Metal-halide perovskites have rapidly
emerged as one of the most
promising materials of the 21st century, with many exciting properties
and great potential for a broad range of applications, from photovoltaics
to optoelectronics and photocatalysis. The ease with which metal-halide
perovskites can be synthesized in the form of brightly luminescent
colloidal nanocrystals, as well as their tunable and intriguing optical
and electronic properties, has attracted researchers from different
disciplines of science and technology. In the last few years, there
has been a significant progress in the shape-controlled synthesis
of perovskite nanocrystals and understanding of their properties and
applications. In this comprehensive review, researchers having expertise
in different fields (chemistry, physics, and device engineering) of
metal-halide perovskite nanocrystals have joined together to provide
a state of the art overview and future prospects of metal-halide perovskite
nanocrystal research.
The easily tunable emission of halide perovskite nanocrystals throughout the visible spectrum makes them an extremely promising material for light-emitting applications. Whereas high quantum yields and long-term colloidal stability have already been achieved for nanocrystals emitting in the red and green spectral range, the blue region currently lags behind with low quantum yields, broad emission profiles, and insufficient colloidal stability. In this work, we present a facile synthetic approach for obtaining two-dimensional CsPbBr nanoplatelets with monolayer-precise control over their thickness, resulting in sharp photoluminescence and electroluminescence peaks with a tunable emission wavelength between 432 and 497 nm due to quantum confinement. Subsequent addition of a PbBr-ligand solution repairs surface defects likely stemming from bromide and lead vacancies in a subensemble of weakly emissive nanoplatelets. The overall photoluminescence quantum yield of the blue-emissive colloidal dispersions is consequently enhanced up to a value of 73 ± 2%. Transient optical spectroscopy measurements focusing on the excitonic resonances further confirm the proposed repair process. Additionally, the high stability of these nanoplatelets in films and to prolonged ultraviolet light exposure is shown.
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