Growth Of Perovskite Nanocrystals Research Articles

Effects of oleylamine concentration on the synthesis of formamidinium lead halide perovskite nanocrystals and physical-optical properties

Perovskite nanocrystals (PNCs) has been extensively interested owing to their distinctive properties for applications in optoelectronics and energy harvesting. The properties of these nanocrystals, including optical and energy characteristics, can be tuned by adjusting the particle size using different synthesis techniques. Among these, the ligand-assisted reprecipitation (LARP) method has become popular for its simplicity and scalability. Nevertheless, it is vital to understand that the growth of PNCs is extremely sensitive to the conditions of synthesis, highlighting the importance of recognizing the factors that limit the formation and properties of PNCs. In this study, PNCs based on formamidinium lead bromide (FAPbBr3) were synthesized via the LARP method under room temperature and ambient atmospheric conditions. The structures and optical properties, including photoluminescence lifetime, of PNCs with varying amounts of organic ligands were investigated. Transmission electron microscopy showed that high concentrations of organic ligands lead to the formation of perovskite clusters. We also noted a slight red shift in the photoluminescence peak as the size of the PNCs increased. A peak photoluminescence quantum yield (PLQY) of 74% was achieved. This study provides crucial insights into the effects of ligand ratios and serves as a valuable resource for refining the synthesis parameters of PNCs.

High Color-Purity and Efficient Pure-Blue Perovskite Light-Emitting Diodes Based on Strongly Confined Monodispersed Quantum Dots.

Here, we develop an in situ photoluminescence (PL) system to monitor the nucleation and growth of perovskite nanocrystals and control the monomer supply rate to achieve strongly confined and monodispersed quantum dots (QDs) with average size of 3.4 nm. Pure-blue (460 nm wavelength) CsPbBr3 QDs with near unity PL quantum yield and narrow size distribution (small size dispersion of 9.6%) were thus produced. Light-emitting diodes (LEDs) based on these QDs were prepared by using an all-solution processing route, which showed narrow electroluminescence with full width at half-maximum of 20 nm and a high color purity of 97.3%. The device also had a high external quantum efficiency of 10.1%, maximum luminance of 11 610 cd m-2, and continuous operation lifetime of 21 h at the initial luminance of 102 cd m-2, corresponding to the state-of-art for pure-blue perovskite LEDs.

Enhanced thermal stability of MAPbBr3 nanocrystals by ligand modification

The intrinsic water and thermal instabilities of perovskite nanocrystals (PNCs) are considered to be a major obstacle hindering their wide potential applications in optoelectronic devices. Herein, we report the enhanced stability of MAPbBr3 (MA=methylammonium) PNCs by ligand modification of 3,3-diphenylpropylamine (DPPA) and octylamine bromide (OABr). The resultant MAPbBr3@PVDF (polyvinylidene fluoride) films could maintain 77.8% and 81.2% of original photoluminescence quantum yield (PL QY, 85.9%) once keeping at 60 ℃ and immersing in water for 7 days, respectively. The enhanced thermal stability could be mainly attributed to two situations. One is the introduced DPPA ligand, which can passivate the surface defects with large steric resistance to suppress the further growth of PNCs during heating. The other is the added OABr, which can not only coordinate to both surface cations and anions of PNCs, but also make the effective compensation of Br– vacancies stabilize the target MAPbBr3 PNCs.

Growth of perovskite nanocrystals in poly-tetra fluoroethylene based microsystem: on-line and off-line measurements

Cesium lead halide perovskite nanocrystals are photoelectric nanomaterials that have potential applications in a variety of areas due to their excellent photoelectric and tunable photo luminescent properties. In this work, we investigate the synergetic effects of reaction temperature, reaction-capillary length and flow rate on the growth kinetics of perovskite nanocrystals in a PTFE-based microsystem and the photoluminescence characteristics of the perovskite nanocrystals both on-line and off-line. The on-line measurement finds that increasing the reaction temperature leads to the increase of the wavelength of the PL emission peak of the synthesized nanocrystals and reduces the average size of the perovskite nanocrystals synthesized in long reaction-capillaries. The intensity of the PL emission peak of the nanocrystals synthesized at different reaction temperatures decreases with the increase of the flow rate. The off-line measurement reveals that increasing the flow rate generally leads to the blueshift of the PL emission peaks and the decrease of the average size of the perovskite nanocrystals synthesized at the reaction temperature of 160 °C in the capillary length of 60 cm. Increasing temperature leads to the increase of the emission wavelength of the perovskite nanocrystals from 560 to 608 nm. The temperature dependence of the average size of the synthesized nanocrystals with the same synthesis conditions at different temperatures can be described by the Arrhenius relationship with an activation energy of 8.54 kJ mol−1. Five different cross-sections of the synthesized perovskite nanocrystals are observed, including rhombus, hexagon, rectangle, square and quadrangle with three of them being observed for the first time.

Precursor solution volume-dependent ligand-assisted synthesis of CH3NH3PbBr3 perovskite nanocrystals

Ligand-assisted reprecipitation (LARP) technique is a powerful approach for the synthesis of organometal halide perovskite nanocrystals (PNCs). The morphology and surface property of the formed PNCs which determine their optical properties are ultrasensitive to the synthetic parameters. To guarantee the batch-to-batch reproducibility of PNCs with excellent optical properties, it is of central importance to better understand the factors influencing the formation of PNCs during LARP process. Herein the dual-factor of the amount of perovskite precursor and the polarity of mixture solvent was modified by varying precursor solution volume (PSV) in the LARP system. The concentration, size, surface state and optical properties of the synthesized CH3NH3PbBr3 PNCs as a function of PSV were systematically investigated aiming to understand the influence of the dual-factor on the nucleation and growth of PNCs. Experimental results revealed that few crystal nuclei was generated due to lower amount of precursor at lower PSV, which was favorable for the growth of large perovskite crystals. At the higher PSV, the inhibition of crystal growth with increased amount of precursor was compensated by increasing the polarity of mixture solvent, which led to the dissolution of surface ligands and eventually growth of large perovskite crystals. The obtained results on PSV-dependent synthesis of PNCs will be used as a guide to optimize the synthetic parameters in the LARP process.