crystal defects; Crystal structure; Density; Electroluminescence; Energy transfer; Excitons; Laser applications; Light emission; Light emitting diodes; Metal halides; Metal sheets; Perovskites; Phase distribution; Phases; Photoluminescence; Quantum confinement; Quantum efficiency; Spontaneous emission; Thiocyanates
• ISSN: 2040-3364; 2040-3372
• DOI: 10.1039/d1nr06549a

Quasi-2D metal halide perovskites are promising candidates for light-emitting applications owing to their large exciton binding energy and strong quantum confinement effect. Usually, quasi-2D perovskites are composed of multiple phases with various numbers of layers ( n ) of metal halide octahedron sheets, enabling light emission from the lowest-bandgap phase by cascade energy transfer. However, the energy transfer processes are extremely sensitive to the phase distribution and trap density in the quasi-2D perovskite films, and the insufficient energy transfer between different- n phases and the defect-induced traps would result in nonradiative losses. Here, significantly reduced nonradiative losses in the quasi-2D perovskite films are achieved by tailoring the low-dimensional phase components and lowering the density of trap states. Butylammonium bromide (BABr) and potassium thiocyanate (KSCN) are employed to synergistically decrease the nonradiative recombination in the quasi-2D perovskite films of PEABr : CsPbBr 3 . The incorporation of BABr is found to suppress the formation of the n = 1 phase, while adding KSCN can further reduce the low- n phases, passivate the notorious defects and improve the alignment of the high- n phases. By incorporating appropriate contents of BABr and KSCN, the resultant quasi-2D perovskite films show high photoluminescence quantum yield (PLQY) and highly ordered crystal orientation, which enable not only the green light-emitting diodes (LEDs) with a high external quantum efficiency (EQE) of 16.3%, but also the amplified spontaneous emission (ASE) with a low threshold of 2.6 μJ cm −2 . These findings provide a simple and effective strategy to develop high-quality quasi-2D perovskites for LED and laser applications. Synergistically tailoring phase components and reducing trap density enable quasi-2D perovskites to achieve light-emitting diodes (LEDs) with high efficiency and amplified spontaneous emission (ASE) with low threshold.