Abstract
Lead halide perovskite quantum dots (PeQDs) have excellent optical properties, such as narrow emission spectra (FWHM: 18–30 nm), a tunable bandgap (λPL: 420–780 nm), and excellent photoluminescence quantum yields (PLQYs: >90%). PeQDs are known as a material that is easily decomposed when exposed to water in the atmosphere, resulting in causing PeQDs to lower performance. On the other hand, according to the recent reports, adding water after preparing the PeQD dispersion decomposed the PeQD surface defects, resulting in improving their PLQY. Namely, controlling the amount of assisting water during the preparation of the PeQDs is a significantly critical factor to determining their optical properties and device applications. In this paper, our research group discovered the novel effects of the small amount of water to their optical properties when preparing the PeQDs. According to the TEM Images, the PeQDs particle size was clearly increased after water-assisting. In addition, XPS measurement showed that the ratio of Br/Pb achieved to be close to three. Namely, by passivating the surface defect using Ostwald ripening, the prepared PeQDs achieved a high PLQY of over 95%.
Highlights
Accepted: 13 January 2022Lead halide perovskite quantum dots (PeQDs) have excellent optical properties, such as narrow emission spectra (FWHM: 18–30 nm) [1,2], a tunable bandgap [3,4], and excellent photoluminescence quantum yields (PLQYs: >90%) [1,5,6]
Various surface treatments have been applied to both inorganic and organic–inorganic perovskites by the ligand-assisted reprecipitation (LARP) method, and the prepared PeQDs via the LARP method could achieve a high PLQY over 70%, similar to that prepared by the hot injection (HI) method [5,19]
Ostwald ripening.of water, which clarified that their crystal growth occurred due
Summary
Lead halide perovskite quantum dots (PeQDs) have excellent optical properties, such as narrow emission spectra (FWHM: 18–30 nm) [1,2], a tunable bandgap (λPL : 420–780 nm) [3,4], and excellent photoluminescence quantum yields (PLQYs: >90%) [1,5,6]. Various surface treatments have been applied to both inorganic and organic–inorganic perovskites by the LARP method, and the prepared PeQDs via the LARP method could achieve a high PLQY over 70%, similar to that prepared by the HI method [5,19]. In the reports by Ying et al, a little water was added to the hexane dispersion with PeQDs to decompose the PeQD surface defects, resulting in the improvement of PLQY [21]. This method could be achieved with a high performance of the PeQDs in a one-pot preparation by assistance with water In detail, this method, combining the phenomenon of water decomposing PeQDs and Ostwald ripening, was proposed [22]. By passivating the surface defect using Ostwald ripening, the prepared PeQDs achieved a high PLQY of over 95%
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