2021 Fiscal Year Annual Research Report
Study of electroluminescence and photophysical properties of single halide perovskite nanocrystals
| Project/Area Number |
19H02684
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| Research Institution | Tokyo Institute of Technology |
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Principal Investigator |
VACHA Martin 東京工業大学, 物質理工学院, 教授 (50361746)
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| Project Period (FY) |
2019-04-01 – 2024-03-31
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| Keywords | 単一分子分光 |
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| Outline of Annual Research Achievements |
The purpose of the project is to study the basic photophysical properties of single halide perovskite nanocrystals by photoluminescence and electroluminescence single-particle spectroscopy, with the perspective of development towards nanoscale light-emitting optoelectronic devices. The methodology is based on measurement and analysis of emission intensity time traces, spectra and excited state lifetimes. The key questions include origin and methods of suppression of blinking in both EL and PL, origin of spectral diffusion in relationship with structural/compositional stability, and effect of surface functionalization and nanocrystal orientation on the effectivity of charge transport and charge recombination.
In the past year, the research on the mechanism and methods of suppression of PL blinking included ligand engineering of the CsPbBr3 nanocrystals. The commonly used oleylamine ligands, which passivate the surface of the nanocrystals as a result of the synthesis process, were replaced by less bulky DDAB ligands. The ligand exchange had a profound effect on the PL blinking, causing a desired extension of the PL on-times (periods without the loss of PL intensity). Further, EL devices showing the potential of detecting EL signal from individual nanocrystals were fabricated and optimized with respect to charge injection and transport. In another direction of the research, a series of mixed cation (MA/FA) hybrid organo-metallic halide perovskite films were fabricated and the initial PL studies revealed the presence of PL blinking as well as nanoscale structural heterogeneity.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
The study of the origin and control of PL and EL blinking in single perovskite nanocrystals proceeded mainly according to the original plan. In particular, the ligand exchange showed a strong positive effect on the PL blinking, and the successful fabrication of the single-nanocrystal EL device opens the way to the detailed study of EL blinking mechanism. On the other hand, the preparation for the photon anti-bunching experiments has been delayed by the limited availability of photon detectors.
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| Strategy for Future Research Activity |
This year, the study of the mechanism of EL and PL blinking will continue, with the aim to demonstrate the phenomenon of photon antibunching. The blinking studies will be accompanied by monitoring of emission spectra and their time evolution. In addition to the ligand-exchange carried out, the blinking phenomena will be further controlled by exchange with other types of ligands, and by using perovskite nanocrystals (mainly CsPbBr3) embedded in metal organic frameworks. Work will also continue on the series of mixed cation (MA/FA) hybrid organo-metallic halide perovskite films by detailed study of the nanoscale structural heterogeneity and non-radiative charge traps by monitoring PL spectra and blinking. Further, the stability and the non-radiative processes of the perovskite films will be studied under an externally applied electric field to simulate conditions in real operating perovskite solar cells.
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