2022 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 | Perovskite nanocrystals |
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| Outline of Annual Research Achievements |
In the past year, the research on the mechanism and methods of suppression of PL blinking included ligand engineering of the CsPbBr3 nanocrystals. Focus was placed on reproducibility of the nanocrystal synthesis and ligand exchange, as well as on the effect of the ligands on the nanocrystal aging. Further, a series of mixed cation (MA/FA) hybrid organo-metallic halide perovskite films were fabricated and their nanoscale properties were studied using PL microspectroscopy. PL spectra measured on sub-micrometer revealed large compositional heterogeneity of the films. The heterogeneity was largest for the FA 50% fraction films which contain purely MA domains, purely FA domains, as well as domains composed of mixed MA/FA cations of varying ratios. The films also showed PL blinking which reflects dynamic non-radiative quenching. The quenching was most suppressed for the FA 50% films which indicates that the truly mixed MA/FA domains are least affected by the non-radiative losses. Further, the PL blinking was correlated between locations that are several micrometers apart, indicating that the grain boundaries do not represent barriers for charge transport and do not work as charge traps, enabling efficient charge migration over micrometer distances. The blinking behavior was also affected by externally applied electric field, which additionally causes large fluctuations of PL spectra that are explained by field-induced I- ion migration.
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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 addition, unexpected results on PL blinking were observed even in hybrid perovskite films.
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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. In addition to the ligand-exchange, the stability and surface passivation of the CsPbX3 (X = Cl, Br) nanocrystals will be further controlled by incorporation into metal organic frameworks (MOFs). We will explore the effect of local ionic environment on individual nanocrystal formation and growth kinetics. Preliminary results show that the composition of the MOFs plays a dominant role in the perovskite compositional heterogeneity. Both blue and red dynamic spectral shifts indicate that collective ion migration in the hybrid systems affects the long term stability of the complexes.
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