The origin of green emission in the zero-dimensional (0D) perovskite Cs4PbBr6 nanocrystals (NCs) remains a considerable debate. Herein, an approach involving a combination of high-pressure experiments and theoretical simulation was employed to elucidate the controversial origin of photoluminescence from emissive Cs4PbBr6 NCs (E416). Results obtained from first-principles density functional theory (DFT) calculations, as implemented in the Vienna ab initio simulation package codes, implied that the photoluminescence energies from bromine vacancy decreased persistently with pressure. Experimentally, the photoluminescence energies tended to decrease in the low-pressure region, followed by an increase beyond ～1.4 GPa. While the emergent disagreement between the first-principles calculation and high-pressure experiment excludes the possibility of vacancy-tuning, the consistent change observed in the pressure-dependent emission between E416 and CsPbBr3 NCs offered a reliable interpretation for the occurrence of green emission from a CsPbBr3 impurity embedded in the Cs4PbBr6 matrix. Further comprehensive analysis demonstrated that the strong green emission of E416 NCs originated from the impurity CsPbBr3 NCs embedded in Cs4PbBr6 matrix. Our study represents a significant step forward to a deeper understanding of the emissive origins of Cs4PbBr6 NCs and promotes the application of this novel strategy in light-emitting devices.

中文翻译：

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Cs4PbBr6纳米晶体的发射与否：高压实验证据

零维（0D）钙钛矿Cs4PbBr6纳米晶体（NC）中绿色发射的起源仍然是一个有争议的问题。在本文中，采用了将高压实验和理论模拟相结合的方法来阐明有争议的Cs4PbBr6 NCs（E416）的光致发光起源。从第一原理密度泛函理论（DFT）计算获得的结果（如在维也纳从头算起的程序包代码中所实施的）表明，溴空位的光致发光能量随压力持续降低。在实验中，低压区域的光致发光能量趋于降低，然后升高至超过〜1.4 GPa。尽管第一性原理计算和高压实验之间出现了新的分歧，排除了空位调整的可能性，但在E416和CsPbBr3 NCs的压力依赖性排放中观察到的一致变化为从绿色气体中产生绿色排放提供了可靠的解释。 CsPbBr3杂质嵌入Cs4PbBr6基质中。进一步的综合分析表明，E416 NCs的强绿色发射源于嵌入Cs4PbBr6基质中的杂质CsPbBr3 NCs。我们的研究代表了对Cs4PbBr6 NCs发射源的更深理解的重要一步，并促进了这种新颖策略在发光器件中的应用。在E416和CsPbBr3 NC之间的压力依赖性发射中观察到的一致变化，为嵌入Cs4PbBr6基质中的CsPbBr3杂质产生绿色发射提供了可靠的解释。进一步的综合分析表明，E416 NCs的强绿色发射源于嵌入Cs4PbBr6基质中的杂质CsPbBr3 NCs。我们的研究代表了对深入了解Cs4PbBr6 NC的发射起源的重要一步，并促进了这种新颖策略在发光器件中的应用。在E416和CsPbBr3 NC之间的压力依赖性发射中观察到的一致变化，为嵌入Cs4PbBr6基质中的CsPbBr3杂质产生绿色发射提供了可靠的解释。进一步的综合分析表明，E416 NCs的强绿色发射源于嵌入Cs4PbBr6基质中的杂质CsPbBr3 NCs。我们的研究代表了对深入了解Cs4PbBr6 NC的发射起源的重要一步，并促进了这种新颖策略在发光器件中的应用。