Efficient quasi-2D-structure perovskite light-emitting diodes (4.90 cd A(-1) ) are demonstrated by mixing a 3D-structured perovskite material (methyl ammonium lead bromide) and a 2D-structured perovskite material (phenylethyl ammonium lead bromide), which can be ascribed to better film uniformity, enhanced exciton confinement, and reduced trap density.

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Outstanding material properties of organic-inorganic hybrid perovskites have triggered a new research insight into the next-generation solar cells. Moreover, a wide range of controllable properties of hybrid perovskites particularly depending on crystal growth conditions enables versatile high performance optoelectronic devices such as light-emitting diodes, photodetectors and lasers beyond solar cells. This invited review article highlights recent progress of the crystallization strategies of organic-inorganic hybrid perovskites for effective light harvester or light emitter. In the first part, fundamental background on the perovskite crystalline structures and relevant optoelectronic properties such as optical band-gap, electron-hole behavior and energy band alignment are introduced. In the second part, detailed overview of the effective crystallization methods for perovskites, including thermal treatment, additives, solvent mediator, laser irradiation, nanostructure, crystal dimensionality and so on, is described to offer a comprehensive correlation among perovskite processing conditions, crystalline morphology and relevant device performances. Finally, future research direction is proposed to overcome current practical bottlenecks and move towards reliable high performance perovskite optoelectronic applications.3

Owing to unique potential for high color purity luminance based on low-cost solution processes, organic/inorganic hybrid perovskite light-emitting diodes (PeLEDs) are attracting a great deal of research attention. For high performance PeLEDs, optimum control of the perovskite film morphology is a critical parameter. Here, we introduce a reliable and well-controllable PeLED crystallization process based on beam-damage-free near-infrared laser (λ = 808 nm) irradiation. Morphology of the CHNHPbBr films can be precisely controlled by laser irradiation condition parameters: power density and beam scan rate. We systematically investigate the perovskite film morphology and device performance of the PeLEDs under different processing conditions. In the optimum power density and high beam scan rate (30 W cm, 0.1 mm s), a dense and smooth perovskite film is attained with a small crystal grain size. The critical relationship between the crystal grain size and LED efficiency is established while attaining the device performance of 0.95 cd A efficiency and 1784 cd m.

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