Coordinating Solvent-Assisted Synthesis of Phase-Stable Perovskite Nanocrystals with High Yield Production for Optoelectronic Applications

Inorganic perovskite nanocrystals (NCs) have shown good potential as an emerging semiconducting building block owing to their excellent optoelectronic properties. However, despite extensive studies on their structure-dependent optical properties, they still suffer severely from chemical and phase instabilities in ambient conditions. Here, we report a facile method for the synthesis of mixed halide inorganic perovskite NCs based on recrystallization in an antisolvent mixture in an ambient atmosphere, at room temperature. We introduced an alcohol-derivative solvent, as a secondary antisolvent in the solvent mixture, which crystallizes at room temperature. This mediates and facilitates the perovskite crystallization, leading to a high chemical yield and stability. We demonstrate that this secondary antisolvent establishes intermolecular interactions with lead halide salt, which successfully stabilizes the γ-dark phase of perovskite by encapsulating NCs in a solution and thin film. This allows us to produce concentrated NC solutions with a photoluminescence quantum yield of 70%. Finally, we fabricate CsPbI2Br NCs (optical bandgap 1.88 eV) solar cells, which showed a stabilized photovoltaic performance in ambient conditions, without encapsulation, showing a Voc of 1.32 V

Metal Coordination Sphere Deformation Induced Highly Stokes-Shifted, Ultra Broadband Emission in 2D Hybrid Lead-Bromide Perovskites and Investigation of Its Origin

Published studies of layered (2D) (100)-oriented hybrid lead-bromide perovskites evidence a correlation between increased inter-octahedral (Pb-Br-Pb) distortions and the appearance of broadband white light emission. However, the impact of distortions within their constituent [PbBr6]4- octahedra has yet to be assessed. Herein, we report two new (100)-oriented 2D Pb-Br perovskites, whose structures display unusually high intra-octahedral distortions, whilst retaining minimal inter-octahedral distortions. Using a combination of temperature-dependent, power-dependent and time-resolved photoluminescence spectroscopic measurements, we show that increased intra-octahedral distortion induces exciton localization processes and leads to formation of multiple photoinduced emissive colour centres. Ultimately, this leads to highly Stokes-shifted, ultrabroad white light emission at room temperature

Metal Coordination Sphere Deformation Induced Highly Stokes‐Shifted, Ultra Broadband Emission in 2D Hybrid Lead‐Bromide Perovskites and Investigation of Its Origin

Published studies of layered (2D) (100)-oriented hybrid lead-bromide perovskites evidence a correlation between increased inter-octahedral (Pb-Br-Pb) distortions and the appearance of broadband white light emission. However, the impact of distortions within their constituent [PbBr6]4- octahedra has yet to be assessed. Herein, we report two new (100)-oriented 2D Pb-Br perovskites, whose structures display unusually high intra-octahedral distortions, whilst retaining minimal inter-octahedral distortions. Using a combination of temperature-dependent, power-dependent and time-resolved photoluminescence spectroscopic measurements, we show that increased intra-octahedral distortion induces exciton localization processes and leads to formation of multiple photoinduced emissive colour centres. Ultimately, this leads to highly Stokes-shifted, ultrabroad white light emission at room temperature

Hyperbolic nanoparticles on substrate with separate optical scattering and absorption resonances:a dual function platform for SERS and thermoplasmonics

Abstract Tuning optical properties of plasmonic nanostructures, including their absorption, scattering, and local-field distribution is of great interest for various applications that rely on optical energy regulated by plasmonic effects. Conventional plasmonic nanostructures enhance light scattering and absorption simultaneously, leading to compromise for either surface-enhanced spectroscopy or thermoplasmonic applications. In this paper, a dual functional platform based on a hyperbolic meta particles (HMP) substrate that exhibits separate and tuneable wavelengths of absorption and scattering resonances for both thermoplasmonics and surface enhanced Raman spectroscopy (SERS), is demonstrated. Significantly, either light-to-heat conversion efficiency at the absorption resonance band or SERS performance at the scattering resonance band of the HMP substrate is improved in comparison to those of plasmonic gold nanoparticles. Taking advantage of the flexible control of the separate scattering and absorption channels, the influence of the absorption resonance band position on the SERS signal is also investigated. The platform shows unique potential for in vitro biosensing in thermal modulation and in situ monitoring