ORCID Profile
0000-0002-6073-0908
Current Organisation
University of Tsukuba
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Publisher: Royal Society of Chemistry (RSC)
Date: 2016
DOI: 10.1039/C5RA21291J
Abstract: Planar CH 3 NH 3 SnBr 3 perovskite solar cells were fabricated via vapor deposition with a protection against air exposure achieved by a thick MABr overlayer.
Publisher: Springer Science and Business Media LLC
Date: 26-11-2021
DOI: 10.1038/S41427-021-00343-7
Abstract: The terahertz (THz)-wave absorption properties in organic-inorganic hybrid perovskite (OHP) materials are investigated with the in-depth development of OHP-based THz applications. In the THz range from 0.5 to 3 THz, OHPs typically show several interesting phonon modes such as transverse, longitudinal, and halogen self-vibrations. To modulate these frequencies, the density changes in defect-incorporated structures and element mixtures were tested and confirmed. In the literature, the origin of phonon modes in OHP materials have been mostly explained. However, we found new phonon vibration modes in formamidinium (FA)-based hybrid perovskite structures. FAPbI 3 single crystals, organic–inorganic hybrid perovskites, of the δ -, δ / α -mixed-, and α -phases were prepared. We intriguingly found that the δ / α -mixed-phase exhibited significant THz-wave absorption peaks at 2.0 and 2.2 THz that were not related to any phonon modes from either the δ - or α -phases, although the δ / α -mixed-phase s le was confirmed to be formed by a physical combination of the δ - and α -phases without the creation of any new chemical states. Our theoretical study performed with ab initio calculations provides an explanation for these unusual THz-wave absorption behaviors they originate from the novel vibration modes excited at the seamless interfaces in the mixed phase of FAPbI 3 .
Publisher: Springer Science and Business Media LLC
Date: 18-05-2015
DOI: 10.1038/SREP09863
Abstract: We fabricated perovskite solar cells using a triple-layer of n- type doped, intrinsic and p -type doped 2,2′,7,7′-tetrakis(N,N′-di-p-methoxyphenylamine)-9,9′-spirobifluorene (spiro-OMeTAD) ( n - i - p ) as hole transport layer (HTL) by vacuum evaporation. The doping concentration for n -type doped spiro-OMeTAD was optimized to adjust the highest occupied molecular orbital of spiro-OMeTAD to match the valence band maximum of perovskite for efficient hole extraction while maintaining a high open circuit voltage. Time-dependent solar cell performance measurements revealed significantly improved air stability for perovskite solar cells with the n - i - p structured spiro-OMeTAD HTL showing sustained efficiencies even after 840 h of air exposure.
Publisher: Springer Science and Business Media LLC
Date: 09-04-2019
DOI: 10.1038/S41598-019-42359-8
Abstract: The valid strong THz absorption at 1.58 THz was probed in the organic-inorganic hybrid perovskite thin film, CH 3 NH 3 PbI 3 , fabricated by sequential vacuum evaporation method. In usual solution-based methods such as 2-step solution and antisolvent, we observed the relatively weak two main absorption peaks at 0.95 and 1.87 THz. The measured absorption spectrum is analyzed by density-functional theory calculations. The modes at 0.95 and 1.87 THz are assigned to the Pb-I vibrations of the inorganic components in the tetragonal phase. By contrast, the origin of the 1.58 THz absorption is due to the structural deformation of Pb-I bonding at the grain boundary incorporated with a CH 3 NH 2 molecular defect.
Publisher: MDPI AG
Date: 28-06-2020
DOI: 10.3390/NANO10071253
Abstract: To start a step such as some realization of minimized and integrated devices, it requires simply understanding the surface status of hybrid perovskite on the e-beam irradiation because many commercial semiconductor devices are performed with a surface patterning process using e-beam or etching gas. The surface status of CH3NH3PbBr3 (MAPbBr3) single crystal was studied after a grazing e-beam irradiation in an ultra-high vacuum. The prepared hybrid perovskite single crystal was irradiated by the 3 degree-grazing e-beam with energy of 15 kV for 10 min using a reflection high-electron energy diffraction technique. The e-beam irradiation on the MAPbBr3 hybrid perovskite single crystal induced the deformation from MAPbBr3 into MABr, Br2, and Pb on the surface. The gas phases of MABr and Br2 are depleted from the surface and the Pb element has remained on the surface. As a result of the e-beam irradiation, it formed a polycrystalline-like phase and Pb metal particles on the surface, respectively.
