Davidson School of Chemical Engineering, Purdue University, West Lafayette, IN, USA.
Key Laboratory of Photochemistry, Institute of Chemistry, Chinese Academy of Sciences, Beijing, China.
Nature. 2024 Sep;633(8030):567-574. doi: 10.1038/s41586-024-07925-9. Epub 2024 Sep 11.
Intermolecular distance largely determines the optoelectronic properties of organic matter. Conventional organic luminescent molecules are commonly used either as aggregates or as single molecules that are diluted in a foreigner matrix. They have garnered great research interest in recent decades for a variety of applications, including light-emitting diodes, lasers and quantum technologies, among others. However, there is still a knowledge gap on how these molecules behave between the aggregation and dilution states. Here we report an unprecedented phase of molecular aggregate that forms in a two-dimensional hybrid perovskite superlattice with a near-equilibrium distance, which we refer to as a single-molecule-like aggregate (SMA). By implementing two-dimensional superlattices, the organic emitters are held in proximity, but, surprisingly, remain electronically isolated, thereby resulting in a near-unity photoluminescence quantum yield, akin to that of single molecules. Moreover, the emitters within the perovskite superlattices demonstrate strong alignment and dense packing resembling aggregates, allowing for the observation of robust directional emission, substantially enhanced radiative recombination and efficient lasing. Molecular dynamics simulations together with single-crystal structure analysis emphasize the critical role of the internal rotational and vibrational degrees of freedom of the molecules in the two-dimensional lattice for creating the exclusive SMA phase. This two-dimensional superlattice unifies the paradoxical properties of single molecules and aggregates, thus offering exciting possibilities for advanced spectroscopic and photonic applications.
分子间距离在很大程度上决定了有机物的光电性质。传统的有机发光分子通常作为聚集态或在基质中稀释的单分子使用。近几十年来，它们在各种应用中引起了极大的研究兴趣，包括发光二极管、激光和量子技术等。然而，对于这些分子在聚集态和稀释态之间的行为，仍然存在知识上的差距。在这里，我们报告了一种前所未有的分子聚集相，它在具有近平衡距离的二维混合钙钛矿超晶格中形成，我们称之为单分子样聚集相（SMA）。通过实现二维超晶格，有机发光体保持在接近的位置，但令人惊讶的是，它们仍然保持电子隔离，从而导致近 1 的光致发光量子产率，类似于单分子。此外，钙钛矿超晶格中的发射器表现出类似于聚集态的强烈排列和密集堆积，从而允许观察到强的定向发射、显著增强的辐射复合和有效的激光。分子动力学模拟以及单晶结构分析强调了分子在二维晶格中内部旋转和振动自由度的关键作用，对于创建独特的 SMA 相至关重要。这种二维超晶格统一了单分子和聚集态的矛盾性质，从而为先进的光谱和光子学应用提供了令人兴奋的可能性。
