Highly Luminescent Cs–Pb–Br Composite Perovskites Designed via Tracking the Phase Competition During Mechanochemical Synthesis

Metal-halide perovskite particles embedded within an insulating host matrix has proven to be a potential emerging class of light emitters [1]. Particularly, outstanding luminescence properties observed in a nominally pure zero-dimensional cesium–lead–bromide perovskite (Cs₄PbBr₆) have been intensively studied due to their high quantum yield, narrow full width at half maximum, in addition to an elusive structural origin behind their bright green emission [2,3,4]. However, the rapid nature of conventional solution-based synthesis methods has limited access to mechanistic insights underlying the reaction process. In this study, we investigated the formation mechanism of Cs₄PbBr₆ by investigating the time evolution of mechanochemical synthesis process [5]. A full characterization of the phase competition between various Cs–Pb–Br intermediates during the synthesis supports the three-dimensional emitters embedded in the Cs₄PbBr₆ host as the origin of the bright emission. Furthermore, the growth mechanism proposed in our study enabled us to design synthesis routes that can enhance emission efficiency by promoting a directional growth of Cs₄PbBr₆, and therefore providing key insights for understanding and designing guided-syntheses of highly luminescent perovskite light emitters.<br/>Reference:<br/>[1] Akkerman, Q. A. et. al. <i>Nat. Mater.</i> <b>17</b>, 394–405 (2018).<br/>[2] Wang, L. et. al. <i>ACS Energy Lett.</i> <b>5</b>, 87–99 (2020).<br/>[3] Qin, Z. et al. <i>Chem. Mater.</i> <b>31</b>, 9098–9104 (2019).<br/>[4] Akkerman, Q. A. et. al. <i>J. Phys. Chem. Lett.</i> 9, 2326–2337 (2018).<br/>[5] Baek, K.-Y. et. al. (In preparation)