Publisher: IOP Publishing
Date: 04-04-2019
Publisher: Frontiers Media SA
Date: 29-11-2018
Publisher: MDPI AG
Date: 17-08-2020
DOI: 10.3390/EN13164250
Abstract: Halide perovskite is one of the most promising semiconducting materials in a variety of fields such as solar cells, photodetectors, and light-emitting diodes. Lead halide perovskite single crystals featuring long diffusion length, high carrier mobility, large light absorption coefficient and low defect density, have been attracting increasing attention. Fundamental study of the intrinsic nature keeps revealing the superior optoelectrical properties of perovskite single crystals over their polycrystalline thin film counterparts, but to date, the device performance lags behind. The best power conversion efficiency (PCE) of single crystal-based solar cells is 21.9%, falling behind that of polycrystalline thin film solar cells (25.2%). The oversized thickness, defective surfaces, and difficulties in depositing functional layers, hinder the application of halide perovskite single crystals in optoelectronic devices. Efforts have been made to synthesize large-area single crystalline thin films directly on conductive substrates and apply defect engineering approaches to improve the surface properties. This review starts from a comprehensive introduction of the optoelectrical properties of perovskite single crystals. Then, the synthesis methods for high-quality bulk crystals and single-crystalline thin films are introduced and compared, followed by a systematic review of their optoelectronic applications including solar cells, photodetectors, and X-ray detectors. The challenges and strategical approaches for high-performance applications are summarized at the end with a brief outlook on future work.
Publisher: Wiley
Date: 12-09-2021
Abstract: Organometal perovskite single crystals have been recognized as a promising platform for high‐performance optoelectronic devices, featuring high crystallinity and stability. However, a high trap density and structural nonuniformity at the surface have been major barriers to the progress of single crystal‐based optoelectronic devices. Here, the formation of a unique nanoisland structure is reported at the surface of the facet‐controlled cuboid MAPbI 3 (MA = CH 3 NH 3 + ) single crystals through a cation interdiffusion process enabled by energetically vaporized CsI. The interdiffusion of mobile ions between the bulk and the surface is triggered by thermally activated CsI vapor, which reconstructs the surface that is rich in MA and CsI with reduced dangling bonds. Simultaneously, an array of Cs‐Pb‐rich nanoislands is constructed on the surface of the MAPbI 3 single crystals. This newly reconstructed nanoisland surface enhances the light absorbance over 50% and increases the charge carrier mobility from 56 to 93 cm 2 V −1 s −1 . As confirmed by Kelvin probe force microscopy, the nanoislands form a gradient band bending that prevents recombination of excess carriers, and thus, enhances lateral carrier transport properties. This unique engineering of the single crystal surface provides a pathway towards developing high‐quality perovskite single‐crystal surface for optoelectronic applications.
Publisher: Springer Science and Business Media LLC
Date: 03-08-2020
DOI: 10.1038/S41427-020-0235-6
Abstract: The exploration of new physical properties for various THz-based applications, such as THz-wave sensing, modulation, and imaging devices, is a key challenge in the research on organic–inorganic hybrid perovskite materials. These THz-based applications require satisfactory, sensitive, and stable absorption properties with values between 0.5 and 3 THz. To achieve these properties, candidate materials should possess a purified structure that induces regular and fixed phonon modes without any defects or impurities. CH 3 NH 3 PbBr 3 , an organic–inorganic hybrid perovskite thin film produced by a sequential vacuum evaporation method on a flexible PET substrate, was investigated in this study. Although the thin film contains only molecular defects related to CH 3 NH 2 incorporated into the perovskite structure, our THz-wave absorption measurement and first-principles simulation confirmed that these molecular defects do not influence the three phonon modes originating from the transverse vibration (0.8 THz), the longitudinal optical vibrations (1.4 THz) of the Pb–Br–Pb bonds, and the optical Br vibration (2.0 THz). After spin-casting an ultrathin PTAA polymer protective layer (5 nm) on the hybrid perovskite thin film, it was additionally observed that there was no significant effect on the phonon modes. Thus, this novel flexible organic–inorganic hybrid perovskite material is a potential candidate for THz-based applications.
Publisher: Elsevier BV
Date: 03-2021
Publisher: MDPI AG
Date: 10-04-2020
DOI: 10.3390/NANO10040721
Abstract: To control the density of a CH3NH2 molecular defect, which strongly contributed to a significant THz-wave absorption property in the CH3NH3PbI3 hybrid perovskite thin film formed by the sequential vacuum evaporation method, we performed post-annealing processes with various temperatures and times. In the thin film after post-annealing at 110 °C for 45 min, the density of the CH3NH2 molecular defect was minimized, and CH3NH3I and PbI2 disappeared in the thin film after the post-annealing process at 150 °C for 30 min. However, the density of the CH3NH2 molecular defect increased. Moreover, the THz-wave absorption property for each thin film was obtained using a THz time-domain spectroscopy to understand the correlation between the density of a molecular defect and the THz-wave oscillation strength at 1.6 THz, which originated in the molecular defect-incorporated hybrid perovskite structure. There is a strong linear correlation between the oscillator strength of a significant THz-wave absorption at 1.6 THz and the CH3NH2 molecular defect density.
Location: No location found
Location: Korea, Republic of
Location: Japan
Location: Korea, Republic of
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