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- 저자 : Yoonhoo Ha (검색결과 2 건)
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Yoonhoo Ha,Yoosang Son,Dooam Paik,Ki-Ha Hong,Hyungjun Kim 대한금속·재료학회 2023 ELECTRONIC MATERIALS LETTERS Vol.19 No.6
Metal halide perovskites (MHPs) have attracted considerable attentions as promising candidates for next-generation optoelectronic devices, such as light-emitting diode (LED), owing to their outstanding photophysical properties. Nanostructuring is considered an essential approach to facilitate the bright emission of MHPs, which entails an increase in the surface domain that can directly aff ect the carrier dynamics. However, a comprehensive understanding of the surface termination eff ect on the photodynamic properties of MHPs is still lacking. Herein, we systematically investigate the eff ect of surface termination on the carrier recombination dynamics of CsPbBr 3 using ab-initio non-adiabatic molecular dynamics simulations. We found separate localizations of electron and hole carriers in the vicinity of the more and less coordinated inorganic polyhedral, respectively, which can be explained by the energy level changes associated with the modifi cations in Pb–Br bond lengths and their anharmonicity. This leads to the spatial separation of charge carriers, which retards the radiative kinetics more than the non-radiative one, reducing the photoluminescence quantum yield (PLQY). We further found that the homogenous linewidth is broadened upon introduction of surface terminations. Thus, our study suggests a possible LED-performance degradation mechanism due to surface termination, and thereby proposes guidelines for enhancing the light-emission properties of nanostructured MHPs.
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Han, Jong Yoon,Choi, Tae Su,Kim, Soyoung,Lee, Jong Wha,Ha, Yoonhoo,Jeong, Kwang Seob,Kim, Hyungjun,Choi, Hee Cheul,Kim, Hugh I. American Chemical Society 2016 ANALYTICAL CHEMISTRY - Vol.88 No.16
<P>Fullerenes, cage-structured carbon allotropes, have been the subject of extensive research as new materials for diverse purposes. Yet, their formation process is still not clearly understood at the molecular level. In this study, we performed laser desorption ionization-ion mobility-mass spectrometry (LDI-IM-MS) of carbon substrates possessing different molecular sizes and structures to understand the formation process of fullerene. Our observations show that the formation process is strongly dependent on the size of the precursor used, with small precursors yielding small fullerenes and large graphitic precursors generally yielding larger fullerenes. These results clearly demonstrate that fullerene formation can proceed via both bottom-up and top-down processes, with the latter being favored for large precursors and more efficient at forming fullerenes. Furthermore, we observed that specific structures of carbon precursors could additionally affect the relative abundance of C-60, fullerene. Overall, this study provides an advanced understanding of the mechanistic details underlying the formation processes of fullerene.</P>
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