Fabrication of 2D perovskite nanoparticles by LARP method
Hiroki Nagasaka a, Masahiro Yoshizawa-Fujita a, Naoki Shimosako a, Hideyuki Kunugita a, Kazuhiro Ema a, Yuko Takeoka a, Masahiro Rikukawa a
a Faculty of Science and Technology, Sophia University, Japan
nanoGe Perovskite Conferences
Proceedings of International Conference on Perovskite Thin Film Photovoltaics and Perovskite Photonics and Optoelectronics (NIPHO20)
Sevilla, Spain, 2020 February 23rd - 25th
Organizer: Hernán Míguez
Poster, Hiroki Nagasaka, 097
Publication date: 25th November 2019

Organic-inorganic perovskite compounds consist of lead halide octahedra and organic cations. Structure of these materials was strongly dependent on the size of organic cations. Small cations such as methylammonium or formamidinium could form three-dimensional (3D) perovskite which has general formula of APbX3 (A = organic cation; X = halide anion), whereas large cation such as RNH3+ could form two-dimensional (2D) perovskite which has general formula of A2PbX4. 2D perovskite shows superior photoluminescence (PL) intensity and absorption compared with 3D perovskite, because of quantum-well structure. These materials were mostly used in a bulk state. In the past few years, 3D perovskite nanoparticles (P-NPs) have attracted tremendous interest as a light emitting material owing to excellent optical properties such as high photoluminescence quantum yield (PLQY) and high color purity derived from quantum size effect. There is a possibility that optical properties of 2D P-NPs could pass over 3D P-NPs. Herein, facile fabrication of 2D P-NPs was demonstrated, and their optical / physical properties were investigated.

P-NPs were fabricated by general ligand assisted reprecipitation (LARP) method. C6H13NH3Br, oleic acid, and oleylamine were mixed in 1-octadecene and heated at 80°C. N, N-Dimethylformamide solution of CH3NH3Br and PbBr2 was prepared under ambient atmosphere, and heated at 80°C, respectively. These solutions were added into the 1-octadecene solution. After 1 min, chloroform was added at once. Then, the solution gradually turned from colorless to yellow with narrow blue PL emission, suggesting the formation of P-NPs. After 1 day, P-NPs was washed with ethyl acetate and collected by centrifugation at 10,000 rpm for 15 min. This process was repeated twice. P-NPs were dispersed in toluene. Optical properties were evaluated by UV-vis absorption and PL measurements. Full width at half maximum of absorption or PL peaks of P-NPs in toluene were 24 or 17 nm, respectively, which were derived from confined excitons in quantum-wells. PLQY of P-NPs in toluene was 75%. Thin film of P-NPs was prepared by hot casting at 80°C on a hydrophilic glass substrate. Formation of 2D P-NPs was confirmed by X-ray diffraction (XRD) and transmission electron microscopy.

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