| 研究実績の概要 |
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, research concentrated on elucidation of the blinking mechanism in single nanocrystals of CsPbBr3. The nanocrystals were dispersed in inert polymers such as PMMA and PS, as well as in conducting matrices such as PVK or small-molecule films such as PBD or TAZ. Excitation intensity dependence of the blinking phenomenon showed that while for the inert matrices increasing intensity leads to shorter on-time periods, in the conducting matrices an opposite trend, i.e. longer on-time periods with increasing intensity, was observed. These opposite trends reflect different mechanisms of blinking. In the inert matrices the blinking is caused by the well-known Auger process. In the conducting matrices the results point to a novel blinking mechanism that includes electron transfer from the matrix to the valence band of the excited perovskite nanocrystal.
|
| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
The study of the origin of photoluminescence blinking in single perovskite nanocrystals proceeded mainly according to the original plan. Use of different matrices for the nanocrystals of CsPbBr3 perovskites made it possible to decompose the contributions of Auger recombination and charge transfer on the blinking origin, and identify a novel mechanism involving electron transfer to the valence band of the nanocrystals. On the other hand, the study of the blinking phenomenon in electroluminescence was delayed by a breakdown and repair of the film evaporation system, and the study in now ongoing.
|
| 今後の研究の推進方策 |
This year, the work on elucidating the mechanism of blinking in electroluminescence will continue, with the aim to demonstrate the phenomenon of photon antibunching in both electro- and photoluminescence. The blinking studies will be accompanied by monitoring of emission spectra and their time evolution. Further, the studies will be extended beyond the initial system of CsPbBr3 nanocrystals towards films of organic-inorganic halide perovskites. Such films are also known to exhibit the phenomenon of blinking, the origin of which is largely unknown. On the other hand, the blinking reflects the existence non-radiative decay channels which ultimately downgrade the performance of such films in solar cells. The research will aim at revealing the microscopic origin of blinking and spectral changes in films of mixed lead iodide perovskites containing varying ratio of MA and FA organic ions.
|
