Correlating nano black spots and optical stability in mixed halide perovskite quantum dots
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초록
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Inorganic lead trihalide perovskites quantem dots (PQDs) are highly efficient emitting materials with sharp emission profiles. Among inorganic lead trihalide PQDs (CsPbX3 where X= Cl-, Br-, I-) usually show the most breathtaking PL-QY (up to 90%) in the primary observations directly after synthesis, but, also show the lowest optical stability, thereby delaying their commercialization. In fact, it takes only a few days to have totally zero-emission when they are left in air at room temperature due to the chemical degradation. The causes of this degradation potentially include factors such as thermal decomposition, light exposure and phase transitions. Our investigations based on TEM and HAADF-TEM reveal that Nano black spots (NBSs) are areas of high concentration of Pb2+ ions on the QDs. We have futher correlated the apprearance of NBSs with change in optical properties of QDs. Tolerance factor can be used to predict optical stability and appearance of NBSs.