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Your search keyword '"Ma, Chong-Geng"' showing total 2 results
Start Over Author "Ma, Chong-Geng" Topic single crystal
2 results on '"Ma, Chong-Geng"'

1. Efficient Broadband Near-Infrared Emission from Lead-Free Halide Double Perovskite Single Crystal

Author

Zhang, Gangyi, Wang, Deyin, Lou, Bibo, Ma, Chong Geng, Meijerink, Andries, Wang, Yuhua, Sub Condensed Matter and Interfaces, and Condensed Matter and Interfaces

Subjects
All-Inorganic Perovskite, Near-Infrared Emission, Self-Trapped Excitons, Chemistry(all), Single Crystal, Catalysis
Abstract

Ultra-broadband near-infrared (NIR) luminescent materials are the most important component of NIR light-emitting devices (LED) and are crucial for their performance in sensing applications. A major challenge is to design novel NIR luminescent materials to replace the traditional Cr3+-doped systems. We report an all-inorganic bismuth halide perovskite Cs2AgBiCl6 single crystal that achieves efficient broadband NIR emission by introducing Na ions. Experiments and density functional theory (DFT) calculations show that the NIR emission originates from self-trapped excitons (STE) emission, which can be enhanced by weakening the strong coupling between electrons and phonons. The high photoluminescence quantum efficiency (PLQY) of 51 %, the extensive full width at half maximum (FWHM) of 270 nm and the stability provide advantages as a NIR luminescent material. The single-crystal-based NIR LED demonstrated its potential applications in NIR spectral detection as well as night vision.

Published
2022

2. Spectroscopic properties and martensitic phase transition of Y4Al2O9:Ce single crystals under high pressure.

Author

Wang, Yongjie, Hrubiak, R., Turczyński, S., Pawlak, D.A., Malinowski, M., Włodarczyk, D., Kosyl, K.M., Paszkowicz, W., Przybylińska, H., Wittlin, A., Kaminska, A., Zhydachevskyy, Ya, Brik, M.G., Li, Li, Ma, Chong-Geng, and Suchocki, A.

Subjects
*MARTENSITIC transformations, *YTTRIUM compounds, *CERIUM, *SINGLE crystals, *HIGH pressure (Technology), *RAMAN spectroscopy
Abstract

Abstract High pressure studies of monoclinic yttrium aluminum oxide single crystals (Y 4 Al 2 O 9 -YAM) doped with Ce3+ ions grown by micro-pulling-down method are reported. The results of absorption measurements in the mid-infrared prove the existence of four different sites in which Ce3+ ions substitute Y ions, in accordance with the crystallographic structure of YAM. The lowest 5d level of Ce3+ is located very close to the bottom of the conduction band for two of four Ce3+ related centers at ambient pressure, which results in strong temperature quenching of their luminescence. Two other Ce3+ centers do not emit at ambient pressure since their 5d levels are resonant with the conduction band. Application of high pressure above 11 GPa restores their luminescence. Consequences of such energy structure of various Ce3+ sites in YAM for the Dorenbos theory are discussed. The bandgap energy of YAM is found to be 5.93 eV, which is the smallest out of the three yttrium aluminum oxides. High-pressure synchrotron angle dispersive x-ray diffraction and Raman scattering measurements identify a phase transition occurring at pressures between 8 and 11 GPa, which has martensitic character. The second phase transition to another structure (likely with hexagonal symmetry) occurs at a pressure around 16 GPa. Graphical abstract Image 1 [ABSTRACT FROM AUTHOR]

Published
2019
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