Long-Lived Dark Exciton Emission in Mn-Doped CsPbCl3 Perovskite Nanocrystals
Long-Lived Dark Exciton Emission in Mn-Doped CsPbCl3 Perovskite Nanocrystals
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DOI：
10.1021/acs.jpcc.8b12035
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发表时间：
2018-12
期刊：
影响因子：
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通讯作者：
Kunyuan Xu;Jara F Vliem;A. Meijerink
中科院分区：
文献类型：
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作者：
Kunyuan Xu;Jara F Vliem;A. Meijerink
CsPbX3 钙钛矿纳米晶体 (NC) 中激子发射衰减的异常温度依赖性引起了广泛关注。冷却后，观察到极短（亚纳秒）的寿命，并通过反转的明暗态分裂来解释。在这里，我们报告了掺杂 0-41% Mn2+ 的 CsPbCl3 NC 的温度依赖性激子寿命。激子发射寿命在从 300 K 冷却到 75 K 时增加。进一步冷却后，会形成强而快速的亚纳秒衰变成分。然而，衰变是强双指数的，并且在低于 20 K 的温度下观察到弱的、缓慢的衰变成分，其寿命约为 40-50 ns。与未掺杂的 CsPbCl3 NC 相比，Mn 掺杂 NC 中的慢成分的相对强度强~5-10 倍。慢组分的温度依赖性类似于 CdSe 和 PbSe 量子点的温度依赖性，其暗-亮态分裂的激活能为 ∼19 meV。根据我们的观察，我们对 CsPbX3 NC 中短的亚纳秒激子衰减时间提出了另一种解释。低温下缓慢的明暗态弛豫几乎完全产生亮态发射。 Mn2+或高磁场的结合增强了明暗态弛豫，并允许在低温下观察长寿命的暗态发射。
The unusual temperature dependence of exciton emission decay in CsPbX3 perovskite nanocrystals (NCs) attracts considerable attention. Upon cooling, extremely short (sub-ns) lifetimes were observed and were explained by an inverted bright–dark state splitting. Here, we report temperature-dependent exciton lifetimes for CsPbCl3 NCs doped with 0–41% Mn2+. The exciton emission lifetime increases upon cooling from 300 to 75 K. Upon further cooling, a strong and fast sub-ns decay component develops. However, the decay is strongly biexponential and also a weak, slow decay component is observed with a ∼40–50 ns lifetime below 20 K. The slow component has a ∼5–10 times stronger relative intensity in Mn-doped NCs compared to that in undoped CsPbCl3 NCs. The temperature dependence of the slow component resembles that of CdSe and PbSe quantum dots with an activation energy of ∼19 meV for the dark–bright state splitting. Based on our observations, we propose an alternative explanation for the short, sub-ns exciton decay time in CsPbX3 NCs. Slow bright–dark state relaxation at cryogenic temperatures gives rise to almost exclusively bright state emission. Incorporation of Mn2+ or high magnetic fields enhances the bright–dark state relaxation and allows for the observation of the long-lived dark state emission at cryogenic temperatures.