Abstract
Despite important advances in the synthesis of inorganic perovskite nanocrystals (NCs), the long-term instability and degradation of their quantum yield (QY) over time need to be addressed to enable the further development and exploitation of these nanomaterials. Here we report stable CsPbI3 perovskite NCs and their use in hybrid light emitting diodes (LEDs), which combine in one system the NCs and a blue GaN-based LED. Nanocrystals with improved morphological and optical properties are obtained by optimizing the post-synthesis replacement of oleic acid ligands with iminodibenzoic acid: the NCs have a long shelf-life (>2 months), stability under different environmental conditions, and a high QY, of up to 90%, in the visible spectral range. Ligand replacement enables the engineering of the morphological and optical properties of the NCs. Furthermore, the NCs can be used to coat the surface of a GaN-LED to realize a stable diode where they are excited by blue light from the LED under low current injection conditions, resulting in emissions at distinct wavelengths in the visible range. The high QY and fluorescence lifetime in the nanosecond range are key parameters for visible light communication, an emerging technology that requires high-performance visible light sources for secure, fast energy-efficient wireless transmission.
Highlights
The development of colloidal halide perovskite nanocrystals (NCs) has attracted global attention since their first synthesis in 2015.1 Of particular interest are all-inorganic cesium lead halide perovskite NCs (CsPbX3, X = Cl, Br, and I or mixed)
We demonstrate the successful implementation of these NCs in a novel type of hybrid light emitting device (Fig. 1b), where the NCs coat the surface of a GaN-based light emitting diodes (LEDs)
The energy-dispersive X-ray (EDX) and X-ray photoelectron spectroscopy (XPS) studies on control and IDAtreated NCs reveal the elements and stoichiometry expected for CsPbI3 (ESI SI1†)
Summary
The stability of CsPbX3 NCs is affected by the strength of binding, surface density and stability of the capping molecules. Bidentate ligands, such as iminodibenzoic acid (IDA) and didodecyldimethylammonium bromide (DDAB), can improve the NC stability due to their coordination to two sites on the NC surface and a stronger steric effect.[18,19] the effects of replacement conditions on the stability and properties of the NCs remain unexplored. We use bidentate 2,2′-iminodibenzoic acid (IDA) ligands to replace oleic acid (Fig. 1a) and examine the effect of replacement conditions (quantity of the ligands and replacement temperature) on the stability and QY of the NCs. Optimization of the conditions for ligand replacement enables us to achieve a significant increase of the NC shelf life and QY, and stability of the NCs under different environmental conditions. The high QY and short fluorescence lifetime of the NCs are directly relevant to visible light communication (VLC), an emerging technology that requires high-performance visible light sources for secure, fast and energyefficient wireless transmission.[27]
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