Przystupa Krzysztof, Chornodolskyy Yaroslav M, Selech Jarosław, Karnaushenko Vladyslav O, Demkiv Taras M, Kochan Orest, Syrotyuk Stepan V, Voloshinovskii Anatolii S
Department of Automation, Lublin University of Technology, Nadbystrzycka 38D, 20-618 Lublin, Poland.
Physical Faculty, Ivan Franko National University of Lviv, 79005 Lviv, Ukraine.
Materials (Basel). 2023 Jul 19;16(14):5085. doi: 10.3390/ma16145085.
This study aims to determine the optimum composition of the CeBrI compound to achieve the maximum light output. It is based on calculations of the band energy structure of crystals, specifically taking into account the characteristics of the mutual location of local and band 5d states of the Ce ions. The band energy structures for CeBrI and CeBrI crystals were calculated using the projector augmented wave method. The valence band was found to be formed by the hybridized states of 4p Br and 5p I. The 4f states of Ce are located in the energy forbidden band gap. The conduction band is formed by the localized 5d1 states, which are created by the interaction between the 5d states of Ce and the 4f hole of the cerium ion. The higher-lying delocalized 5d2 states of Ce correspond to the energy levels of the 5d states of Ce in the field of the halide Cl (Br) hole. The relative location of 5d1 and 5d2 bands determines the intensity of 5d-4f luminescence. The bottom of the conduction band is formed by localized 5d1 states in the CeBrI crystal. The local character of the bottom of the conduction band in the CeBrI crystal favors the formation of self-trapped Frenkel excitons. Transitions between the 5d1 and 4f states are responsible for 5d-4f exciton luminescence. In the CeBrI crystal, the conduction band is formed by mixing the localized 5d1 and delocalized 5d2 states, which leads to quenching the 5d-4f luminescence and a decrease in the light output despite the decrease in the forbidden band gap. CsBrI is the optimum composition of the system to achieve the maximum light output.
本研究旨在确定溴碘化铈（CeBrI）化合物的最佳组成，以实现最大光输出。它基于晶体能带结构的计算，特别考虑了铈离子的局域和能带5d态相互位置的特征。使用投影增强波方法计算了CeBrI和CeBrI晶体的能带结构。发现价带由4p溴（Br）和5p碘（I）的杂化态形成。铈（Ce）的4f态位于禁带中。导带由局域化的5d1态形成，这些态是由Ce的5d态与铈离子的4f空穴之间的相互作用产生的。Ce的较高能离域5d2态对应于卤化物氯（Cl）（溴）空穴场中Ce的5d态能级。5d1和5d2能带的相对位置决定了5d - 4f发光的强度。CeBrI晶体中导带底部由局域化的5d1态形成。CeBrI晶体中导带底部的局域特性有利于自陷弗伦克尔激子的形成。5d1和4f态之间的跃迁导致5d - 4f激子发光。在CeBrI晶体中，导带由局域化的5d1态和离域化的5d2态混合形成，这导致5d - 4f发光猝灭以及光输出降低，尽管禁带宽度减小。溴碘化铯（CsBrI）是该体系实现最大光输出的最佳组成。
