Long-lasting photoluminescence quantum yield of cesium lead halide perovskite-type quantum dots

Cesium lead halide perovskite (CsPbX3, X = Cl, Br, I) quantum dots (QDs) and their partly Mn2+-substituted QDs (CsPb1-xMnxX3) attract considerable attention owing to their unique photoluminescence (PL) efficiencies. The two types of QDs, having different PL decay dynamics, needed to be further investigated in a form of aggregates to understand their solid-state-induced exciton dynamics in conjunction with their behaviors upon degradation to achieve practical applications of those promising QDs. However, thus far, these QDs have not been sufficiently investigated to obtain deep insights related to the long-term stability of their PL properties as aggregated solid-states. Therefore, in this study, we comparatively examined CsPbX3- and CsPb1-xMnxX3-type QDs stocked for >50 d under dark ambient conditions by using excitation wavelength-dependent PL quantum yield and time-resolved PL spectroscopy. These investigations were performed with powder samples in addition to solutions to determine the influence of the inter-QD interaction of the aged QD aggregates on their radiative decays. It turns out that the Mn2+-substituted QDs exhibited long-lasting PL quantum efficiencies, while the unsubstituted CsPbX3-type QDs exhibited a drastic reduction of their PL efficiencies. And the obtained PL traces were clearly sensitive to the sample status. This is discussed with the possible interaction depending on the size and distance of the QD aggregates.