A new nanocrystalline sensitizer with the chemical formula (CH₃CH₂NH₃)PbI₃ is synthesized by reacting ethylammonium iodide with lead iodide, and its crystal structure and photovoltaic property are investigated. X-ray diffraction analysis confirms orthorhombic crystal phase with a = 8.7419(2) Å, b = 8.14745(10) Å, and c = 30.3096(6) Å, which can be described as 2 H perovskite structure. Ultraviolet photoelectron spectroscopy and UV-visible spectroscopy determine the valence band position at 5.6 eV versus vacuum and the optical bandgap of ca. 2.2 eV. A spin coating of the CH₃CH₂NH₃I and PbI₂ mixed solution on a TiO₂ film yields ca. 1.8-nm-diameter (CH₃CH₂NH₃)PbI₃ dots on the TiO₂ surface. The (CH₃CH₂NH₃)PbI₃-sensitized solar cell with iodide-based redox electrolyte demonstrates the conversion efficiency of 2.4% under AM 1.5 G one sun (100 mW/cm²) illumination.

Recently, organic–inorganic halide perovskite (OHP) has been suggested as an alternative to oxides or chalcogenides in resistive switching memory devices due to low operating voltage, high ON/OFF ratio, and flexibility. The most studied OHP is 3-dimensional (3D) MAPbI₃. However, MAPbI₃ often exhibits less reliable switching behavior probably due to the uncontrollable random formation of conducting filaments. Here, we report the resistive switching property of 2-dimensional (2D) OHP and compare switching characteristics depending on structural dimensionality. The dimensionality is controlled by changing the composition of BA₂MA_n−1Pb_nI_3n+1 (BA = butylammonium, MA = methylammonium), where 2D is formed from n = 1, and 3D is formed from n = ∞. Quasi 2D compositions with n = 2 and 3 are also compared. Transition from a high resistance state (HRS) to a low resistance state (LRS) occurs at 0.25 × 10⁶ V m⁻¹ for 2D BA₂PbI₄ film, which is lower than those for quasi 2D and 3D. Upon reducing the dimensionality from 3D to 2D, the ON/OFF ratio significantly increases from 10² to 10⁷, which is mainly due to the decreased HRS current. A higher Schottky barrier and thermal activation energy are responsible for the low HRS current. We demonstrate for the first time reliable resistive switching from 4 inch wafer-scale BA₂PbI₄ thin film working at both room temperature and a high temperature of 87 °C, which strongly suggests that 2D OHP is a promising candidate for resistive switching memory.

A blue-emitting SiO ₂ :Eu ²⁺ compound has been successfully synthesized and characterized.

A new Li-ion conducting oxide, LiTa₂PO₈ with a novel three-dimensional framework structure was synthesized and characterized.

A novel blue-emitting phosphor on a phosphate-based host matrix, RbBaPO₄:Eu²⁺ (RBP), was synthesized by a solid-state reaction. This phosphor could be excited efficiently by ultra violet-visible light in the 220–420 nm range to exhibit a highly efficient emission peak in the range of 420–440 nm. To investigate the possibility of commercial use, it was compared with the commercial blue phosphors of BaMgAl₁₀O₁₇:Eu²⁺ (BAM) and Sr₃MgSi₂O₈:Eu²⁺ (SMS) to assess the photoluminescence properties. Compared to commercial phosphors, RBP displayed enhanced photoluminescence properties, in this case a high quantum efficiency and excellent thermal stability under near-Ultra Violet (n-UV) excitation. Furthermore, bright white light-emitting diodes (LEDs) were fabricated by integrating the RBP phosphor, along with commercial green/red phosphors, into n-UV LEDs. These results strongly suggest that the newly discovered RBP phosphor can be commercially utilized in UV-based white LEDs.