In recent years, perovskite nanocrystal superlattices have been reported with collective optical phenomena such as superfluorescence. The superlattices of perovskite nanoplates can be easily observed on electron microscopy grids, for example, and they too present ensemble optical response. However, little is known on the self-assembly and optical properties of the perovskite nanoplates superlattices in solvents. Here, we report on the condition for this selfassembly to occur and show a simple strategy to induce the formation of these nanoplates stacks in suspension in different organic solvents. We combined wide- and small angle Xray scattering and scanning transmission electron microscopy to evaluate CsPbBr3 and CsPbI3 perovskite nanoplates with different thickness distributions. We observed the formation of these stacks by changing the concentration and viscosity of the colloidal suspensions, without the need of antisolvent addition. We found that, in hexane, the concentration threshold for the formation of the stacks is rather high and approximately 80 mg/mL. In contrast, in decane, dodecane, and hexadecane, we observe a much easier formation of these stacks: the higher is the viscosity, the easier is the stacking of the nanoplates. We, then, discuss the impact of the proximity of the perovskite nanoplates in their colloidal stacks or solid superlattices in terms of Förster resonant energy transfer. Our predictions suggest an energy transfer efficiency higher than 50%, even in a low photoluminescence quantum yield scenario, for both perovskite compositions.

In recent years, perovskite nanocrystal superlattices have been reported with collective optical phenomena, offering a promising platform for both fundamental science studies and device engineering. In this same avenue, superlattices of perovskite nanoplates can be easily prepared on different substrates, and they too present ensemble optical response. However, the self-assembly and optical properties of these aggregates in solvents have not been reported to date. Here, we report on the condition for this self-assembly to occur and show a simple strategy to induce the formation of these nanoplates stacks in suspension in different organic solvents. We combined wide- and small-angle X-ray scattering and scanning transmission electron microscopy to evaluate CsPbBr3 and CsPbI3 perovskite nanoplates with different thickness distributions. We observed the formation of these stacks by changing the concentration of nanoplates and the viscosity of the colloidal suspensions, without the need of antisolvent addition. We found that, in hexane, the concentration threshold for the formation of the stacks is rather high and approximately 80 mg/mL. In contrast, in decane, dodecane, and hexadecane, we observe a much easier self-assembly of the nanoplates, presenting a clear correlation between the degree of aggregation and viscosity. We, then, discuss the impact of the self-assembly of perovskite nanoplates on Förster resonant energy transfer. Our predictions suggest an energy transfer efficiency higher than 50%, even in a low photoluminescence quantum yield scenario, for both perovskite compositions.

In recent years, perovskite nanocrystal superlattices have been reported with collective optical and electronic quantum phenomena. Regarding perovskite nanoplates, their superlattices can be easily observed on electron microscopy grids, for example, and they too present ensemble optical response. However, little is known on the self-assemble and optical properties of the perovskite nanoplates superlattices in solvents. Here, we report a simple strategy to induce the formation of these nanoplates stacks (1D superlattices) in suspension in different organic solvents. We investigate the influence of concentration and viscosity on their formation. For that purpose, we combined wide- and small-angle X-ray scattering and scanning transmission electron microscopy to evaluate CsPbBr3 and CsPbI3 perovskite nanoplates with different thickness distributions. We found that, in hexane, the concentration threshold for the formation of the aggregated stacks is rather high and approximately 80 mg/mL. In contrast, in decane, dodecane, and hexadecane, we observe a much easier formation of these stacks: the higher is the viscosity, the easier is the stacking of the nanoplates. We, then, discuss the impact of the proximity of the perovskite nanoplates in their colloidal stacks or solid superlattices in terms of Föster resonant energy transfer. We predict an efficiency higher than 50% in the energy transfer even in a low photoluminescence quantum yield scenario for both perovskite compositions.