2018 Fiscal Year Annual Research Report
酸化還元活性な配位高分子における磁気・電子相関の交差制御
| Project/Area Number |
18J20896
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| Research Institution | Tohoku University |
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Principal Investigator |
黄 柏融 東北大学, 理学研究科, 特別研究員(DC1)
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| Project Period (FY) |
2018-04-25 – 2021-03-31
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| Keywords | chirality / bulk photovoltaic effect / lead iodides |
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| Outline of Annual Research Achievements |
Due to the difficulty of synthesis, metal halide perovskites were investigated by inputting chirality as the source of non-centrosymmetry instead of Cr3-TCNQ derivatives. First for the optoelectric properties, chiral two-dimensional lead iodide compounds were synthesized and characterized since this class of materials is one of the high-performing photovolatic platforms.
Compounds R- and S-Pb2I7 displays optical responses under solar simulated white light that detected current under applied electric field increases in two orders. Electric polarization was discovered from crystal structure and and the detection of bulk photovoltaic effect. This is the realization of chirality-polarity coupling and the first report for the control of such property by chirality. This work will soon be published. This work has been orally reported in the spring conference of CSJ this year in Kobe.
Chiral two-dimensional copper bromide perovskites were also chosen for the investigation of magnetoelectric effect. The material shows ferromagnetic behavior under a certain temperature but behaves quite ambiguous in low magnetic field region. Under details measurements, at least four distinct phases can be roughly determined. This interesting behavior will be analyzed in detail in the future.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
Although the trial of Cr3-TCNQ compounds faced huge difficulty in synthetic aspect, perovskite-type compounds investigated instead demonstrates great progress. Control of zero-bias photocurrent in chiral bulk photovoltaic materials, and the analysis of complicate phase diagram of two-dimensional chiral magnets are both beyond the project scheduled.
Work involves lead iodides has finished and the pure chiral photovoltaic materials are now under exploration. The copper halide chiral magnets are also under investigated from the further information of magnetic structure and the existence of several phases including helical, conical, and skyrmion phases. All these is scheduled to be published in this year.
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| Strategy for Future Research Activity |
Since the old direction of project faced difficulty in the synthesis of Cr3-TCNQ derivatives, chiral two-dimensional perovskite-type materials are investigated instead. The introduction of chemical controllable chirality may easily break centrosymmetry of material, therefore, novel physical properties may possibly be controlled and rational designed. Chirality-induced photovoltaic effect, magnetoelectric effect, spin filter, and magnetic skyrmion are all objectives in the future.
Meanwhile, magnetochiral dichroism is another target to control in material systems. Copper-based metal-organic frameworks are chosen for substrate for the adsorption/desorption of chiral molecules. The switch of magnetochiral dichroism is then possible.
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