Donghwa Lee

Hysteresis and stability issues in perovskite solar cell (PSCs) hinder their commercialization. Here, we report an effective and reproducible approach for enhancing the stability of and suppressing the hysteresis in PSCs by incorporating a small quantity of two-dimensional (2D) PEA 2 PbI 4 [PEA = C 6 H 5 (CH 2 ) 2 NH 3 ] in three-dimensional (3D) MAPbI 3 [MA = CH 3 NH 3 ] [denoted as (PEA 2 PbI 4 ) x (MAPbI 3 )], where the perovskite films were fabricated by the Lewis acid–base adduct method. A

Ferroelectric $180\ifmmode^\circ\else\textdegree\fi{}$ domain walls are well-known to be predominantly Ising-like. Using density functional theory, and molecular dynamics simulations, the $180\ifmmode^\circ\else\textdegree\fi{}$ domain walls in prototypical ferroelectrics lead titanate $({\text{PbTiO}}_{3})$ and lithium niobate $({\text{LiNbO}}_{3})$ are shown to have mixed character; while predominantly Ising-like, they also manifest some Bloch- and N\'eel-like character. Phase-field calculatio

Noble metal nanoparticle decoration is a representative strategy to enhance selectivity for fabricating chemical sensor arrays based on the 2-dimensional (2D) semiconductor material, represented by molybdenum disulfide (MoS 2 ). However, the mechanism of selectivity tuning by noble metal decoration on 2D materials has not been fully elucidated. Here, we successfully decorated noble metal nanoparticles on MoS 2 flakes by the solution process without using reducing agents. The MoS 2 flakes showed

As silicon-based metal oxide semiconductor field effect transistors get closer to their scaling limit, the importance of resistive random-access memory devices increases due to their low power consumption, high endurance and retention performance, scalability, and fast switching speed. In the last couple of years, organic-inorganic lead halide perovskites have been used for resistive switching applications, where they outperformed conventional metal oxides in terms of large on/off ratio and low

Abstract Organic–inorganic halide perovskite is regarded as one of the potential candidates for next generation resistive switching memory (memristor) material because of fast, millivolt‐scale switching, multilevel capability, and high On/Off ratio. Here, resistive switching property of HC(NH 2 ) 2 PbI 3 (FAPbI 3 ) depending on structural phase is reported. It is found that 1D hexagonal FAPbI 3 (δ‐FAPbI 3 ), formed at relatively low temperature, is active in memristor, while 3D trigonal FAPbI3 (

Detection of ppb level ammonia at room temperature is demonstrated using chemically fluorinated graphene oxide (CFGO). Fluorine adatom extremely enhances ammonia sensing capabilities through the changes of the charge distributions on adjacent functional groups, resulting in the variation in gas adsorption energies.

Abstract All‐inorganic cesium lead triiodide (CsPbI 3 ) perovskite is considered a promising solution‐processable semiconductor for highly stable optoelectronic and photovoltaic applications. However, despite its excellent optoelectronic properties, the phase instability of CsPbI 3 poses a critical hurdle for practical application. In this study, a novel stain‐mediated phase stabilization strategy is demonstrated to significantly enhance the phase stability of cubic α‐phase CsPbI 3 . Careful con

Abstract Resistive switching memory that uses halide perovskites (HP) has been considered as next-generation storage devices due to low operation voltage and high on/off ratio. However, the memory still faces challenges for stable operation with fast switching speed, which hinders the practical application. Thus, it should be considered from the stage of designing the HP for memory applications. Here, we design the perovskite memory using a high-throughput screening based on first-principles cal

Metal to semiconductor transition by hole compensation of excess electrons from <italic>V</italic>_O and localized <italic>V</italic>_O state in La_0.5Sr_0.5FeO_3−δ under low <italic>P</italic>_O2.

Graphene is one of the most promising materials for high-performance gas sensors due to its unique properties such as high sensitivity at room temperature, transparency, and flexibility. However, the low selectivity and irreversible behavior of graphene-based gas sensors are major problems. Here, we present unprecedented room temperature hydrogen detection by Au nanoclusters supported on self-activated graphene. Compared to pristine graphene sensors, the Au-decorated graphene sensors exhibit hig

Atomistic simulations with empirical potentials and density-functional theory calculations are used to characterize the structure, energetics, and ferroelectric properties of domain walls in ${\text{LiNbO}}_{3}$. The two methods yield similar polarization patterns and atomic structures at the domain walls. The structure of the domain wall on the mixed anion-cation planes is very different from that of the domain wall on planes of alternating cations and anions. The breaking of the uniaxial symme

Effective methods for decoupling superconducting qubits (SQs) from parasitic environmental noise sources are critical for increasing their lifetime and phase fidelity. While considerable progress has been made in this area, the microscopic origin of noise remains largely unknown. In this work, first principles density functional theory calculations are employed to identify the microscopic origins of magnetic noise sources in SQs on an α-Al2O3 substrate. The results indicate that it is unlikely t