Kumar Sarath, Dunn Ian S, Deng Shibin, Zhu Tong, Zhao Qiuchen, Williams Olivia F, Tempelaar Roel, Huang Libai
Department of Chemistry, Purdue University, West Lafayette, IN, USA.
Department of Chemistry, Columbia University, New York, NY, USA.
Nat Chem. 2023 Aug;15(8):1118-1126. doi: 10.1038/s41557-023-01233-x. Epub 2023 Jun 19.
Exciton-exciton annihilation (EEA), an important loss channel in optoelectronic devices and photosynthetic complexes, has conventionally been assumed to be an incoherent, diffusion-limited process. Here we challenge this assumption by experimentally demonstrating the ability to control EEA in molecular aggregates using the quantum phase relationships of excitons. We employed time-resolved photoluminescence microscopy to independently determine exciton diffusion constants and annihilation rates in two substituted perylene diimide aggregates featuring contrasting excitonic phase envelopes. Low-temperature EEA rates were found to differ by more than two orders of magnitude for the two compounds, despite comparable diffusion constants. Simulated rates based on a microscopic theory, in excellent agreement with experiments, rationalize this EEA behaviour based on quantum interference arising from the presence or absence of spatial phase oscillations of delocalized excitons. These results offer an approach for designing molecular materials using quantum interference where low annihilation can coexist with high exciton concentrations and mobilities.
激子-激子湮灭（EEA）是光电器件和光合复合物中的一个重要损耗通道，传统上被认为是一个非相干的、扩散受限的过程。在此，我们通过实验证明利用激子的量子相位关系来控制分子聚集体中的EEA的能力，从而对这一假设提出挑战。我们采用时间分辨光致发光显微镜，独立测定了两种具有对比性激子相位包络的取代苝二酰亚胺聚集体中的激子扩散常数和湮灭率。尽管扩散常数相当，但发现这两种化合物在低温下的EEA速率相差两个多数量级。基于微观理论的模拟速率与实验结果高度吻合，根据离域激子空间相位振荡的存在与否所产生的量子干涉，对这种EEA行为进行了合理化解释。这些结果提供了一种利用量子干涉设计分子材料的方法，在这种方法中，低湮灭可以与高激子浓度和迁移率共存。
